[Qemu-devel] [PULL v2 0/3] Block patches

[Qemu-devel] [PULL v2 0/3] Block patches

[Stefan Hajnoczi]

The following changes since commit bec9c64ef7be8063f1192608b83877bc5c9ea217:

  Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging (2018-02-13 18:24:08 +0000)

are available in the Git repository at:

  git://github.com/stefanha/qemu.git tags/block-pull-request

for you to fetch changes up to d2f668b74907cbd96d9df0774971768ed06de2f0:

  misc: fix spelling (2018-02-15 09:39:49 +0000)

----------------------------------------------------------------
Pull request

v2:
 * Dropped Fam's git-publish series because there is still ongoing discussion

----------------------------------------------------------------

Marc-André Lureau (1):
  misc: fix spelling

Stefan Hajnoczi (1):
  vl: pause vcpus before stopping iothreads

Wolfgang Bumiller (1):
  ratelimit: don't align wait time with slices

 include/qemu/ratelimit.h   | 11 +++++------
 util/qemu-coroutine-lock.c |  2 +-
 vl.c                       | 12 ++++++++++--
 3 files changed, 16 insertions(+), 9 deletions(-)

-- 
2.14.3

[Qemu-devel] [PULL v2 1/3] vl: pause vcpus before stopping iothreads

[Stefan Hajnoczi]

Commit dce8921b2baaf95974af8176406881872067adfa ("iothread: Stop threads
before main() quits") introduced iothread_stop_all() to avoid the
following virtio-scsi assertion failure:

  assert(blk_get_aio_context(d->conf.blk) == s->ctx);

Back then the assertion failed because when bdrv_close_all() made
d->conf.blk NULL, blk_get_aio_context() returned the global AioContext
instead of s->ctx.

The same assertion can still fail today when vcpus submit new I/O
requests after iothread_stop_all() has moved the BDS to the global
AioContext.

This patch hardens the iothread_stop_all() approach by pausing vcpus
before calling iothread_stop_all().

Note that the assertion failure is a race condition.  It is not possible
to reproduce it reliably.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20180201110708.8080-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 vl.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/vl.c b/vl.c
index 21878496ec..7a5554bc41 100644
--- a/vl.c
+++ b/vl.c
@@ -4767,10 +4767,18 @@ int main(int argc, char **argv, char **envp)
 
     main_loop();
     replay_disable_events();
+
+    /* The ordering of the following is delicate.  Stop vcpus to prevent new
+     * I/O requests being queued by the guest.  Then stop IOThreads (this
+     * includes a drain operation and completes all request processing).  At
+     * this point emulated devices are still associated with their IOThreads
+     * (if any) but no longer have any work to do.  Only then can we close
+     * block devices safely because we know there is no more I/O coming.
+     */
+    pause_all_vcpus();
     iothread_stop_all();
-
-    pause_all_vcpus();
     bdrv_close_all();
+
     res_free();
 
     /* vhost-user must be cleaned up before chardevs.  */
-- 
2.14.3

[Qemu-devel] [PULL v2 2/3] ratelimit: don't align wait time with slices

[Stefan Hajnoczi]

From: Wolfgang Bumiller <w.bumiller@proxmox.com>

It is possible for rate limited writes to keep overshooting a slice's
quota by a tiny amount causing the slice-aligned waiting period to
effectively halve the rate.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20180207071758.6818-1-w.bumiller@proxmox.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 include/qemu/ratelimit.h | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/include/qemu/ratelimit.h b/include/qemu/ratelimit.h
index 8dece483f5..1b38291823 100644
--- a/include/qemu/ratelimit.h
+++ b/include/qemu/ratelimit.h
@@ -36,7 +36,7 @@ typedef struct {
 static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
 {
     int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
-    uint64_t delay_slices;
+    double delay_slices;
 
     assert(limit->slice_quota && limit->slice_ns);
 
@@ -55,12 +55,11 @@ static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
         return 0;
     }
 
-    /* Quota exceeded. Calculate the next time slice we may start
-     * sending data again. */
-    delay_slices = (limit->dispatched + limit->slice_quota - 1) /
-        limit->slice_quota;
+    /* Quota exceeded. Wait based on the excess amount and then start a new
+     * slice. */
+    delay_slices = (double)limit->dispatched / limit->slice_quota;
     limit->slice_end_time = limit->slice_start_time +
-        delay_slices * limit->slice_ns;
+        (uint64_t)(delay_slices * limit->slice_ns);
     return limit->slice_end_time - now;
 }
 
-- 
2.14.3

[Qemu-devel] [PULL v2 3/3] misc: fix spelling

[Stefan Hajnoczi]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

s/pupulate/populate

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20180208162447.10851-1-marcandre.lureau@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 util/qemu-coroutine-lock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c
index 78fb79acf8..5a80c10690 100644
--- a/util/qemu-coroutine-lock.c
+++ b/util/qemu-coroutine-lock.c
@@ -89,7 +89,7 @@ void qemu_co_queue_run_restart(Coroutine *co)
      * invalid memory.  Therefore, use a temporary queue and do not touch
      * the "co" coroutine as soon as you enter another one.
      *
-     * In its turn resumed "co" can pupulate "co_queue_wakeup" queue with
+     * In its turn resumed "co" can populate "co_queue_wakeup" queue with
      * new coroutines to be woken up.  The caller, who has resumed "co",
      * will be responsible for traversing the same queue, which may cause
      * a different wakeup order but not any missing wakeups.
-- 
2.14.3

Re: [Qemu-devel] [PULL v2 0/3] Block patches

[Peter Maydell]

On 15 February 2018 at 09:42, Stefan Hajnoczi <stefanha@redhat.com> wrote:
> The following changes since commit bec9c64ef7be8063f1192608b83877bc5c9ea217:
>
>   Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging (2018-02-13 18:24:08 +0000)
>
> are available in the Git repository at:
>
>   git://github.com/stefanha/qemu.git tags/block-pull-request
>
> for you to fetch changes up to d2f668b74907cbd96d9df0774971768ed06de2f0:
>
>   misc: fix spelling (2018-02-15 09:39:49 +0000)
>
> ----------------------------------------------------------------
> Pull request
>
> v2:
>  * Dropped Fam's git-publish series because there is still ongoing discussion
>
> ----------------------------------------------------------------
>
> Marc-André Lureau (1):
>   misc: fix spelling
>
> Stefan Hajnoczi (1):
>   vl: pause vcpus before stopping iothreads
>
> Wolfgang Bumiller (1):
>   ratelimit: don't align wait time with slices
>
>  include/qemu/ratelimit.h   | 11 +++++------
>  util/qemu-coroutine-lock.c |  2 +-
>  vl.c                       | 12 ++++++++++--
>  3 files changed, 16 insertions(+), 9 deletions(-)

Applied, thanks.

-- PMM