* [Qemu-devel] [PATCH 1/3] Introduce threadlets
2010-10-26 14:14 [Qemu-devel] v8: [PATCH 0/3] Threadlets: A generic task offloading framework Arun R Bharadwaj
@ 2010-10-26 14:14 ` Arun R Bharadwaj
2010-10-26 19:31 ` Blue Swirl
2010-11-01 13:40 ` Anthony Liguori
2010-10-26 14:14 ` [Qemu-devel] [PATCH 2/3] Make paio subsystem use threadlets Arun R Bharadwaj
2010-10-26 14:14 ` [Qemu-devel] [PATCH 3/3] Add helper functions to enable virtio-9p make use of the threadlets Arun R Bharadwaj
2 siblings, 2 replies; 8+ messages in thread
From: Arun R Bharadwaj @ 2010-10-26 14:14 UTC (permalink / raw)
To: qemu-devel
From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
This patch creates a generic asynchronous-task-offloading infrastructure named
threadlets. The core idea has been borrowed from the threading framework that
is being used by paio.
The reason for creating this generic infrastructure is so that other subsystems,
such as virtio-9p could make use of it for offloading tasks that could block.
The patch creates a global queue on-to which subsystems can queue their tasks to
be executed asynchronously.
The patch also provides API's that allow a subsystem to create a private queue
with an associated pool of threads.
[ego@in.ibm.com: Facelift of the code, Documentation, cancel_threadlet
and other helpers]
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Gautham R Shenoy <gautham.shenoy@gmail.com>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
---
Makefile.objs | 3 +
docs/async-support.txt | 141 +++++++++++++++++++++++++++++++++++++++++
qemu-threadlets.c | 167 ++++++++++++++++++++++++++++++++++++++++++++++++
qemu-threadlets.h | 48 ++++++++++++++
4 files changed, 358 insertions(+), 1 deletions(-)
create mode 100644 docs/async-support.txt
create mode 100644 qemu-threadlets.c
create mode 100644 qemu-threadlets.h
diff --git a/Makefile.objs b/Makefile.objs
index cd5a24b..2cf8aba 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -9,6 +9,8 @@ qobject-obj-y += qerror.o
block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
block-obj-y += nbd.o block.o aio.o aes.o osdep.o qemu-config.o
+block-obj-$(CONFIG_POSIX) += qemu-thread.o
+block-obj-$(CONFIG_POSIX) += qemu-threadlets.o
block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
@@ -124,7 +126,6 @@ endif
common-obj-y += $(addprefix ui/, $(ui-obj-y))
common-obj-y += iov.o acl.o
-common-obj-$(CONFIG_THREAD) += qemu-thread.o
common-obj-y += notify.o event_notifier.o
common-obj-y += qemu-timer.o
diff --git a/docs/async-support.txt b/docs/async-support.txt
new file mode 100644
index 0000000..9f22b9a
--- /dev/null
+++ b/docs/async-support.txt
@@ -0,0 +1,141 @@
+== How to use the threadlets infrastructure supported in Qemu ==
+
+== Threadlets ==
+
+Q.1: What are threadlets ?
+A.1: Threadlets is an infrastructure within QEMU that allows other subsystems
+ to offload possibly blocking work to a queue to be processed by a pool
+ of threads asynchronously.
+
+Q.2: When would one want to use threadlets ?
+A.2: Threadlets are useful when there are operations that can be performed
+ outside the context of the VCPU/IO threads inorder to free these latter
+ to service any other guest requests.
+
+Q.3: I have some work that can be executed in an asynchronous context. How
+ should I go about it ?
+A.3: One could follow the steps listed below:
+
+ - Define a function which would do the asynchronous work.
+ static void my_threadlet_func(ThreadletWork *work)
+ {
+ }
+
+ - Declare an object of type ThreadletWork;
+ ThreadletWork work;
+
+
+ - Assign a value to the "func" member of ThreadletWork object.
+ work.func = my_threadlet_func;
+
+ - Submit the threadlet to the global queue.
+ submit_threadletwork(&work);
+
+ - Continue servicing some other guest operations.
+
+Q.4: I want to my_threadlet_func to access some non-global data. How do I do
+ that ?
+A.4: Suppose you want my_threadlet_func to access some non-global data-object
+ of type myPrivateData. In that case one could follow the following steps.
+
+ - Define a member of the type ThreadletWork within myPrivateData.
+ typedef struct MyPrivateData {
+ ...;
+ ...;
+ ...;
+ ThreadletWork work;
+ } MyPrivateData;
+
+ MyPrivateData my_data;
+
+ - Initialize myData.work as described in A.3
+ myData.work.func = my_threadlet_func;
+ submit_threadletwork(&myData.work);
+
+ - Access the myData object inside my_threadlet_func() using container_of
+ primitive
+ static void my_threadlet_func(ThreadletWork *work)
+ {
+ myPrivateData *mydata_ptr;
+ mydata_ptr = container_of(work, myPrivateData, work);
+
+ /* mydata_ptr now points to myData object */
+ }
+
+Q.5: Are there any precautions one must take while sharing data with the
+ Asynchronous thread-pool ?
+A.5: Yes, make sure that the helper function of the type my_threadlet_func()
+ does not access/modify data when it can be accessed or modified in the
+ context of VCPU thread or IO thread. This is because the asynchronous
+ threads in the pool can run in parallel with the VCPU/IOThreads as shown
+ in the figure.
+
+ A typical workflow is as follows:
+
+ VCPU/IOThread
+ |
+ | (1)
+ |
+ V
+ Offload work (2)
+ |-------> to threadlets -----------------------------> Helper thread
+ | | |
+ | | |
+ | | (3) | (4)
+ | | |
+ | Handle other Guest requests |
+ | | |
+ | | V
+ | | (3) Signal the I/O Thread
+ |(6) | |
+ | | /
+ | | /
+ | V /
+ | Do the post <---------------------------------/
+ | processing (5)
+ | |
+ | | (6)
+ | V
+ |-Yes------ More async work?
+ |
+ | (7)
+ No
+ |
+ |
+ .
+ .
+
+ Hence one needs to make sure that in the steps (3) and (4) which run in
+ parallel, any global data is accessed within only one context.
+
+Q.6: I have queued a threadlet which I want to cancel. How do I do that ?
+A.6: Threadlets framework provides the API cancel_threadlet:
+ - int cancel_threadletwork(ThreadletWork *work)
+
+ The API scans the ThreadletQueue to see if (work) is present. If it finds
+ work, it'll dequeue work and return 0.
+
+ On the other hand, if it does not find the (work) in the ThreadletQueue,
+ then it'll return 1. This can imply two things. Either the work is being
+ processed by one of the helper threads or it has been processed. The
+ threadlet infrastructure currently _does_not_ distinguish between these
+ two and the onus is on the caller to do that.
+
+Q.7: Apart from the global pool of threads, can I have my own private Queue ?
+A.7: Yes, the threadlets framework allows subsystems to create their own private
+ queues with associated pools of threads.
+
+ - Define a PrivateQueue
+ ThreadletQueue myQueue;
+
+ - Initialize it:
+ threadlet_queue_init(&myQueue, my_max_threads, my_min_threads);
+ where my_max_threads is the maximum number of threads that can be in the
+ thread pool and my_min_threads is the minimum number of active threads
+ that can be in the thread-pool.
+
+ - Submit work:
+ submit_threadletwork_to_queue(&myQueue, &my_work);
+
+ - Cancel work:
+ cancel_threadletwork_on_queue(&myQueue, &my_work);
diff --git a/qemu-threadlets.c b/qemu-threadlets.c
new file mode 100644
index 0000000..8fc3be0
--- /dev/null
+++ b/qemu-threadlets.c
@@ -0,0 +1,167 @@
+/*
+ * Threadlet support for offloading tasks to be executed asynchronously
+ *
+ * Copyright IBM, Corp. 2008
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ * Anthony Liguori <aliguori@us.ibm.com>
+ * Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ * Gautham R Shenoy <gautham.shenoy@gmail.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ */
+
+#include "qemu-threadlets.h"
+#include "osdep.h"
+
+#define MAX_GLOBAL_THREADS 64
+#define MIN_GLOBAL_THREADS 64
+static ThreadletQueue globalqueue;
+static int globalqueue_init;
+
+static void *threadlet_worker(void *data)
+{
+ ThreadletQueue *queue = data;
+
+ qemu_mutex_lock(&(queue->lock));
+ while (1) {
+ ThreadletWork *work;
+ int ret = 0;
+
+ while (QTAILQ_EMPTY(&(queue->request_list)) &&
+ (ret != ETIMEDOUT)) {
+ /* wait for cond to be signalled or broadcast for 1000s */
+ ret = qemu_cond_timedwait(&(queue->cond),
+ &(queue->lock), 10*100000);
+ }
+
+ assert(queue->idle_threads != 0);
+ if (QTAILQ_EMPTY(&(queue->request_list))) {
+ if (queue->cur_threads > queue->min_threads) {
+ /* We retain the minimum number of threads */
+ break;
+ }
+ } else {
+ work = QTAILQ_FIRST(&(queue->request_list));
+ QTAILQ_REMOVE(&(queue->request_list), work, node);
+
+ queue->idle_threads--;
+ qemu_mutex_unlock(&(queue->lock));
+
+ /* execute the work function */
+ work->func(work);
+
+ qemu_mutex_lock(&(queue->lock));
+ queue->idle_threads++;
+ }
+ }
+
+ queue->idle_threads--;
+ queue->cur_threads--;
+ qemu_mutex_unlock(&(queue->lock));
+
+ return NULL;
+}
+
+static void spawn_threadlet(ThreadletQueue *queue)
+{
+ QemuThread thread;
+
+ queue->cur_threads++;
+ queue->idle_threads++;
+
+ qemu_thread_create(&thread, threadlet_worker, queue);
+}
+
+/**
+ * submit_threadletwork_to_queue: Submit a new task to a private queue to be
+ * executed asynchronously.
