[PATCH 0/5] Kernel memory accounting container (v4)

[PATCH 0/5] Kernel memory accounting container (v4)

[Pavel Emelyanov]

Long time ago we decided to start memory control with the
user memory container. Now this container in -mm tree and
I think we can start with (at least discussion of) the
kmem one.

Changes since v.3:
* moved alloc/free notification into slow path and make
  "notify-able" caches walk this path always;
* introduced some optimization for the case, when there's
  only one listener for SLUB events (saves more that 10%
  of performance);
* ported on 2.6.23-rc6-mm1 tree.

Changes since v.2:
* introduced generic notifiers for slub. right now there
  are only events, needed by accounting, but this set can
  be extended in the future;
* moved the controller core into separate file, so that
  its extension and/or porting on slAb will look more 
  logical;
* fixed this message :).

Changes since v.1:
* fixed Paul's comment about subsystem registration;
* return ERR_PTR from ->create callback, not NULL;
* make container-to-object assignment in rcu-safe section;
* make turning accounting on and off with "1" and "0".

============================================================

First of all - why do we need this kind of control. The major
"pros" is that kernel memory control protects the system
from DoS attacks by processes that live in container. As our
experience shows many exploits simply do not work in the
container with limited kernel memory.

I can split the kernel memory container into 4 parts:

1. kmalloc-ed objects control
2. vmalloc-ed objects control
3. buddy allocated pages control
4. kmem_cache_alloc-ed objects control

the control of first tree types of objects has one peculiarity:
one need to explicitly point out which allocations he wants to
account and this becomes not-configurable and is to be discussed.

On the other hands such objects as anon_vma-s, file-s, sighangds,
vfsmounts, etc are created by user request always and should
always be accounted. Fortunately they are allocated from their
own caches and thus the whole kmem cache can be accountable.

This is exactly what this patchset does - it adds the ability
to account for the total size of kmem-cache-allocated objects
from specified kmem caches.

This is based on the SLUB allocator, Paul's containers and the
resource counters I made for RSS controller and which are in
-mm tree already.

To play with it, one need to mount the container file system
with -o kmem and then mark some caches as accountable via
/sys/slab/<cache_name>/cache_notify.

As I have already told kmalloc caches cannot be accounted easily
so turning the accounting on for them will fail with -EINVAL.

Turning the accounting off is possible only if the cache has
no objects. This is done so because turning accounting off
implies unaccounting of all the objects in the cache, but due
to full-pages in slub are not stored in any lists (usually)
this is impossible to do so, however I'm open for discussion
of how to make this work.

Thanks,
Pavel

[PATCH 1/4] Add notification about some major slab events

[Pavel Emelyanov]

According to Christoph, there are already multiple people who 
want to control slab allocations and track memory for various 
reasons. So this is an introduction of such a hooks.

Currently, functions that are to call the notifiers are empty
and marked as "weak". Thus, if there's only _one_ listener
to these events, it can happily link with the vmlinux and
handle the events with more than 10% of performance saved.

The events tracked are:
1. allocation of an object;
2. freeing of an object;
3. allocation of a new page for objects;
4. freeing this page.

More events can be added on demand.

The kmem cache marked with SLAB_NOTIFY flag will cause all the
events above to generate notifications. By default no caches
come with this flag.

The events are generated on slow paths only and as soon as the
cache is marked as SLAB_NOTIFY, it will always use them for
allocation.

Signed-off-by: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>

---

diff --git a/include/linux/slab.h b/include/linux/slab.h
index f3a8eec..68d8e65 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -28,6 +28,7 @@
 #define SLAB_DESTROY_BY_RCU	0x00080000UL	/* Defer freeing slabs to RCU */
 #define SLAB_MEM_SPREAD		0x00100000UL	/* Spread some memory over cpuset */
 #define SLAB_TRACE		0x00200000UL	/* Trace allocations and frees */
+#define SLAB_NOTIFY		0x00400000UL	/* Notify major events */
 
 /* The following flags affect the page allocator grouping pages by mobility */
 #define SLAB_RECLAIM_ACCOUNT	0x00020000UL		/* Objects are reclaimable */
diff --git a/mm/slub.c b/mm/slub.c
index ac4f157..b5af598 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1040,6 +1040,29 @@ static inline unsigned long kmem_cache_f
 }
 #define slub_debug 0
 #endif
+
+int __attribute__ ((weak))
+slub_alloc_notify(struct kmem_cache *cachep, void *obj, gfp_t gfp)
+{
+	return 0;
+}
+
+void __attribute__ ((weak))
+slub_free_notify(struct kmem_cache *cachep, void *obj)
+{
+}
+
+int __attribute__ ((weak))
+slub_newpage_notify(struct kmem_cache *cachep, struct page *pg, gfp_t gfp)
+{
+	return 0;
+}
+
+void __attribute__ ((weak))
+slub_freepage_notify(struct kmem_cache *cachep, struct page *pg)
+{
+}
+
 /*
  * Slab allocation and freeing
  */
@@ -1063,7 +1162,11 @@ static struct page *allocate_slab(struct
 		page = alloc_pages_node(node, flags, s->order);
 
 	if (!page)
-		return NULL;
+		goto out;
+
+	if ((s->flags & SLAB_NOTIFY) &&
+			slub_newpage_notify(s, page, flags) < 0)
+		goto out_free;
 
 	mod_zone_page_state(page_zone(page),
 		(s->flags & SLAB_RECLAIM_ACCOUNT) ?
@@ -1071,6 +1174,11 @@ static struct page *allocate_slab(struct
 		pages);
 
 	return page;
+
+out_free:
+	__free_pages(page, s->order);
+out:
+	return NULL;
 }
 
 static void setup_object(struct kmem_cache *s, struct page *page,
@@ -1158,6 +1266,9 @@ static void rcu_free_slab(struct rcu_hea
 