+ * @queue: Per-subsystem private queue to which the new task needs
+ * to be submitted.
+ * @work: Contains information about the task that needs to be submitted.
+ */
+void submit_threadletwork_to_queue(ThreadletQueue *queue, ThreadletWork *work)
+{
+ qemu_mutex_lock(&(queue->lock));
+ if (queue->idle_threads == 0 && queue->cur_threads < queue->max_threads) {
+ spawn_threadlet(queue);
+ } else {
+ qemu_cond_signal(&(queue->cond));
+ }
+ QTAILQ_INSERT_TAIL(&(queue->request_list), work, node);
+ qemu_mutex_unlock(&(queue->lock));
+}
+
+/**
+ * submit_threadletwork: Submit to the global queue a new task to be executed
+ * asynchronously.
+ * @work: Contains information about the task that needs to be submitted.
+ */
+void submit_threadletwork(ThreadletWork *work)
+{
+ if (unlikely(!globalqueue_init)) {
+ threadlet_queue_init(&globalqueue, MAX_GLOBAL_THREADS,
+ MIN_GLOBAL_THREADS);
+ globalqueue_init = 1;
+ }
+
+ submit_threadletwork_to_queue(&globalqueue, work);
+}
+
+/**
+ * deque_threadletwork_on_queue: Cancel a task queued on a Queue.
+ * @queue: The queue containing the task to be cancelled.
+ * @work: Contains the information of the task that needs to be cancelled.
+ *
+ * Returns: 0 if the task is successfully cancelled.
+ * 1 otherwise.
+ */
+int deque_threadletwork_on_queue(ThreadletQueue *queue, ThreadletWork *work)
+{
+ ThreadletWork *ret_work;
+ int ret = 1;
+
+ qemu_mutex_lock(&(queue->lock));
+ QTAILQ_FOREACH(ret_work, &(queue->request_list), node) {
+ if (ret_work == work) {
+ QTAILQ_REMOVE(&(queue->request_list), ret_work, node);
+ ret = 0;
+ break;
+ }
+ }
+ qemu_mutex_unlock(&(queue->lock));
+
+ return ret;
+}
+
+/**
+ * deque_threadletwork: Cancel a task queued on the global queue.
+ * @work: Contains the information of the task that needs to be cancelled.
+ *
+ * Returns: 0 if the task is successfully cancelled.
+ * 1 otherwise.
+ */
+int deque_threadletwork(ThreadletWork *work)
+{
+ return deque_threadletwork_on_queue(&globalqueue, work);
+}
+
+/**
+ * threadlet_queue_init: Initialize a threadlet queue.
+ * @queue: The threadlet queue to be initialized.
+ * @max_threads: Maximum number of threads processing the queue.
+ * @min_threads: Minimum number of threads processing the queue.
+ */
+void threadlet_queue_init(ThreadletQueue *queue,
+ int max_threads, int min_threads)
+{
+ queue->cur_threads = 0;
+ queue->idle_threads = 0;
+ queue->max_threads = max_threads;
+ queue->min_threads = min_threads;
+ QTAILQ_INIT(&(queue->request_list));
+ qemu_mutex_init(&(queue->lock));
+ qemu_cond_init(&(queue->cond));
+}
diff --git a/qemu-threadlets.h b/qemu-threadlets.h
new file mode 100644
index 0000000..6d9585b
--- /dev/null
+++ b/qemu-threadlets.h
@@ -0,0 +1,48 @@
+/*
+ * Threadlet support for offloading tasks to be executed asynchronously
+ *
+ * Copyright IBM, Corp. 2008
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ * Anthony Liguori <aliguori@us.ibm.com>
+ * Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ * Gautham R Shenoy <ego@in.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ */
+
+#ifndef QEMU_ASYNC_WORK_H
+#define QEMU_ASYNC_WORK_H
+
+#include "qemu-queue.h"
+#include "qemu-common.h"
+#include "qemu-thread.h"
+
+typedef struct ThreadletQueue
+{
+ QemuMutex lock;
+ QemuCond cond;
+ int max_threads;
+ int min_threads;
+ int cur_threads;
+ int idle_threads;
+ QTAILQ_HEAD(, ThreadletWork) request_list;
+} ThreadletQueue;
+
+typedef struct ThreadletWork
+{
+ QTAILQ_ENTRY(ThreadletWork) node;
+ void (*func)(struct ThreadletWork *work);
+} ThreadletWork;
+
+extern void submit_threadletwork_to_queue(ThreadletQueue *queue,
+ ThreadletWork *work);
+extern void submit_threadletwork(ThreadletWork *work);
+extern int deque_threadletwork_on_queue(ThreadletQueue *queue,
+ ThreadletWork *work);
+extern int deque_threadletwork(ThreadletWork *work);
+extern void threadlet_queue_init(ThreadletQueue *queue, int max_threads,
+ int min_threads);
+#endif
^ permalink raw reply related [flat|nested] 8+ messages in thread* Re: [Qemu-devel] [PATCH 1/3] Introduce threadlets
2010-10-26 14:14 ` [Qemu-devel] [PATCH 1/3] Introduce threadlets Arun R Bharadwaj
@ 2010-10-26 19:31 ` Blue Swirl
2010-11-01 13:40 ` Anthony Liguori
1 sibling, 0 replies; 8+ messages in thread
From: Blue Swirl @ 2010-10-26 19:31 UTC (permalink / raw)
To: Arun R Bharadwaj; +Cc: qemu-devel
On Tue, Oct 26, 2010 at 2:14 PM, Arun R Bharadwaj
<arun@linux.vnet.ibm.com> wrote:
> From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>
> This patch creates a generic asynchronous-task-offloading infrastructure named
> threadlets. The core idea has been borrowed from the threading framework that
> is being used by paio.
>
> The reason for creating this generic infrastructure is so that other subsystems,
> such as virtio-9p could make use of it for offloading tasks that could block.
>
> The patch creates a global queue on-to which subsystems can queue their tasks to
> be executed asynchronously.
>
> The patch also provides API's that allow a subsystem to create a private queue
> with an associated pool of threads.
>
> [ego@in.ibm.com: Facelift of the code, Documentation, cancel_threadlet
> and other helpers]
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> Signed-off-by: Gautham R Shenoy <gautham.shenoy@gmail.com>
> Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
> ---
> Makefile.objs | 3 +
> docs/async-support.txt | 141 +++++++++++++++++++++++++++++++++++++++++
> qemu-threadlets.c | 167 ++++++++++++++++++++++++++++++++++++++++++++++++
> qemu-threadlets.h | 48 ++++++++++++++
> 4 files changed, 358 insertions(+), 1 deletions(-)
> create mode 100644 docs/async-support.txt
> create mode 100644 qemu-threadlets.c
> create mode 100644 qemu-threadlets.h
>
> diff --git a/Makefile.objs b/Makefile.objs
> index cd5a24b..2cf8aba 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -9,6 +9,8 @@ qobject-obj-y += qerror.o
>
> block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
> block-obj-y += nbd.o block.o aio.o aes.o osdep.o qemu-config.o
> +block-obj-$(CONFIG_POSIX) += qemu-thread.o
> +block-obj-$(CONFIG_POSIX) += qemu-threadlets.o
> block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
> block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
>
> @@ -124,7 +126,6 @@ endif
> common-obj-y += $(addprefix ui/, $(ui-obj-y))
>
> common-obj-y += iov.o acl.o
> -common-obj-$(CONFIG_THREAD) += qemu-thread.o
> common-obj-y += notify.o event_notifier.o
> common-obj-y += qemu-timer.o
>
> diff --git a/docs/async-support.txt b/docs/async-support.txt
> new file mode 100644
> index 0000000..9f22b9a
> --- /dev/null
> +++ b/docs/async-support.txt
> @@ -0,0 +1,141 @@
> +== How to use the threadlets infrastructure supported in Qemu ==
> +
> +== Threadlets ==
> +
> +Q.1: What are threadlets ?
> +A.1: Threadlets is an infrastructure within QEMU that allows other subsystems
> + to offload possibly blocking work to a queue to be processed by a pool
> + of threads asynchronously.
> +
> +Q.2: When would one want to use threadlets ?
> +A.2: Threadlets are useful when there are operations that can be performed
> + outside the context of the VCPU/IO threads inorder to free these latter
> + to service any other guest requests.
> +
> +Q.3: I have some work that can be executed in an asynchronous context. How
> + should I go about it ?
> +A.3: One could follow the steps listed below:
> +
> + - Define a function which would do the asynchronous work.
> + static void my_threadlet_func(ThreadletWork *work)
> + {
> + }
> +
> + - Declare an object of type ThreadletWork;
> + ThreadletWork work;
> +
> +
> + - Assign a value to the "func" member of ThreadletWork object.
> + work.func = my_threadlet_func;
> +
> + - Submit the threadlet to the global queue.
> + submit_threadletwork(&work);
> +
> + - Continue servicing some other guest operations.
> +
> +Q.4: I want to my_threadlet_func to access some non-global data. How do I do
> + that ?
> +A.4: Suppose you want my_threadlet_func to access some non-global data-object
> + of type myPrivateData. In that case one could follow the following steps.
> +
> + - Define a member of the type ThreadletWork within myPrivateData.
> + typedef struct MyPrivateData {
> + ...;
> + ...;
> + ...;
> + ThreadletWork work;
> + } MyPrivateData;
> +
> + MyPrivateData my_data;
> +
> + - Initialize myData.work as described in A.3
> + myData.work.func = my_threadlet_func;
> + submit_threadletwork(&myData.work);
> +
> + - Access the myData object inside my_threadlet_func() using container_of
> + primitive
> + static void my_threadlet_func(ThreadletWork *work)
> + {
> + myPrivateData *mydata_ptr;
> + mydata_ptr = container_of(work, myPrivateData, work);
> +
> + /* mydata_ptr now points to myData object */
> + }
> +
> +Q.5: Are there any precautions one must take while sharing data with the
> + Asynchronous thread-pool ?
> +A.5: Yes, make sure that the helper function of the type my_threadlet_func()
> + does not access/modify data when it can be accessed or modified in the
> + context of VCPU thread or IO thread. This is because the asynchronous
> + threads in the pool can run in parallel with the VCPU/IOThreads as shown
> + in the figure.
> +
> + A typical workflow is as follows:
> +
> + VCPU/IOThread
> + |
> + | (1)
> + |
> + V
> + Offload work (2)
> + |-------> to threadlets -----------------------------> Helper thread
> + | | |
> + | | |
> + | | (3) | (4)
> + | | |
> + | Handle other Guest requests |
> + | | |
> + | | V
> + | | (3) Signal the I/O Thread
> + |(6) | |
> + | | /
> + | | /
> + | V /
> + | Do the post <---------------------------------/
> + | processing (5)
> + | |
> + | | (6)
> + | V
> + |-Yes------ More async work?
> + |
> + | (7)
> + No
> + |
> + |
> + .
> + .
> +
> + Hence one needs to make sure that in the steps (3) and (4) which run in
> + parallel, any global data is accessed within only one context.
> +
> +Q.6: I have queued a threadlet which I want to cancel. How do I do that ?
> +A.6: Threadlets framework provides the API cancel_threadlet:
> + - int cancel_threadletwork(ThreadletWork *work)
> +
> + The API scans the ThreadletQueue to see if (work) is present. If it finds
> + work, it'll dequeue work and return 0.
> +
> + On the other hand, if it does not find the (work) in the ThreadletQueue,
> + then it'll return 1. This can imply two things. Either the work is being
> + processed by one of the helper threads or it has been processed. The
> + threadlet infrastructure currently _does_not_ distinguish between these
> + two and the onus is on the caller to do that.
> +
> +Q.7: Apart from the global pool of threads, can I have my own private Queue ?
> +A.7: Yes, the threadlets framework allows subsystems to create their own private
> + queues with associated pools of threads.
> +
> + - Define a PrivateQueue
> + ThreadletQueue myQueue;
> +
> + - Initialize it:
> + threadlet_queue_init(&myQueue, my_max_threads, my_min_threads);
> + where my_max_threads is the maximum number of threads that can be in the
> + thread pool and my_min_threads is the minimum number of active threads
> + that can be in the thread-pool.
> +
> + - Submit work:
> + submit_threadletwork_to_queue(&myQueue, &my_work);
> +
> + - Cancel work:
> + cancel_threadletwork_on_queue(&myQueue, &my_work);
> diff --git a/qemu-threadlets.c b/qemu-threadlets.c
> new file mode 100644
> index 0000000..8fc3be0
> --- /dev/null
> +++ b/qemu-threadlets.c
> @@ -0,0 +1,167 @@
> +/*
> + * Threadlet support for offloading tasks to be executed asynchronously
> + *
> + * Copyright IBM, Corp. 2008
> + * Copyright IBM, Corp. 2010
> + *
> + * Authors:
> + * Anthony Liguori <aliguori@us.ibm.com>
> + * Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> + * Gautham R Shenoy <gautham.shenoy@gmail.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2. See
> + * the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu-threadlets.h"
> +#include "osdep.h"
> +
> +#define MAX_GLOBAL_THREADS 64
> +#define MIN_GLOBAL_THREADS 64
> +static ThreadletQueue globalqueue;
> +static int globalqueue_init;
> +
> +static void *threadlet_worker(void *data)
> +{
> + ThreadletQueue *queue = data;
> +
> + qemu_mutex_lock(&(queue->lock));
> + while (1) {
> + ThreadletWork *work;
> + int ret = 0;
> +
> + while (QTAILQ_EMPTY(&(queue->request_list)) &&
> + (ret != ETIMEDOUT)) {
> + /* wait for cond to be signalled or broadcast for 1000s */
> + ret = qemu_cond_timedwait(&(queue->cond),
> + &(queue->lock), 10*100000);
> + }
> +
> + assert(queue->idle_threads != 0);
> + if (QTAILQ_EMPTY(&(queue->request_list))) {
> + if (queue->cur_threads > queue->min_threads) {
> + /* We retain the minimum number of threads */
> + break;
> + }
> + } else {
> + work = QTAILQ_FIRST(&(queue->request_list));
> + QTAILQ_REMOVE(&(queue->request_list), work, node);
> +
> + queue->idle_threads--;
> + qemu_mutex_unlock(&(queue->lock));
> +
> + /* execute the work function */
> + work->func(work);
> +
> + qemu_mutex_lock(&(queue->lock));
> + queue->idle_threads++;
> + }
> + }
> +
> + queue->idle_threads--;
> + queue->cur_threads--;
> + qemu_mutex_unlock(&(queue->lock));
> +
> + return NULL;
> +}
> +
> +static void spawn_threadlet(ThreadletQueue *queue)
> +{
> + QemuThread thread;
> +
> + queue->cur_threads++;
> + queue->idle_threads++;
> +
> + qemu_thread_create(&thread, threadlet_worker, queue);
> +}
> +
> +/**
> + * submit_threadletwork_to_queue: Submit a new task to a private queue to be
> + * executed asynchronously.
> + * @queue: Per-subsystem private queue to which the new task needs
> + * to be submitted.
> + * @work: Contains information about the task that needs to be submitted.
> + */
> +void submit_threadletwork_to_queue(ThreadletQueue *queue, ThreadletWork *work)
> +{
> + qemu_mutex_lock(&(queue->lock));
> + if (queue->idle_threads == 0 && queue->cur_threads < queue->max_threads) {
> + spawn_threadlet(queue);
> + } else {
> + qemu_cond_signal(&(queue->cond));
> + }
> + QTAILQ_INSERT_TAIL(&(queue->request_list), work, node);
> + qemu_mutex_unlock(&(queue->lock));
> +}
> +
> +/**
> + * submit_threadletwork: Submit to the global queue a new task to be executed
> + * asynchronously.
> + * @work: Contains information about the task that needs to be submitted.