 static void free_slab(struct kmem_cache *s, struct page *page)
 {
+	if (s->flags & SLAB_NOTIFY)
+		slub_freepage_notify(s, page);
+
 	if (unlikely(s->flags & SLAB_DESTROY_BY_RCU)) {
 		/*
 		 * RCU free overloads the RCU head over the LRU
@@ -1486,7 +1597,7 @@ load_freelist:
 	object = c->page->freelist;
 	if (unlikely(!object))
 		goto another_slab;
-	if (unlikely(SlabDebug(c->page)))
+	if (unlikely(SlabDebug(c->page)) || (s->flags & SLAB_NOTIFY))
 		goto debug;
 
 	object = c->page->freelist;
@@ -1545,12 +1656,20 @@ new_slab:
 	return NULL;
 debug:
 	object = c->page->freelist;
-	if (!alloc_debug_processing(s, c->page, object, addr))
+	if (SlabDebug(c->page) &&
+			!alloc_debug_processing(s, c->page, object, addr))
 		goto another_slab;
 
+	if ((s->flags & SLAB_NOTIFY) &&
+			slub_alloc_notify(s, object, gfpflags) < 0) {
+		object = NULL;
+		goto out;
+	}
+
 	c->page->inuse++;
 	c->page->freelist = object[c->offset];
 	c->node = -1;
+out:
 	slab_unlock(c->page);
 	return object;
 }
@@ -1620,7 +1739,7 @@ static void __slab_free(struct kmem_cach
 
 	slab_lock(page);
 
-	if (unlikely(SlabDebug(page)))
+	if (unlikely(SlabDebug(page)) || (s->flags & SLAB_NOTIFY))
 		goto debug;
 checks_ok:
 	prior = object[offset] = page->freelist;
@@ -1657,8 +1776,12 @@ slab_empty:
 	return;
 
 debug:
-	if (!free_debug_processing(s, page, x, addr))
+	if (SlabDebug(page) && !free_debug_processing(s, page, x, addr))
 		goto out_unlock;
+
+	if (s->flags & SLAB_NOTIFY)
+		slub_free_notify(s, x);
+
 	goto checks_ok;
 }

Re: [PATCH 1/4] Add notification about some major slab events

[Christoph Lameter]

On Fri, 21 Sep 2007, Pavel Emelyanov wrote:

> @@ -1486,7 +1597,7 @@ load_freelist:
>  	object = c->page->freelist;
>  	if (unlikely(!object))
>  		goto another_slab;
> -	if (unlikely(SlabDebug(c->page)))
> +	if (unlikely(SlabDebug(c->page)) || (s->flags & SLAB_NOTIFY))
>  		goto debug;

There is no need to check s->flags & SLAB_NOTIFY here. Just make sure that 
SlabDebug() is always set on allocated slabs. Set SlabDebug when a slab 
page is allocated is sufficient.
  
>  debug:
>  	object = c->page->freelist;
> -	if (!alloc_debug_processing(s, c->page, object, addr))
> +	if (SlabDebug(c->page) &&
> +			!alloc_debug_processing(s, c->page, object, addr))
>  		goto another_slab;
>  

SlabDebug will always be set and does not need to be tested.

> +	if ((s->flags & SLAB_NOTIFY) &&
> +			slub_alloc_notify(s, object, gfpflags) < 0) {
> +		object = NULL;
> +		goto out;
> +	}

Looks like the above piece is the only addition we need in __slab_alloc().

> @@ -1620,7 +1739,7 @@ static void __slab_free(struct kmem_cach
>  
>  	slab_lock(page);
>  
> -	if (unlikely(SlabDebug(page)))
> +	if (unlikely(SlabDebug(page)) || (s->flags & SLAB_NOTIFY))
>  		goto debug;

Not needed either.

>  checks_ok:
>  	prior = object[offset] = page->freelist;
> @@ -1657,8 +1776,12 @@ slab_empty:
>  	return;
>  
>  debug:
> -	if (!free_debug_processing(s, page, x, addr))
> +	if (SlabDebug(page) && !free_debug_processing(s, page, x, addr))
>  		goto out_unlock;

Ditto.

> +
> +	if (s->flags & SLAB_NOTIFY)
> +		slub_free_notify(s, x);
> +

Yup we need this for __slab_free.

[PATCH 2/5] Generic notifiers for SLUB events

[Pavel Emelyanov]

If the user wants more than one listener for SLUB event,
it can register them all as notifier_block-s so all of
them will be notified.

This costs us about 10% of performance loss, in comparison
with static linking.

The selected method of notification is srcu notifier blocks.
This is selected because the "call" path, i.e. when the 
notification is done, is lockless and at the same time the
handlers can sleep. Neither regular nor atomic notifiers
provide such facilities.

Signed-off-by: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>

---

diff --git a/init/Kconfig b/init/Kconfig
index 0bb211a..326fd55 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -593,6 +599,16 @@ config SLUB_DEBUG
 	  SLUB sysfs support. /sys/slab will not exist and there will be
 	  no support for cache validation etc.
 