> + */
> +void submit_threadletwork(ThreadletWork *work)
> +{
> + if (unlikely(!globalqueue_init)) {
> + threadlet_queue_init(&globalqueue, MAX_GLOBAL_THREADS,
> + MIN_GLOBAL_THREADS);
> + globalqueue_init = 1;
> + }
> +
> + submit_threadletwork_to_queue(&globalqueue, work);
> +}
> +
> +/**
> + * deque_threadletwork_on_queue: Cancel a task queued on a Queue.
> + * @queue: The queue containing the task to be cancelled.
> + * @work: Contains the information of the task that needs to be cancelled.
> + *
> + * Returns: 0 if the task is successfully cancelled.
> + * 1 otherwise.
> + */
> +int deque_threadletwork_on_queue(ThreadletQueue *queue, ThreadletWork *work)
> +{
> + ThreadletWork *ret_work;
> + int ret = 1;
> +
> + qemu_mutex_lock(&(queue->lock));
> + QTAILQ_FOREACH(ret_work, &(queue->request_list), node) {
> + if (ret_work == work) {
> + QTAILQ_REMOVE(&(queue->request_list), ret_work, node);
> + ret = 0;
> + break;
> + }
> + }
> + qemu_mutex_unlock(&(queue->lock));
> +
> + return ret;
> +}
> +
> +/**
> + * deque_threadletwork: Cancel a task queued on the global queue.
> + * @work: Contains the information of the task that needs to be cancelled.
> + *
> + * Returns: 0 if the task is successfully cancelled.
> + * 1 otherwise.
> + */
> +int deque_threadletwork(ThreadletWork *work)
> +{
> + return deque_threadletwork_on_queue(&globalqueue, work);
> +}
> +
> +/**
> + * threadlet_queue_init: Initialize a threadlet queue.
> + * @queue: The threadlet queue to be initialized.
> + * @max_threads: Maximum number of threads processing the queue.
> + * @min_threads: Minimum number of threads processing the queue.
> + */
> +void threadlet_queue_init(ThreadletQueue *queue,
> + int max_threads, int min_threads)
> +{
> + queue->cur_threads = 0;
> + queue->idle_threads = 0;
> + queue->max_threads = max_threads;
> + queue->min_threads = min_threads;
> + QTAILQ_INIT(&(queue->request_list));
> + qemu_mutex_init(&(queue->lock));
> + qemu_cond_init(&(queue->cond));
> +}
> diff --git a/qemu-threadlets.h b/qemu-threadlets.h
> new file mode 100644
> index 0000000..6d9585b
> --- /dev/null
> +++ b/qemu-threadlets.h
> @@ -0,0 +1,48 @@
> +/*
> + * Threadlet support for offloading tasks to be executed asynchronously
> + *
> + * Copyright IBM, Corp. 2008
> + * Copyright IBM, Corp. 2010
> + *
> + * Authors:
> + * Anthony Liguori <aliguori@us.ibm.com>
> + * Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> + * Gautham R Shenoy <ego@in.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2. See
> + * the COPYING file in the top-level directory.
> + */
> +
> +#ifndef QEMU_ASYNC_WORK_H
> +#define QEMU_ASYNC_WORK_H
> +
> +#include "qemu-queue.h"
> +#include "qemu-common.h"
> +#include "qemu-thread.h"
> +
> +typedef struct ThreadletQueue
> +{
> + QemuMutex lock;
> + QemuCond cond;
> + int max_threads;
> + int min_threads;
> + int cur_threads;
> + int idle_threads;
> + QTAILQ_HEAD(, ThreadletWork) request_list;
> +} ThreadletQueue;
> +
> +typedef struct ThreadletWork
> +{
> + QTAILQ_ENTRY(ThreadletWork) node;
> + void (*func)(struct ThreadletWork *work);
> +} ThreadletWork;
> +
> +extern void submit_threadletwork_to_queue(ThreadletQueue *queue,
> + ThreadletWork *work);
> +extern void submit_threadletwork(ThreadletWork *work);
> +extern int deque_threadletwork_on_queue(ThreadletQueue *queue,
> + ThreadletWork *work);
> +extern int deque_threadletwork(ThreadletWork *work);
> +extern void threadlet_queue_init(ThreadletQueue *queue, int max_threads,
> + int min_threads);
'extern' is not useful for function prototypes.
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [Qemu-devel] [PATCH 1/3] Introduce threadlets
2010-10-26 14:14 ` [Qemu-devel] [PATCH 1/3] Introduce threadlets Arun R Bharadwaj
2010-10-26 19:31 ` Blue Swirl
@ 2010-11-01 13:40 ` Anthony Liguori
2010-11-05 6:48 ` Arun R Bharadwaj
1 sibling, 1 reply; 8+ messages in thread
From: Anthony Liguori @ 2010-11-01 13:40 UTC (permalink / raw)
To: Arun R Bharadwaj; +Cc: qemu-devel
On 10/26/2010 09:14 AM, Arun R Bharadwaj wrote:
> From: Aneesh Kumar K.V<aneesh.kumar@linux.vnet.ibm.com>
>
> This patch creates a generic asynchronous-task-offloading infrastructure named
> threadlets. The core idea has been borrowed from the threading framework that
> is being used by paio.
>
> The reason for creating this generic infrastructure is so that other subsystems,
> such as virtio-9p could make use of it for offloading tasks that could block.
>
> The patch creates a global queue on-to which subsystems can queue their tasks to
> be executed asynchronously.
>
> The patch also provides API's that allow a subsystem to create a private queue
> with an associated pool of threads.
>
> [ego@in.ibm.com: Facelift of the code, Documentation, cancel_threadlet
> and other helpers]
>
> Signed-off-by: Aneesh Kumar K.V<aneesh.kumar@linux.vnet.ibm.com>
> Signed-off-by: Gautham R Shenoy<gautham.shenoy@gmail.com>
> Signed-off-by: Sripathi Kodi<sripathik@in.ibm.com>
> Signed-off-by: Arun R Bharadwaj<arun@linux.vnet.ibm.com>
> ---
> Makefile.objs | 3 +
> docs/async-support.txt | 141 +++++++++++++++++++++++++++++++++++++++++
> qemu-threadlets.c | 167 ++++++++++++++++++++++++++++++++++++++++++++++++
> qemu-threadlets.h | 48 ++++++++++++++
> 4 files changed, 358 insertions(+), 1 deletions(-)
> create mode 100644 docs/async-support.txt
> create mode 100644 qemu-threadlets.c
> create mode 100644 qemu-threadlets.h
>
> diff --git a/Makefile.objs b/Makefile.objs
> index cd5a24b..2cf8aba 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -9,6 +9,8 @@ qobject-obj-y += qerror.o
>
> block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
> block-obj-y += nbd.o block.o aio.o aes.o osdep.o qemu-config.o
> +block-obj-$(CONFIG_POSIX) += qemu-thread.o
> +block-obj-$(CONFIG_POSIX) += qemu-threadlets.o
> block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
> block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
>
> @@ -124,7 +126,6 @@ endif
> common-obj-y += $(addprefix ui/, $(ui-obj-y))
>
> common-obj-y += iov.o acl.o
> -common-obj-$(CONFIG_THREAD) += qemu-thread.o
> common-obj-y += notify.o event_notifier.o
> common-obj-y += qemu-timer.o
>
> diff --git a/docs/async-support.txt b/docs/async-support.txt
> new file mode 100644
> index 0000000..9f22b9a
> --- /dev/null
> +++ b/docs/async-support.txt
> @@ -0,0 +1,141 @@
> +== How to use the threadlets infrastructure supported in Qemu ==
> +
> +== Threadlets ==
> +
> +Q.1: What are threadlets ?
> +A.1: Threadlets is an infrastructure within QEMU that allows other subsystems
> + to offload possibly blocking work to a queue to be processed by a pool
> + of threads asynchronously.
> +
> +Q.2: When would one want to use threadlets ?
> +A.2: Threadlets are useful when there are operations that can be performed
> + outside the context of the VCPU/IO threads inorder to free these latter
> + to service any other guest requests.
> +
> +Q.3: I have some work that can be executed in an asynchronous context. How
> + should I go about it ?
> +A.3: One could follow the steps listed below:
> +
> + - Define a function which would do the asynchronous work.
> + static void my_threadlet_func(ThreadletWork *work)
> + {
> + }
> +
> + - Declare an object of type ThreadletWork;
> + ThreadletWork work;
> +
> +
> + - Assign a value to the "func" member of ThreadletWork object.
> + work.func = my_threadlet_func;
> +
> + - Submit the threadlet to the global queue.
> + submit_threadletwork(&work);
> +
> + - Continue servicing some other guest operations.