+config SLUB_NOTIFY
+	default y
+	bool "Enable SLUB events generic notification"
+	depends on SLUB
+	help
+	  When Y, this option enables generic notifications of some major
+	  slub events. However, if you do know that there will be the
+	  only listener for them, you may say N here, so that callbacks
+	  will be called directly.
+
 choice
 	prompt "Choose SLAB allocator"
 	default SLUB
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 40801e7..fd9a3d4 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -200,4 +202,20 @@ static __always_inline void *kmalloc_nod
 }
 #endif
 
+struct slub_notify_struct {
+	struct kmem_cache *cachep;
+	void *objp;
+	gfp_t gfp;
+};
+
+enum {
+	SLUB_ALLOC,
+	SLUB_FREE,
+	SLUB_NEWPAGE,
+	SLUB_FREEPAGE,
+};
+
+int slub_register_notifier(struct notifier_block *nb);
+void slub_unregister_notifier(struct notifier_block *nb);
+
 #endif /* _LINUX_SLUB_DEF_H */
diff --git a/mm/slub.c b/mm/slub.c
index ac4f157..b5af598 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1040,6 +1040,81 @@ static inline unsigned long kmem_cache_f
 #define slub_debug 0
 #endif
 
+/*
+ * notifiers
+ */
+
+#ifdef CONFIG_SLUB_NOTIFY
+static struct srcu_notifier_head slub_nb;
+
+static noinline
+int __slub_alloc_notify(int cmd_alloc, int cmd_free, struct kmem_cache *cachep,
+		void *obj, gfp_t gfp)
+{
+	int ret, called;
+	struct slub_notify_struct arg;
+
+	arg.cachep = cachep;
+	arg.objp = obj;
+	arg.gfp = gfp;
+
+	ret = __srcu_notifier_call_chain(&slub_nb, cmd_alloc, &arg,
+			-1, &called);
+	ret = notifier_to_errno(ret);
+
+	if (ret < 0)
+		__srcu_notifier_call_chain(&slub_nb, cmd_free, &arg,
+				called, NULL);
+
+	return ret;
+}
+
+static noinline
+void __slub_free_notify(int cmd, struct kmem_cache *cachep, void *obj)
+{
+	struct slub_notify_struct arg;
+
+	arg.cachep = cachep;
+	arg.objp = obj;
+	arg.gfp = 0;
+
+	srcu_notifier_call_chain(&slub_nb, cmd, &arg);
+}
+
+int slub_register_notifier(struct notifier_block *nb)
+{
+	return srcu_notifier_chain_register(&slub_nb, nb);
+}
+
+void slub_unregister_notifier(struct notifier_block *nb)
+{
+	srcu_notifier_chain_unregister(&slub_nb, nb);
+}
+
+static inline
+int slub_alloc_notify(struct kmem_cache *cachep, void *obj, gfp_t gfp)
+{
+	return __slub_alloc_notify(SLUB_ALLOC, SLUB_FREE, cachep, obj, gfp);
+}
+
+static inline
+void slub_free_notify(struct kmem_cache *cachep, void *obj)
+{
+	__slub_free_notify(SLUB_FREE, cachep, obj);
+}
+
+static inline
+int slub_newpage_notify(struct kmem_cache *cachep, struct page *pg, gfp_t gfp)
+{
+	return __slub_alloc_notify(SLUB_NEWPAGE, SLUB_FREEPAGE, cachep, pg, gfp);
+}
+
+static inline
+void slub_freepage_notify(struct kmem_cache *cachep, struct page *pg)
+{
+	__slub_free_notify(SLUB_FREEPAGE, cachep, pg);
+}
+#else
 int __attribute__ ((weak))
 slub_alloc_notify(struct kmem_cache *cachep, void *obj, gfp_t gfp)
 {
@@ -1060,6 +1040,7 @@ static inline unsigned long kmem_cache_f
 slub_freepage_notify(struct kmem_cache *cachep, struct page *pg)
 {
 }
+#endif
 
 /*
  * Slab allocation and freeing
@@ -2785,8 +2916,9 @@ void __init kmem_cache_init(void)
 #else
 	kmem_size = sizeof(struct kmem_cache);
 #endif
-
-
+#ifdef CONFIG_SLUB_NOTIFY
+	srcu_init_notifier_head(&slub_nb);
+#endif
 	printk(KERN_INFO "SLUB: Genslabs=%d, HWalign=%d, Order=%d-%d, MinObjects=%d,"
 		" CPUs=%d, Nodes=%d\n",
 		caches, cache_line_size(),

[PATCH 3/5] Switch caches notification dynamically

[Pavel Emelyanov]

The /sys/slab/<name>/cache_notify attribute controls
whether the cache <name> is to be accounted or not.

For the reasons described before kmalloc caches cannot
be turned on.

By default no caches are accountable. Simply make
  # echo -n 1 >  /sys/slab/<name>cache_notify
to turn notification of this cache on.

If we turn accounting on on some cache and this cache 
is merged with some other, this "other" will be notified
as well. We can solve this by disabling of cache merging.

Turning the notification off is possible only when this 
cache is empty. The reason for this is that the pages,
that are full of objects are not linked in any list, so
we wouldn't be able to walk these pages and notify others
that these objects are no longer tracked.

Signed-off-by: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>

---

diff --git a/mm/slub.c b/mm/slub.c
index ac4f157..b5af598 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3775,6 +3917,36 @@ static ssize_t defrag_ratio_store(struct
 SLAB_ATTR(defrag_ratio);
 #endif
 
+static ssize_t cache_notify_show(struct kmem_cache *s, char *buf)
+{
+	return sprintf(buf, "%d\n", !!(s->flags & SLAB_NOTIFY));
+}
+
+static ssize_t cache_notify_store(struct kmem_cache *s,
+		const char *buf, size_t length)
+{
+	if (buf[0] == '1') {
+		s->flags |= SLAB_NOTIFY;
+		return length;
+	}
+
+	if (buf[0] == '0') {
+		if (any_slab_objects(s))
+			/*
+			 * we cannot turn this off because of the
+			 * full slabs cannot be found in this case
+			 */
+			return -EBUSY;
+
+		s->flags &= ~SLAB_NOTIFY;
+		return length;
+	}
+
+	return -EINVAL;
+}
+
+SLAB_ATTR(cache_notify);
+
 static struct attribute * slab_attrs[] = {
 	&slab_size_attr.attr,
 	&object_size_attr.attr,
@@ -3805,6 +3984,7 @@ static struct attribute * slab_attrs[] =
 #ifdef CONFIG_NUMA
 	&defrag_ratio_attr.attr,
 #endif
+	&cache_notify_attr.attr,
 	NULL
 };

Re: [PATCH 3/5] Switch caches notification dynamically

[Christoph Lameter]

On Fri, 21 Sep 2007, Pavel Emelyanov wrote:

> The /sys/slab/<name>/cache_notify attribute controls
> whether the cache <name> is to be accounted or not.
> 
> For the reasons described before kmalloc caches cannot
> be turned on.

It looks like the patch is forbidding to turn the notification off? On is 
okay even if there are already objects present? Full slabs may exist that 
cannot be accounted for now. I guess that is okay because we only want 
to track new allocations?

Re: [PATCH 3/5] Switch caches notification dynamically

[Pavel Emelyanov]

Christoph Lameter wrote:
> On Fri, 21 Sep 2007, Pavel Emelyanov wrote:
> 
>> The /sys/slab/<name>/cache_notify attribute controls
>> whether the cache <name> is to be accounted or not.
>>
>> For the reasons described before kmalloc caches cannot
>> be turned on.
> 
> It looks like the patch is forbidding to turn the notification off? On is 
> okay even if there are already objects present? 

Yup. If we "on" the notifications we will just receive new events.

> Full slabs may exist that cannot be accounted for now. I guess that is 
> okay because we only want to track new allocations?


If we turn notifications off with full slabs in memory we won't be 
able to (in case of kmem accounting) release the page's metadata that 
the slub_newpage event attached to them.

We can make this by tracking all the full slabs, and at the moment of
"off" walk them and generate slab_free and slab_release_page events,
but does it worth doing it ever?

Thanks,
Pavel

[PATCH 4/5] Setup the container

[Pavel Emelyanov]

Attach the controller to the containers. This will work
with the SLUB allocator only. However, if we need I can
port this on SLAB (and maybe SLOB ;) ).

This setup is simple and stupid.

Signed-off-by: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>

---

diff --git a/include/linux/container_subsys.h b/include/linux/container_subsys.h
index 81d11c2..9dd90d9 100644
--- a/include/linux/container_subsys.h
+++ b/include/linux/container_subsys.h
@@ -36,3 +36,9 @@ SUBSYS(mem_container)
 #endif
 
 /* */
+
+#ifdef CONFIG_CONTAINER_KMEM
+SUBSYS(kmem)
+#endif
+
+/* */
diff --git a/init/Kconfig b/init/Kconfig
index 0bb211a..326fd55 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -353,6 +353,12 @@ config CONTAINER_MEM_CONT
 	  Provides a memory controller that manages both page cache and
 	  RSS memory.
 
+config CONTAINER_KMEM
+	bool "Kernel memory controller for containers"
+	depends on CONTAINERS && RESOURCE_COUNTERS && SLUB
+	help
+	  Provides a kernel memory usage control for containers
+
 config PROC_PID_CPUSET
 	bool "Include legacy /proc/<pid>/cpuset file"
 	depends on CPUSETS
diff --git a/mm/Makefile b/mm/Makefile
index 6237dd6..1cb7e6d 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -31,4 +31,5 @@ obj-$(CONFIG_MIGRATION) += migrate.o
 obj-$(CONFIG_SMP) += allocpercpu.o
 obj-$(CONFIG_QUICKLIST) += quicklist.o
 obj-$(CONFIG_CONTAINER_MEM_CONT) += memcontrol.o
+obj-$(CONFIG_CONTAINER_KMEM) += kmemcontrol.o
 
diff --git a/mm/kmemcontrol.c b/mm/kmemcontrol.c
new file mode 100644
index 0000000..a2c45bb
--- /dev/null
+++ b/mm/kmemcontrol.c
@@ -0,0 +1,123 @@
+/*
+ * kmemcontrol.c - Kernel Memory Controller
+ *
+ * Copyright 2007 OpenVZ SWsoft Inc
+ * Author: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/mm.h>
+#include <linux/container.h>
+#include <linux/res_counter.h>
+#include <linux/err.h>
+
+struct kmem_container {
+	struct container_subsys_state css;
+	struct res_counter res;
+};
+
+static inline
+struct kmem_container *css_to_kmem(struct container_subsys_state *css)
+{
+	return container_of(css, struct kmem_container, css);
+}
+
+static inline 
+struct kmem_container *container_to_kmem(struct container *cont)
+{
+	return css_to_kmem(container_subsys_state(cont, kmem_subsys_id));
+}
+
+static inline
+struct kmem_container *task_kmem_container(struct task_struct *tsk)
+{
+	return css_to_kmem(task_subsys_state(tsk, kmem_subsys_id));
+}
+
+/*
+ * containers interface
+ */
+
+static struct kmem_container init_kmem_container;
+
+static struct container_subsys_state *kmem_create(struct container_subsys *ss,
+		struct container *container)
+{
+	struct kmem_container *mem;
+
+	if (unlikely((container->parent) == NULL))
+		mem = &init_kmem_container;
+	else
+		mem = kzalloc(sizeof(struct kmem_container), GFP_KERNEL);
+
+	if (mem == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	res_counter_init(&mem->res);
+	return &mem->css;
+
+}
+
+static void kmem_destroy(struct container_subsys *ss,
+		struct container *container)
+{
+	kfree(container_to_kmem(container));
+}
+
+static ssize_t kmem_container_read(struct container *cont, struct cftype *cft,
+		struct file *file, char __user *userbuf, size_t nbytes,
+		loff_t *ppos)
+{
+	return res_counter_read(&container_to_kmem(cont)->res,
+			cft->private, userbuf, nbytes, ppos, NULL);
+}
+
+static ssize_t kmem_container_write(struct container *cont, struct cftype *cft,
+		struct file *file, const char __user *userbuf,
+		size_t nbytes, loff_t *ppos)
+{
+	return res_counter_write(&container_to_kmem(cont)->res,
+			cft->private, userbuf, nbytes, ppos, NULL);
+}
+
+static struct cftype kmem_files[] = {
+	{
+		.name = "usage",
+		.private = RES_USAGE,
+		.read = kmem_container_read,
+	},
+	{
+		.name = "limit",
+		.private = RES_LIMIT,
+		.write = kmem_container_write,
+		.read = kmem_container_read,
+	},
+	{
+		.name = "failcnt",
+		.private = RES_FAILCNT,
+		.read = kmem_container_read,
+	},
+};
+
+static int kmem_populate(struct container_subsys *ss, struct container *cnt)
+{
+	return container_add_files(cnt, ss, kmem_files, ARRAY_SIZE(kmem_files));
+}
+
+struct container_subsys kmem_subsys = {
+	.name = "kmem",
+	.create = kmem_create,
+	.destroy  = kmem_destroy,
+	.populate = kmem_populate,
+	.subsys_id = kmem_subsys_id,
+	.early_init = 1,
+};