> +
> +Q.4: I want to my_threadlet_func to access some non-global data. How do I do
> + that ?
> +A.4: Suppose you want my_threadlet_func to access some non-global data-object
> + of type myPrivateData. In that case one could follow the following steps.
> +
> + - Define a member of the type ThreadletWork within myPrivateData.
> + typedef struct MyPrivateData {
> + ...;
> + ...;
> + ...;
> + ThreadletWork work;
> + } MyPrivateData;
> +
> + MyPrivateData my_data;
> +
> + - Initialize myData.work as described in A.3
> + myData.work.func = my_threadlet_func;
> + submit_threadletwork(&myData.work);
> +
> + - Access the myData object inside my_threadlet_func() using container_of
> + primitive
> + static void my_threadlet_func(ThreadletWork *work)
> + {
> + myPrivateData *mydata_ptr;
> + mydata_ptr = container_of(work, myPrivateData, work);
> +
> + /* mydata_ptr now points to myData object */
> + }
> +
> +Q.5: Are there any precautions one must take while sharing data with the
> + Asynchronous thread-pool ?
> +A.5: Yes, make sure that the helper function of the type my_threadlet_func()
> + does not access/modify data when it can be accessed or modified in the
> + context of VCPU thread or IO thread. This is because the asynchronous
> + threads in the pool can run in parallel with the VCPU/IOThreads as shown
> + in the figure.
> +
> + A typical workflow is as follows:
> +
> + VCPU/IOThread
> + |
> + | (1)
> + |
> + V
> + Offload work (2)
> + |-------> to threadlets -----------------------------> Helper thread
> + | | |
> + | | |
> + | | (3) | (4)
> + | | |
> + | Handle other Guest requests |
> + | | |
> + | | V
> + | | (3) Signal the I/O Thread
> + |(6) | |
> + | | /
> + | | /
> + | V /
> + | Do the post<---------------------------------/
> + | processing (5)
> + | |
> + | | (6)
> + | V
> + |-Yes------ More async work?
> + |
> + | (7)
> + No
> + |
> + |
> + .
> + .
> +
> + Hence one needs to make sure that in the steps (3) and (4) which run in
> + parallel, any global data is accessed within only one context.
> +
> +Q.6: I have queued a threadlet which I want to cancel. How do I do that ?
> +A.6: Threadlets framework provides the API cancel_threadlet:
> + - int cancel_threadletwork(ThreadletWork *work)
> +
> + The API scans the ThreadletQueue to see if (work) is present. If it finds
> + work, it'll dequeue work and return 0.
> +
> + On the other hand, if it does not find the (work) in the ThreadletQueue,
> + then it'll return 1. This can imply two things. Either the work is being
> + processed by one of the helper threads or it has been processed. The
> + threadlet infrastructure currently _does_not_ distinguish between these
> + two and the onus is on the caller to do that.
> +
> +Q.7: Apart from the global pool of threads, can I have my own private Queue ?
> +A.7: Yes, the threadlets framework allows subsystems to create their own private
> + queues with associated pools of threads.
> +
> + - Define a PrivateQueue
> + ThreadletQueue myQueue;
> +
> + - Initialize it:
> + threadlet_queue_init(&myQueue, my_max_threads, my_min_threads);
> + where my_max_threads is the maximum number of threads that can be in the
> + thread pool and my_min_threads is the minimum number of active threads
> + that can be in the thread-pool.
> +
> + - Submit work:
> + submit_threadletwork_to_queue(&myQueue,&my_work);
> +
> + - Cancel work:
> + cancel_threadletwork_on_queue(&myQueue,&my_work);
> diff --git a/qemu-threadlets.c b/qemu-threadlets.c
> new file mode 100644
> index 0000000..8fc3be0
> --- /dev/null
> +++ b/qemu-threadlets.c
> @@ -0,0 +1,167 @@
> +/*
> + * Threadlet support for offloading tasks to be executed asynchronously
> + *
> + * Copyright IBM, Corp. 2008
> + * Copyright IBM, Corp. 2010
> + *
> + * Authors:
> + * Anthony Liguori<aliguori@us.ibm.com>
> + * Aneesh Kumar K.V<aneesh.kumar@linux.vnet.ibm.com>
> + * Gautham R Shenoy<gautham.shenoy@gmail.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2. See
> + * the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu-threadlets.h"
> +#include "osdep.h"
> +
> +#define MAX_GLOBAL_THREADS 64
> +#define MIN_GLOBAL_THREADS 64
> +static ThreadletQueue globalqueue;
> +static int globalqueue_init;
> +
> +static void *threadlet_worker(void *data)
> +{
> + ThreadletQueue *queue = data;
> +
> + qemu_mutex_lock(&(queue->lock));
>
The use of parens here is unnecessary and unusual within the code base.
I'd prefer that they be dropped.
> + while (1) {
> + ThreadletWork *work;
> + int ret = 0;
> +
> + while (QTAILQ_EMPTY(&(queue->request_list))&&
> + (ret != ETIMEDOUT)) {
> + /* wait for cond to be signalled or broadcast for 1000s */
> + ret = qemu_cond_timedwait(&(queue->cond),
> + &(queue->lock), 10*100000);
> + }
> +
> + assert(queue->idle_threads != 0);
> + if (QTAILQ_EMPTY(&(queue->request_list))) {
> + if (queue->cur_threads> queue->min_threads) {
> + /* We retain the minimum number of threads */
> + break;
>
You set MIN_GLOBAL_THREADS to MAX_GLOBAL_THREADS which makes this dead
code. Why are you forcing the thread pool to remain a fixed size?+/**
> + * submit_threadletwork: Submit to the global queue a new task to be executed
> + * asynchronously.
> + * @work: Contains information about the task that needs to be submitted.
> + */
> +void submit_threadletwork(ThreadletWork *work)
> +{
> + if (unlikely(!globalqueue_init)) {
>
Why have this unlikely?
> +/**
> + * deque_threadletwork: Cancel a task queued on the global queue.
> + * @work: Contains the information of the task that needs to be cancelled.
> + *
> + * Returns: 0 if the task is successfully cancelled.
> + * 1 otherwise.
> + */
> +int deque_threadletwork(ThreadletWork *work)
> +{
> + return deque_threadletwork_on_queue(&globalqueue, work);
> +}
>
I really struggle with the use of namespaces here.
Wouldn't threadletwork_deque make more sense? And I think dequeue is
the proper spelling.
threadletwork is too long of a name too.
> +/**
> + * threadlet_queue_init: Initialize a threadlet queue.
> + * @queue: The threadlet queue to be initialized.
> + * @max_threads: Maximum number of threads processing the queue.
> + * @min_threads: Minimum number of threads processing the queue.
> + */
> +void threadlet_queue_init(ThreadletQueue *queue,
> + int max_threads, int min_threads)
> +{
> + queue->cur_threads = 0;
> + queue->idle_threads = 0;
> + queue->max_threads = max_threads;
> + queue->min_threads = min_threads;
> + QTAILQ_INIT(&(queue->request_list));
> + qemu_mutex_init(&(queue->lock));
> + qemu_cond_init(&(queue->cond));
> +}
>
It's unclear to me why we need to have multiple threadlet pools. Why
not just have a single global threadlet pool?
Regards,
Anthony Liguori
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [Qemu-devel] [PATCH 1/3] Introduce threadlets
2010-11-01 13:40 ` Anthony Liguori
@ 2010-11-05 6:48 ` Arun R Bharadwaj
0 siblings, 0 replies; 8+ messages in thread
From: Arun R Bharadwaj @ 2010-11-05 6:48 UTC (permalink / raw)
To: Anthony Liguori; +Cc: qemu-devel
* Anthony Liguori <anthony@codemonkey.ws> [2010-11-01 08:40:36]:
> On 10/26/2010 09:14 AM, Arun R Bharadwaj wrote:
> >+Q.7: Apart from the global pool of threads, can I have my own private Queue ?
> >+A.7: Yes, the threadlets framework allows subsystems to create their own private
> >+ queues with associated pools of threads.
> >+
> >+ - Define a PrivateQueue
> >+ ThreadletQueue myQueue;
> >+
> >+ - Initialize it:
> >+ threadlet_queue_init(&myQueue, my_max_threads, my_min_threads);
> >+ where my_max_threads is the maximum number of threads that can be in the
> >+ thread pool and my_min_threads is the minimum number of active threads
> >+ that can be in the thread-pool.