[PATCH 5/5] Account for the slub objects

[Pavel Emelyanov]

The struct page gets an extra pointer (just like it has with
the RSS controller) and this pointer points to the array of
the kmem_container pointers - one for each object stored on
that page itself.

Thus the i'th object on the page is accounted to the container
pointed by the i'th pointer on that array and when the object
is freed we unaccount its size to this particular container,
not the container current task belongs to.

This is done so, because the context objects are freed is most
often not the same as the one this objects was allocated in
(due to RCU and reference counters).

Signed-off-by: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>

---

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 48df4b4..1a41901 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -83,9 +83,14 @@ struct page {
 	void *virtual;			/* Kernel virtual address (NULL if
 					   not kmapped, ie. highmem) */
 #endif /* WANT_PAGE_VIRTUAL */
+	union {
 #ifdef CONFIG_CONTAINER_MEM_CONT
-	unsigned long page_container;
+		unsigned long page_container;
+#endif
+#ifdef CONFIG_CONTAINER_KMEM
+		struct kmem_container **containers;
 #endif
+	};
 #ifdef CONFIG_PAGE_OWNER
 	int order;
 	unsigned int gfp_mask;
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 40801e7..fd9a3d4 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -69,6 +69,8 @@ struct kmem_cache {
 #endif
 };
 
+int slab_index(void *p, struct kmem_cache *s, void *addr);
+
 /*
  * Kmalloc subsystem.
  */
diff --git a/mm/kmemcontrol.c b/mm/kmemcontrol.c
new file mode 100644
index 0000000..a2c45bb
--- /dev/null
+++ b/mm/kmemcontrol.c
@@ -13,6 +13,9 @@
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
+ *
+ * Changelog:
+ *   2007 Pavel Emelyanov : Add slub accounting
  */
 
 #include <linux/mm.h>
@@ -121,3 +124,128 @@
 	.subsys_id = kmem_subsys_id,
 	.early_init = 1,
 };
+
+/*
+ * slub accounting
+ */
+
+int slub_newpage_notify(struct kmem_cache *s, struct page *pg, gfp_t flags)
+{
+	struct kmem_container **ptr;
+
+	ptr = kzalloc(s->objects * sizeof(struct kmem_container *), flags);
+	if (ptr == NULL)
+		return -ENOMEM;
+
+	pg->containers = ptr;
+	return 0;
+}
+
+void slub_freepage_notify(struct kmem_cache *s, struct page *pg)
+{
+	struct kmem_container **ptr;
+
+	ptr = pg->containers;
+	if (ptr == NULL)
+		return;
+
+	kfree(ptr);
+	pg->containers = NULL;
+}
+
+int slub_alloc_notify(struct kmem_cache *s, void *obj, gfp_t gfp)
+{
+	struct page *pg;
+	struct kmem_container *cnt;
+	struct kmem_container **obj_container;
+
+	pg = virt_to_head_page(obj);
+	obj_container = pg->containers;
+	if (unlikely(obj_container == NULL)) {
+		/*
+		 * turned on after some objects were allocated
+		 */
+		if (slub_newpage_notify(s, pg, gfp) < 0)
+			goto err;
+
+		obj_container = pg->containers;
+	}
+
+	rcu_read_lock();
+	cnt = task_kmem_container(current);
+	if (res_counter_charge(&cnt->res, s->size))
+		goto err_locked;
+
+	css_get(&cnt->css);
+	rcu_read_unlock();
+	obj_container[slab_index(obj, s, page_address(pg))] = cnt;
+	return 0;
+
+err_locked:
+	rcu_read_unlock();
+err:
+	return -ENOMEM;
+}
+
+void slub_free_notify(struct kmem_cache *s, void *obj)
+{
+	struct page *pg;
+	struct kmem_container *cnt;
+	struct kmem_container **obj_container;
+
+	pg = virt_to_head_page(obj);
+	obj_container = pg->containers;
+	if (obj_container == NULL)
+		return;
+
+	obj_container += slab_index(obj, s, page_address(pg));
+	cnt = *obj_container;
+	if (cnt == NULL)
+		return;
+
+	res_counter_uncharge(&cnt->res, s->size);
+	*obj_container = NULL;
+	css_put(&cnt->css);
+}
+
+#ifdef CONFIG_SLUB_NOTIFY
+static int kmem_notify(struct notifier_block *nb, unsigned long cmd, void *arg)
+{
+	int ret;
+	struct slub_notify_struct *ns;
+
+	ns = (struct slub_notify_struct *)arg;
+
+	switch (cmd) {
+	case SLUB_ALLOC:
+		ret = slub_alloc_notify(ns->cachep, ns->objp, ns->gfp);
+		break;
+	case SLUB_FREE:
+		ret = 0;
+		slub_free_notify(ns->cachep, ns->objp);
+		break;
+	case SLUB_NEWPAGE:
+		ret = slub_newpage_notify(ns->cachep, ns->objp, ns->gfp);
+		break;
+	case SLUB_FREEPAGE:
+		ret = 0;
+		slub_freepage_notify(ns->cachep, ns->objp);
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+
+	return (ret < 0) ? notifier_from_errno(ret) : NOTIFY_OK;
+}
+
+static struct notifier_block kmem_block = {
+	.notifier_call = kmem_notify,
+};
+
+static int kmem_subsys_register(void)
+{
+	return slub_register_notifier(&kmem_block);
+}
+
+__initcall(kmem_subsys_register);
+#endif
diff --git a/mm/slub.c b/mm/slub.c
index ac4f157..b5af598 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -327,7 +327,7 @@ static inline void set_freepointer(struc
 	for (__p = (__free); __p; __p = get_freepointer((__s), __p))
 