> >+
> >+ - Submit work:
> >+ submit_threadletwork_to_queue(&myQueue,&my_work);
> >+
> >+ - Cancel work:
> >+ cancel_threadletwork_on_queue(&myQueue,&my_work);
> >diff --git a/qemu-threadlets.c b/qemu-threadlets.c
> >new file mode 100644
> >index 0000000..8fc3be0
> >--- /dev/null
> >+++ b/qemu-threadlets.c
> >@@ -0,0 +1,167 @@
> >+/*
> >+ * Threadlet support for offloading tasks to be executed asynchronously
> >+ *
> >+ * Copyright IBM, Corp. 2008
> >+ * Copyright IBM, Corp. 2010
> >+ *
> >+ * Authors:
> >+ * Anthony Liguori<aliguori@us.ibm.com>
> >+ * Aneesh Kumar K.V<aneesh.kumar@linux.vnet.ibm.com>
> >+ * Gautham R Shenoy<gautham.shenoy@gmail.com>
> >+ *
> >+ * This work is licensed under the terms of the GNU GPL, version 2. See
> >+ * the COPYING file in the top-level directory.
> >+ */
> >+
> >+#include "qemu-threadlets.h"
> >+#include "osdep.h"
> >+
> >+#define MAX_GLOBAL_THREADS 64
> >+#define MIN_GLOBAL_THREADS 64
> >+static ThreadletQueue globalqueue;
> >+static int globalqueue_init;
> >+
> >+static void *threadlet_worker(void *data)
> >+{
> >+ ThreadletQueue *queue = data;
> >+
> >+ qemu_mutex_lock(&(queue->lock));
>
> The use of parens here is unnecessary and unusual within the code
> base. I'd prefer that they be dropped.
>
> >+ while (1) {
> >+ ThreadletWork *work;
> >+ int ret = 0;
> >+
> >+ while (QTAILQ_EMPTY(&(queue->request_list))&&
> >+ (ret != ETIMEDOUT)) {
> >+ /* wait for cond to be signalled or broadcast for 1000s */
> >+ ret = qemu_cond_timedwait(&(queue->cond),
> >+ &(queue->lock), 10*100000);
> >+ }
> >+
> >+ assert(queue->idle_threads != 0);
> >+ if (QTAILQ_EMPTY(&(queue->request_list))) {
> >+ if (queue->cur_threads> queue->min_threads) {
> >+ /* We retain the minimum number of threads */
> >+ break;
>
> You set MIN_GLOBAL_THREADS to MAX_GLOBAL_THREADS which makes this
> dead code. Why are you forcing the thread pool to remain a fixed
> size?+/**
>
> >+ * submit_threadletwork: Submit to the global queue a new task to be executed
> >+ * asynchronously.
> >+ * @work: Contains information about the task that needs to be submitted.
> >+ */
> >+void submit_threadletwork(ThreadletWork *work)
> >+{
> >+ if (unlikely(!globalqueue_init)) {
>
> Why have this unlikely?
>
> >+/**
> >+ * deque_threadletwork: Cancel a task queued on the global queue.
> >+ * @work: Contains the information of the task that needs to be cancelled.
> >+ *
> >+ * Returns: 0 if the task is successfully cancelled.
> >+ * 1 otherwise.
> >+ */
> >+int deque_threadletwork(ThreadletWork *work)
> >+{
> >+ return deque_threadletwork_on_queue(&globalqueue, work);
> >+}
>
> I really struggle with the use of namespaces here.
>
> Wouldn't threadletwork_deque make more sense? And I think dequeue
> is the proper spelling.
>
> threadletwork is too long of a name too.
>
> >+/**
> >+ * threadlet_queue_init: Initialize a threadlet queue.
> >+ * @queue: The threadlet queue to be initialized.
> >+ * @max_threads: Maximum number of threads processing the queue.
> >+ * @min_threads: Minimum number of threads processing the queue.
> >+ */
> >+void threadlet_queue_init(ThreadletQueue *queue,
> >+ int max_threads, int min_threads)
> >+{
> >+ queue->cur_threads = 0;
> >+ queue->idle_threads = 0;
> >+ queue->max_threads = max_threads;
> >+ queue->min_threads = min_threads;
> >+ QTAILQ_INIT(&(queue->request_list));
> >+ qemu_mutex_init(&(queue->lock));
> >+ qemu_cond_init(&(queue->cond));
> >+}
>
> It's unclear to me why we need to have multiple threadlet pools.
> Why not just have a single global threadlet pool?
>
According to Gautham's original patchset, there is a global threadlet
pool and also a private threadlet pool which any subsystem can
declare. I have just retained the same design. This is described in
the documentation file.
-arun
> Regards,
>
> Anthony Liguori
>
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Qemu-devel] [PATCH 2/3] Make paio subsystem use threadlets
2010-10-26 14:14 [Qemu-devel] v8: [PATCH 0/3] Threadlets: A generic task offloading framework Arun R Bharadwaj
2010-10-26 14:14 ` [Qemu-devel] [PATCH 1/3] Introduce threadlets Arun R Bharadwaj
@ 2010-10-26 14:14 ` Arun R Bharadwaj
2010-10-27 9:17 ` Stefan Hajnoczi
2010-10-26 14:14 ` [Qemu-devel] [PATCH 3/3] Add helper functions to enable virtio-9p make use of the threadlets Arun R Bharadwaj
2 siblings, 1 reply; 8+ messages in thread
From: Arun R Bharadwaj @ 2010-10-26 14:14 UTC (permalink / raw)
To: qemu-devel
From: Gautham R Shenoy <ego@in.ibm.com>
This patch makes the paio subsystem use the threadlet framework thereby
decoupling asynchronous threading framework portion out of
posix-aio-compat.c
The patch has been tested with fstress.
Signed-off-by: Gautham R Shenoy <gautham.shenoy@gmail.com>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
---
posix-aio-compat.c | 170 ++++++++++------------------------------------------
1 files changed, 33 insertions(+), 137 deletions(-)
diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 7b862b5..2e47736 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -29,6 +29,7 @@
#include "block_int.h"
#include "block/raw-posix-aio.h"
+#include "qemu-threadlets.h"
struct qemu_paiocb {
@@ -44,13 +45,13 @@ struct qemu_paiocb {
int ev_signo;
off_t aio_offset;
- QTAILQ_ENTRY(qemu_paiocb) node;
int aio_type;
ssize_t ret;
int active;
struct qemu_paiocb *next;
int async_context_id;
+ ThreadletWork work;
};
typedef struct PosixAioState {
@@ -59,15 +60,6 @@ typedef struct PosixAioState {
} PosixAioState;
-static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
-static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
-static pthread_t thread_id;
-static pthread_attr_t attr;
-static int max_threads = 64;
-static int cur_threads = 0;
-static int idle_threads = 0;
-static QTAILQ_HEAD(, qemu_paiocb) request_list;
-
#ifdef CONFIG_PREADV
static int preadv_present = 1;
#else
@@ -85,39 +77,6 @@ static void die(const char *what)
die2(errno, what);
}
-static void mutex_lock(pthread_mutex_t *mutex)
-{
- int ret = pthread_mutex_lock(mutex);
- if (ret) die2(ret, "pthread_mutex_lock");
-}
-
-static void mutex_unlock(pthread_mutex_t *mutex)
-{
- int ret = pthread_mutex_unlock(mutex);
- if (ret) die2(ret, "pthread_mutex_unlock");
-}
-
-static int cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
- struct timespec *ts)
-{
- int ret = pthread_cond_timedwait(cond, mutex, ts);
- if (ret && ret != ETIMEDOUT) die2(ret, "pthread_cond_timedwait");
- return ret;
-}
-
-static void cond_signal(pthread_cond_t *cond)
-{
- int ret = pthread_cond_signal(cond);
- if (ret) die2(ret, "pthread_cond_signal");
-}
-
-static void thread_create(pthread_t *thread, pthread_attr_t *attr,
- void *(*start_routine)(void*), void *arg)
-{
- int ret = pthread_create(thread, attr, start_routine, arg);
- if (ret) die2(ret, "pthread_create");
-}
-
static ssize_t handle_aiocb_ioctl(struct qemu_paiocb *aiocb)
{
int ret;
@@ -301,106 +260,53 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
return nbytes;
}
-static void *aio_thread(void *unused)