 /* Determine object index from a given position */
-static inline int slab_index(void *p, struct kmem_cache *s, void *addr)
+inline int slab_index(void *p, struct kmem_cache *s, void *addr)
 {
 	return (p - addr) / s->size;
 }
@@ -2360,6 +2483,14 @@ EXPORT_SYMBOL(kmem_cache_destroy);
 struct kmem_cache kmalloc_caches[PAGE_SHIFT] __cacheline_aligned;
 EXPORT_SYMBOL(kmalloc_caches);
 
+static inline int is_kmalloc_cache(struct kmem_cache *s)
+{
+	int km_idx;
+
+	km_idx = s - kmalloc_caches;
+	return km_idx >= 0 && km_idx < ARRAY_SIZE(kmalloc_caches);
+}
+
 #ifdef CONFIG_ZONE_DMA
 static struct kmem_cache *kmalloc_caches_dma[PAGE_SHIFT];
 #endif
@@ -2811,6 +2943,16 @@ static int slab_unmergeable(struct kmem_
 	if (s->refcount < 0)
 		return 1;
 
+#ifdef CONFIG_CONTAINER_KMEM
+	/*
+	 * many caches that can be accountable are usually merged with
+	 * kmalloc caches, which are disabled for accounting for a while
+	 */
+
+	if (is_kmalloc_cache(s))
+		return 1;
+#endif
+
 	return 0;
 }
 
@@ -3775,6 +3917,13 @@ static ssize_t defrag_ratio_store(struct
 		const char *buf, size_t length)
 {
 	if (buf[0] == '1') {
+#ifdef CONFIG_CONTAINER_KMEM
+		if (is_kmalloc_cache(s))
+			/*
+			 * cannot just make these caches accountable
+			 */
+			return -EINVAL;
+#endif
 		s->flags |= SLAB_NOTIFY;
 		return length;
 	}

Re: [PATCH 0/5] Kernel memory accounting container (v4)

[Balbir Singh]

Pavel Emelyanov wrote:
> Long time ago we decided to start memory control with the
> user memory container. Now this container in -mm tree and
> I think we can start with (at least discussion of) the
> kmem one.
> 

Hi, Pavel,

Yes, I remember the entire discussion. Also in the TODO
list is an mlock() controller and a virtual memory
controller. Just wanted to ensure that they are still
in the TODO list.

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL

[PATCH 0/4] Kernel memory accounting container (v3)

[Pavel Emelyanov]

Long time ago we decided to start memory control with the
user memory container. Now this container in -mm tree and
I think we can start with (at least discussion of) the
kmem one.

Changes from v.2:
* introduced generic notifiers for slub. right now there
  are only events, needed by accounting, but this set can
  be extended in the future;
* moved the controller core into separate file, so that
  its extension and/or porting on slAb will look more 
  logical;
* fixed this message :).

Changes from v.1:
* fixed Paul's comment about subsystem registration;
* return ERR_PTR from ->create callback, not NULL;
* make container-to-object assignment in rcu-safe section;
* make turning accounting on and off with "1" and "0".

============================================================

First of all - why do we need this kind of control. The major
"pros" is that kernel memory control protects the system
from DoS attacks by processes that live in container. As our
experience shows many exploits simply do not work in the
container with limited kernel memory.

I can split the kernel memory container into 4 parts:

1. kmalloc-ed objects control
2. vmalloc-ed objects control
3. buddy allocated pages control
4. kmem_cache_alloc-ed objects control

the control of first tree types of objects has one peculiarity:
one need to explicitly point out which allocations he wants to
account and this becomes not-configurable and is to be discussed.

On the other hands such objects as anon_vma-s, file-s, sighangds,
vfsmounts, etc are created by user request always and should
always be accounted. Fortunately they are allocated from their
own caches and thus the whole kmem cache can be accountable.

This is exactly what this patchset does - it adds the ability
to account for the total size of kmem-cache-allocated objects
from specified kmem caches.

This is based on the SLUB allocator, Paul's containers and the
resource counters I made for RSS controller and which are in
-mm tree already.

To play with it, one need to mount the container file system
with -o kmem and then mark some caches as accountable via
/sys/slab/<cache_name>/cache_account.

As I have already told kmalloc caches cannot be accounted easily
so turning the accounting on for them will fail with -EINVAL.
Turning the accounting off is possible only if the cache has
no objects. This is done so because turning accounting off
implies unaccounting of all the objects in the cache, but due
to full-pages in slub are not stored in any lists (usually)
this is impossible to do so, however I'm open for discussion
of how to make this work.

The patches are applicable to the latest Morton's tree.