+static void aio_thread(ThreadletWork *work)
{
pid_t pid;
+ struct qemu_paiocb *aiocb = container_of(work, struct qemu_paiocb, work);
+ ssize_t ret = 0;
pid = getpid();
+ aiocb->active = 1;
- while (1) {
- struct qemu_paiocb *aiocb;
- ssize_t ret = 0;
- qemu_timeval tv;
- struct timespec ts;
-
- qemu_gettimeofday(&tv);
- ts.tv_sec = tv.tv_sec + 10;
- ts.tv_nsec = 0;
-
- mutex_lock(&lock);
-
- while (QTAILQ_EMPTY(&request_list) &&
- !(ret == ETIMEDOUT)) {
- ret = cond_timedwait(&cond, &lock, &ts);
- }
-
- if (QTAILQ_EMPTY(&request_list))
- break;
-
- aiocb = QTAILQ_FIRST(&request_list);
- QTAILQ_REMOVE(&request_list, aiocb, node);
- aiocb->active = 1;
- idle_threads--;
- mutex_unlock(&lock);
-
- switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
- case QEMU_AIO_READ:
- case QEMU_AIO_WRITE:
- ret = handle_aiocb_rw(aiocb);
- break;
- case QEMU_AIO_FLUSH:
- ret = handle_aiocb_flush(aiocb);
- break;
- case QEMU_AIO_IOCTL:
- ret = handle_aiocb_ioctl(aiocb);
- break;
- default:
- fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
- ret = -EINVAL;
- break;
- }
-
- mutex_lock(&lock);
- aiocb->ret = ret;
- idle_threads++;
- mutex_unlock(&lock);
-
- if (kill(pid, aiocb->ev_signo)) die("kill failed");
+ switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
+ case QEMU_AIO_READ:
+ case QEMU_AIO_WRITE:
+ ret = handle_aiocb_rw(aiocb);
+ break;
+ case QEMU_AIO_FLUSH:
+ ret = handle_aiocb_flush(aiocb);
+ break;
+ case QEMU_AIO_IOCTL:
+ ret = handle_aiocb_ioctl(aiocb);
+ break;
+ default:
+ fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
+ ret = -EINVAL;
+ break;
}
- idle_threads--;
- cur_threads--;
- mutex_unlock(&lock);
-
- return NULL;
-}
+ aiocb->ret = ret;
-static void spawn_thread(void)
-{
- sigset_t set, oldset;
-
- cur_threads++;
- idle_threads++;
-
- /* block all signals */
- if (sigfillset(&set)) die("sigfillset");
- if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");
-
- thread_create(&thread_id, &attr, aio_thread, NULL);
-
- if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
+ if (kill(pid, aiocb->ev_signo)) {
+ die("kill failed");
+ }
}
static void qemu_paio_submit(struct qemu_paiocb *aiocb)
{
aiocb->ret = -EINPROGRESS;
aiocb->active = 0;
- mutex_lock(&lock);
- if (idle_threads == 0 && cur_threads < max_threads)
- spawn_thread();
- QTAILQ_INSERT_TAIL(&request_list, aiocb, node);
- mutex_unlock(&lock);
- cond_signal(&cond);
+
+ aiocb->work.func = aio_thread;
+ submit_threadletwork(&aiocb->work);
}
static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)
{
ssize_t ret;
- mutex_lock(&lock);
ret = aiocb->ret;
- mutex_unlock(&lock);
-
return ret;
}
@@ -536,14 +442,15 @@ static void paio_cancel(BlockDriverAIOCB *blockacb)
struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
int active = 0;
- mutex_lock(&lock);
if (!acb->active) {
- QTAILQ_REMOVE(&request_list, acb, node);
- acb->ret = -ECANCELED;
+ if (!deque_threadletwork(&acb->work)) {
+ acb->ret = -ECANCELED;
+ } else {
+ active = 1;
+ }
} else if (acb->ret == -EINPROGRESS) {
active = 1;
}
- mutex_unlock(&lock);
if (active) {
/* fail safe: if the aio could not be canceled, we wait for
@@ -618,7 +525,6 @@ int paio_init(void)
struct sigaction act;
PosixAioState *s;
int fds[2];
- int ret;
if (posix_aio_state)
return 0;
@@ -645,16 +551,6 @@ int paio_init(void)
qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush,
posix_aio_process_queue, s);
- ret = pthread_attr_init(&attr);
- if (ret)
- die2(ret, "pthread_attr_init");
-
- ret = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
- if (ret)
- die2(ret, "pthread_attr_setdetachstate");
-
- QTAILQ_INIT(&request_list);
-
posix_aio_state = s;
return 0;
}
^ permalink raw reply related [flat|nested] 8+ messages in thread* [Qemu-devel] [PATCH 3/3] Add helper functions to enable virtio-9p make use of the threadlets
2010-10-26 14:14 [Qemu-devel] v8: [PATCH 0/3] Threadlets: A generic task offloading framework Arun R Bharadwaj
2010-10-26 14:14 ` [Qemu-devel] [PATCH 1/3] Introduce threadlets Arun R Bharadwaj
2010-10-26 14:14 ` [Qemu-devel] [PATCH 2/3] Make paio subsystem use threadlets Arun R Bharadwaj
@ 2010-10-26 14:14 ` Arun R Bharadwaj
2 siblings, 0 replies; 8+ messages in thread
From: Arun R Bharadwaj @ 2010-10-26 14:14 UTC (permalink / raw)
To: qemu-devel
From: Gautham R Shenoy <ego@in.ibm.com>
infrastructure for offloading blocking tasks such as making posix calls on
to the helper threads and handle the post_posix_operations() from the
context of the iothread. This frees the vcpu thread to process any other guest
operations while the processing of v9fs_io is in progress.
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
---
hw/virtio-9p.c | 164 ++++++++++++++++++++++++++++++++++++++++++++++++++++
posix-aio-compat.c | 46 +++++----------
qemu-threadlets.c | 21 +++++++
qemu-threadlets.h | 1
vl.c | 3 +
5 files changed, 205 insertions(+), 30 deletions(-)
diff --git a/hw/virtio-9p.c b/hw/virtio-9p.c
index a871685..cc8b860 100644
--- a/hw/virtio-9p.c
+++ b/hw/virtio-9p.c
@@ -18,6 +18,7 @@
#include "fsdev/qemu-fsdev.h"
#include "virtio-9p-debug.h"
#include "virtio-9p-xattr.h"
+#include "qemu-threadlets.h"
int debug_9p_pdu;
@@ -33,6 +34,149 @@ enum {
Oappend = 0x80,
};
+struct v9fs_post_op {
+ QTAILQ_ENTRY(v9fs_post_op) node;
+ void (*func)(void *arg);
+ void *arg;
+};
+
+static struct {
+ int rfd;
+ int wfd;
+ QemuMutex lock;
+ QTAILQ_HEAD(, v9fs_post_op) post_op_list;
+} v9fs_async_struct;
+
+static void die2(int err, const char *what)
+{
+ fprintf(stderr, "%s failed: %s\n", what, strerror(err));
+ abort();
+}
+
+static void die(const char *what)
+{
+ die2(errno, what);
+}
+
+#define ASYNC_MAX_PROCESS 5
+
+/**
+ * v9fs_process_post_ops: Process any pending v9fs_post_posix_operation
+ * @arg: Not used.
+ *
+ * This function serves as a callback to the iothread to be called into whenever
+ * the v9fs_async_struct.wfd is written into. This thread goes through the list
+ * of v9fs_post_posix_operations() and executes them. In the process, it might
+ * queue more job on the asynchronous thread pool.
+ */
+static void v9fs_process_post_ops(void *arg)
+{
+ int count = 0;
+ struct v9fs_post_op *post_op;
+ int ret;
+ char byte;
+
+ qemu_mutex_lock(&v9fs_async_struct.lock);
+ do {
+ ret = read(v9fs_async_struct.rfd, &byte, sizeof(byte));
+ } while (ret >= 0 || errno != EAGAIN);
+
+ for (count = 0; count < ASYNC_MAX_PROCESS; count++) {
+ if (QTAILQ_EMPTY(&(v9fs_async_struct.post_op_list))) {
+ break;
+ }
+ post_op = QTAILQ_FIRST(&(v9fs_async_struct.post_op_list));
+ QTAILQ_REMOVE(&(v9fs_async_struct.post_op_list), post_op, node);
+
+ qemu_mutex_unlock(&v9fs_async_struct.lock);
+ post_op->func(post_op->arg);
+ qemu_free(post_op);
+ qemu_mutex_lock(&v9fs_async_struct.lock);
+ }
+ qemu_mutex_unlock(&v9fs_async_struct.lock);
+}
+
+/**
+ * v9fs_async_signal: Inform the io-thread of completion of async job.
+ *
+ * This function is used to inform the iothread that a particular
+ * async-operation pertaining to v9fs has been completed and that the io thread
+ * can handle the v9fs_post_posix_operation.