Thanks,
Pavel

[PATCH 1/4] Add notification about some major slab events

[Pavel Emelyanov]

According to Christoph, there are already multiple people who 
want to control slab allocations and track memory for various 
reasons. So this is an introduction of such a hooks.

The selected method of notification is srcu notifier blocks.
This is selected because the "call" path, i.e. when the 
notification is done, is lockless and at the same time 
notification handlers can sleep. Neither regular nor atomic
notifiers provide such facilities.

The events tracked are:
1. allocation of an object
2. freeing of an onbject
3. allocation of a new page for objects
4. freeing this page

More events can be added on demand.

The kmem cache marked with SLAB_NOTIFY flag will cause all the
events above to generate notifications. By default no caches
come with this flag.

To preserve the fast-paths and keep the stack from growing
the checks for the flag are made in a separate inline functions
and the actual notification is done in noinline ones.

Hopefully, this looks close to how Christoph sees it :)

Signed-off-by: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>

---

 include/linux/slab.h     |    1 
 include/linux/slub_def.h |   16 +++++++
 mm/slub.c                |  105 ++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 121 insertions(+), 1 deletion(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 3a5bad3..a3bd620 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -28,6 +28,7 @@
 #define SLAB_DESTROY_BY_RCU	0x00080000UL	/* Defer freeing slabs to RCU */
 #define SLAB_MEM_SPREAD		0x00100000UL	/* Spread some memory over cpuset */
 #define SLAB_TRACE		0x00200000UL	/* Trace allocations and frees */
+#define SLAB_NOTIFY		0x00400000UL	/* Notify major events */
 
 /* The following flags affect the page allocator grouping pages by mobility */
 #define SLAB_RECLAIM_ACCOUNT	0x00020000UL		/* Objects are reclaimable */
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index d65159d..547777e 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -200,4 +202,20 @@ static __always_inline void *kmalloc_nod
 }
 #endif
 
+struct slub_notify_struct {
+	struct kmem_cache *cachep;
+	void *objp;
+	gfp_t gfp;
+};
+
+enum {
+	SLUB_ALLOC,
+	SLUB_FREE,
+	SLUB_NEWPAGE,
+	SLUB_FREEPAGE,
+};
+
+int slub_register_notifier(struct notifier_block *nb);
+void slub_unregister_notifier(struct notifier_block *nb);
+
 #endif /* _LINUX_SLUB_DEF_H */
diff --git a/mm/slub.c b/mm/slub.c
index 1802645..bfb7c21 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1013,6 +1013,91 @@ static inline void add_full(struct kmem_
 static inline void kmem_cache_open_debug_check(struct kmem_cache *s) {}
 #define slub_debug 0
 #endif
+
+/*
+ * notifiers
+ */
+
+static struct srcu_notifier_head slub_nb;
+
+static noinline
+int __slub_alloc_notify(int cmd_alloc, int cmd_free, struct kmem_cache *cachep,
+		void *obj, gfp_t gfp)
+{
+	int ret, called;
+	struct slub_notify_struct arg;
+
+	arg.cachep = cachep;
+	arg.objp = obj;
+	arg.gfp = gfp;
+
+	ret = __srcu_notifier_call_chain(&slub_nb, cmd_alloc, &arg,
+			-1, &called);
+	ret = notifier_to_errno(ret);
+
+	if (ret < 0)
+		__srcu_notifier_call_chain(&slub_nb, cmd_free, &arg,
+				called, NULL);
+
+	return ret;
+}
+
+static noinline
+void __slub_free_notify(int cmd, struct kmem_cache *cachep, void *obj)
+{
+	struct slub_notify_struct arg;
+
+	arg.cachep = cachep;
+	arg.objp = obj;
+	arg.gfp = 0;
+
+	srcu_notifier_call_chain(&slub_nb, cmd, &arg);
+}
+
+int slub_register_notifier(struct notifier_block *nb)
+{
+	return srcu_notifier_chain_register(&slub_nb, nb);
+}
+
+void slub_unregister_notifier(struct notifier_block *nb)
+{
+	srcu_notifier_chain_unregister(&slub_nb, nb);
+}
+
+/*
+ * fastpath hooks
+ */
+
+static inline
+int slub_alloc_notify(struct kmem_cache *cachep, void *obj, gfp_t gfp)
+{
+	return (unlikely(cachep->flags & SLAB_NOTIFY)) ?
+		__slub_alloc_notify(SLUB_ALLOC, SLUB_FREE,
+				cachep, obj, gfp) : 0;
+}
+
+static inline
+void slub_free_notify(struct kmem_cache *cachep, void *obj)
+{
+	if (unlikely(cachep->flags & SLAB_NOTIFY))
+		__slub_free_notify(SLUB_FREE, cachep, obj);
+}
+
+static inline
+int slub_newpage_notify(struct kmem_cache *cachep, struct page *pg, gfp_t gfp)
+{
+	return (unlikely(cachep->flags & SLAB_NOTIFY)) ?
+		__slub_alloc_notify(SLUB_NEWPAGE, SLUB_FREEPAGE,
+				cachep, pg, gfp) : 0;
+}
+
+static inline
+void slub_freepage_notify(struct kmem_cache *cachep, struct page *pg)
+{
+	if (unlikely(cachep->flags & SLAB_NOTIFY))
+		__slub_free_notify(SLUB_FREEPAGE, cachep, pg);
+}
+
 /*
  * Slab allocation and freeing
  */
@@ -1036,7 +1121,10 @@ static struct page *allocate_slab(struct
 		page = alloc_pages_node(node, flags, s->order);
 
 	if (!page)
-		return NULL;
+		goto out;
+
+	if (slub_newpage_notify(s, page, flags) < 0)
+		goto out_free;
 
 	mod_zone_page_state(page_zone(page),
 		(s->flags & SLAB_RECLAIM_ACCOUNT) ?
@@ -1044,6 +1132,11 @@ static struct page *allocate_slab(struct
 		pages);
 
 	return page;
+
+out_free:
+	__free_pages(page, s->order);
+out:
+	return NULL;
 }
 
 static void setup_object(struct kmem_cache *s, struct page *page,
@@ -1136,6 +1229,8 @@ static void rcu_free_slab(struct rcu_hea
 
 static void free_slab(struct kmem_cache *s, struct page *page)
 {
+	slub_freepage_notify(s, page);
+
 	if (unlikely(s->flags & SLAB_DESTROY_BY_RCU)) {
 		/*
 		 * RCU free overloads the RCU head over the LRU
@@ -1555,6 +1650,11 @@ static void __always_inline *slab_alloc(
 	}
 	local_irq_restore(flags);
 