+ *
+ * This is based on the aio_signal_handler
+ */
+static inline void v9fs_async_signal(void)
+{
+ char byte = 0;
+ ssize_t ret;
+ int tries = 0;
+
+ qemu_mutex_lock(&v9fs_async_struct.lock);
+ do {
+ assert(tries != 100);
+ ret = write(v9fs_async_struct.wfd, &byte, sizeof(byte));
+ tries++;
+ } while (ret < 0 && errno == EAGAIN);
+ qemu_mutex_unlock(&v9fs_async_struct.lock);
+
+ if (ret < 0 && errno != EAGAIN) {
+ die("write() in v9fs");
+ }
+
+ if (kill(getpid(), SIGUSR2)) {
+ die("kill failed");
+ }
+}
+
+/**
+ * v9fs_async_helper_done: Marks the completion of the v9fs_async job
+ * @func: v9fs_post_posix_func() for post-processing invoked in the context of
+ * the io-thread
+ * @arg: Argument to func.
+ *
+ * This function is called from the context of one of the asynchronous threads
+ * in the thread pool. This is called when the asynchronous thread has finished
+ * executing a v9fs_posix_operation. It's purpose is to initiate the process of
+ * informing the io-thread that the v9fs_posix_operation has completed.
+ */
+static void v9fs_async_helper_done(void (*func)(void *arg), void *arg)
+{
+ struct v9fs_post_op *post_op;
+
+ post_op = qemu_mallocz(sizeof(*post_op));
+ post_op->func = func;
+ post_op->arg = arg;
+
+ qemu_mutex_lock(&v9fs_async_struct.lock);
+ QTAILQ_INSERT_TAIL(&(v9fs_async_struct.post_op_list), post_op, node);
+ qemu_mutex_unlock(&v9fs_async_struct.lock);
+
+ v9fs_async_signal();
+}
+
+/**
+ * v9fs_do_async_posix: Offload v9fs_posix_operation onto async thread.
+ * @vs: V9fsOPState variable for the OP operation.
+ * @posix_fn: The posix function which has to be offloaded onto async thread.
+ * @post_fn_ptr: Address of the location to hold the post_fn corresponding to
+ * the posix_fn
+ * @post_fn: The post processing function corresponding to the posix_fn.
+ *
+ * This function is a helper to offload posix_operation on to the asynchronous
+ * thread pool. It sets up the associations with the post_function that needs to
+ * be invoked by from the context of the iothread once the posix_fn has been
+ * executed.
+ */
+static void v9fs_do_async_posix(ThreadletWork *work ,
+ void (*posix_fn)(ThreadletWork *work),
+ void (**post_fn_ptr)(void *arg),
+ void (*post_fn)(void *arg))
+{
+ *post_fn_ptr = post_fn;
+ work->func = posix_fn;
+ submit_threadletwork(work);
+}
+
static int omode_to_uflags(int8_t mode)
{
int ret = 0;
@@ -3639,7 +3783,7 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
int i, len;
struct stat stat;
FsTypeEntry *fse;
-
+ int fds[2];
s = (V9fsState *)virtio_common_init("virtio-9p",
VIRTIO_ID_9P,
@@ -3722,5 +3866,23 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
s->tag_len;
s->vdev.get_config = virtio_9p_get_config;
+ if (qemu_pipe(fds) == -1) {
+ fprintf(stderr, "failed to create fd's for virtio-9p\n");
+ exit(1);
+ }
+
+ v9fs_async_struct.rfd = fds[0];
+ v9fs_async_struct.wfd = fds[1];
+
+ fcntl(fds[0], F_SETFL, O_NONBLOCK);
+ fcntl(fds[1], F_SETFL, O_NONBLOCK);
+
+ qemu_set_fd_handler(fds[0], v9fs_process_post_ops, NULL, NULL);
+ QTAILQ_INIT(&v9fs_async_struct.post_op_list);
+ qemu_mutex_init(&(v9fs_async_struct.lock));
+
+ (void)v9fs_do_async_posix;
+ (void)v9fs_async_helper_done;
+
return &s->vdev;
}
diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 2e47736..ba146c4 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -260,6 +260,8 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
return nbytes;
}
+static PosixAioState *posix_aio_state;
+
static void aio_thread(ThreadletWork *work)
{
pid_t pid;
@@ -288,6 +290,14 @@ static void aio_thread(ThreadletWork *work)
aiocb->ret = ret;
+ char byte = 0;
+ ssize_t ret;
+
+ ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
+ if (ret < 0 && errno != EAGAIN) {
+ die("write()");
+ }
+
if (kill(pid, aiocb->ev_signo)) {
die("kill failed");
}
@@ -402,22 +412,6 @@ static int posix_aio_flush(void *opaque)
return !!s->first_aio;
}
-static PosixAioState *posix_aio_state;
-
-static void aio_signal_handler(int signum)
-{
- if (posix_aio_state) {
- char byte = 0;
- ssize_t ret;
-
- ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
- if (ret < 0 && errno != EAGAIN)
- die("write()");
- }
-
- qemu_service_io();
-}
-
static void paio_remove(struct qemu_paiocb *acb)
{
struct qemu_paiocb **pacb;
@@ -442,13 +436,13 @@ static void paio_cancel(BlockDriverAIOCB *blockacb)
struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
int active = 0;
- if (!acb->active) {
- if (!deque_threadletwork(&acb->work)) {
- acb->ret = -ECANCELED;
- } else {
- active = 1;
- }
- } else if (acb->ret == -EINPROGRESS) {
+ if (!deque_threadletwork(&acb->work)) {
+ acb->ret = -ECANCELED;
+ } else {
+ active = 1;
+ }
+
+ if (acb->ret == -EINPROGRESS) {
active = 1;
}
@@ -522,7 +516,6 @@ BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
int paio_init(void)
{
- struct sigaction act;
PosixAioState *s;
int fds[2];
@@ -531,11 +524,6 @@ int paio_init(void)
s = qemu_malloc(sizeof(PosixAioState));
- sigfillset(&act.sa_mask);
- act.sa_flags = 0; /* do not restart syscalls to interrupt select() */
- act.sa_handler = aio_signal_handler;
- sigaction(SIGUSR2, &act, NULL);
-
s->first_aio = NULL;
if (qemu_pipe(fds) == -1) {
fprintf(stderr, "failed to create pipe\n");
diff --git a/qemu-threadlets.c b/qemu-threadlets.c
index 8fc3be0..7466481 100644
--- a/qemu-threadlets.c
+++ b/qemu-threadlets.c
@@ -15,12 +15,28 @@
#include "qemu-threadlets.h"
#include "osdep.h"
+#include <signal.h>
#define MAX_GLOBAL_THREADS 64
#define MIN_GLOBAL_THREADS 64
static ThreadletQueue globalqueue;
static int globalqueue_init;
+static void threadlet_io_completion_signal_handler(int signum)
+{
+ qemu_service_io();
+}
+
+static void threadlet_register_signal_handler(void)
+{
+ struct sigaction act;
+
+ sigfillset(&act.sa_mask);
+ act.sa_flags = 0; /* do not restart syscalls to interrupt select() */
+ act.sa_handler = threadlet_io_completion_signal_handler;
+ sigaction(SIGUSR2, &act, NULL);
+}
+
static void *threadlet_worker(void *data)
{
ThreadletQueue *queue = data;
@@ -165,3 +181,8 @@ void threadlet_queue_init(ThreadletQueue *queue,
qemu_mutex_init(&(queue->lock));
qemu_cond_init(&(queue->cond));
}
+
+void threadlet_init(void)
+{
+ threadlet_register_signal_handler();
+}
diff --git a/qemu-threadlets.h b/qemu-threadlets.h
index 6d9585b..5fd218a 100644
--- a/qemu-threadlets.h
+++ b/qemu-threadlets.h
@@ -45,4 +45,5 @@ extern int deque_threadletwork_on_queue(ThreadletQueue *queue,
extern int deque_threadletwork(ThreadletWork *work);
extern void threadlet_queue_init(ThreadletQueue *queue, int max_threads,
int min_threads);
+extern void threadlet_init(void);
#endif
diff --git a/vl.c b/vl.c
index df414ef..7b9a425 100644
--- a/vl.c
+++ b/vl.c
@@ -148,6 +148,7 @@ int main(int argc, char **argv)
#include "qemu-config.h"
#include "qemu-objects.h"
#include "qemu-options.h"
+#include "qemu-threadlets.h"
#ifdef CONFIG_VIRTFS
#include "fsdev/qemu-fsdev.h"
#endif
@@ -2922,6 +2923,8 @@ int main(int argc, char **argv, char **envp)
exit(1);
}
+ threadlet_init();
+
/* init generic devices */
if (qemu_opts_foreach(qemu_find_opts("device"), device_init_func, NULL, 1) != 0)
exit(1);
^ permalink raw reply related [flat|nested] 8+ messages in thread