+	if (object && slub_alloc_notify(s, object, gfpflags) < 0) {
+		kmem_cache_free(s, object);
+		return NULL;
+	}
+
 	if (unlikely((gfpflags & __GFP_ZERO) && object))
 		memset(object, 0, c->objsize);
 
@@ -1651,6 +1751,8 @@ static void __always_inline slab_free(st
 	unsigned long flags;
 	struct kmem_cache_cpu *c;
 
+	slub_free_notify(s, x);
+
 	local_irq_save(flags);
 	debug_check_no_locks_freed(object, s->objsize);
 	c = get_cpu_slab(s, smp_processor_id());
@@ -2764,6 +2874,7 @@ void __init kmem_cache_init(void)
 	kmem_size = sizeof(struct kmem_cache);
 #endif
 
+	srcu_init_notifier_head(&slub_nb);
 
 	printk(KERN_INFO "SLUB: Genslabs=%d, HWalign=%d, Order=%d-%d, MinObjects=%d,"
 		" CPUs=%d, Nodes=%d\n",

Re: [PATCH 1/4] Add notification about some major slab events

[Christoph Lameter]

On Mon, 17 Sep 2007, Pavel Emelyanov wrote:

> @@ -1036,7 +1121,10 @@ static struct page *allocate_slab(struct
>  		page = alloc_pages_node(node, flags, s->order);
>  
>  	if (!page)
> -		return NULL;
> +		goto out;
> +
> +	if (slub_newpage_notify(s, page, flags) < 0)
> +		goto out_free;
>  
>  	mod_zone_page_state(page_zone(page),
>  		(s->flags & SLAB_RECLAIM_ACCOUNT) ?
> @@ -1044,6 +1132,11 @@ static struct page *allocate_slab(struct
>  		pages);
>  
>  	return page;
> +
> +out_free:
> +	__free_pages(page, s->order);
> +out:
> +	return NULL;
>  }

Ok that looks sane.

>  static void setup_object(struct kmem_cache *s, struct page *page,
> @@ -1136,6 +1229,8 @@ static void rcu_free_slab(struct rcu_hea
>  
>  static void free_slab(struct kmem_cache *s, struct page *page)
>  {
> +	slub_freepage_notify(s, page);
> +
>  	if (unlikely(s->flags & SLAB_DESTROY_BY_RCU)) {
>  		/*
>  		 * RCU free overloads the RCU head over the LRU

Ditto.

> @@ -1555,6 +1650,11 @@ static void __always_inline *slab_alloc(
>  	}
>  	local_irq_restore(flags);
>  
> +	if (object && slub_alloc_notify(s, object, gfpflags) < 0) {
> +		kmem_cache_free(s, object);
> +		return NULL;
> +	}
> +
>  	if (unlikely((gfpflags & __GFP_ZERO) && object))
>  		memset(object, 0, c->objsize);
>  

Please stay completely out of the fast path. No modifications to 
slab_alloc or slab_free please. It is possible to force all allocations of 
a particular slab of interest to use the slow path in __slab_alloc (maybe 
as a result of the slab page allocation hook returning a certain result 
code). See how the SLAB_DEBUG handling does it. You can adapt that and then do the 
object checks in __slab_alloc.

Re: [PATCH 1/4] Add notification about some major slab events

[Pavel Emelyanov]

Christoph Lameter wrote:
> On Mon, 17 Sep 2007, Pavel Emelyanov wrote:
> 
>> @@ -1036,7 +1121,10 @@ static struct page *allocate_slab(struct
>>  		page = alloc_pages_node(node, flags, s->order);
>>  
>>  	if (!page)
>> -		return NULL;
>> +		goto out;
>> +
>> +	if (slub_newpage_notify(s, page, flags) < 0)
>> +		goto out_free;
>>  
>>  	mod_zone_page_state(page_zone(page),
>>  		(s->flags & SLAB_RECLAIM_ACCOUNT) ?
>> @@ -1044,6 +1132,11 @@ static struct page *allocate_slab(struct
>>  		pages);
>>  
>>  	return page;
>> +
>> +out_free:
>> +	__free_pages(page, s->order);
>> +out:
>> +	return NULL;
>>  }
> 
> Ok that looks sane.
> 
>>  static void setup_object(struct kmem_cache *s, struct page *page,
>> @@ -1136,6 +1229,8 @@ static void rcu_free_slab(struct rcu_hea
>>  
>>  static void free_slab(struct kmem_cache *s, struct page *page)
>>  {
>> +	slub_freepage_notify(s, page);
>> +
>>  	if (unlikely(s->flags & SLAB_DESTROY_BY_RCU)) {
>>  		/*
>>  		 * RCU free overloads the RCU head over the LRU
> 
> Ditto.
> 
>> @@ -1555,6 +1650,11 @@ static void __always_inline *slab_alloc(
>>  	}
>>  	local_irq_restore(flags);
>>  
>> +	if (object && slub_alloc_notify(s, object, gfpflags) < 0) {
>> +		kmem_cache_free(s, object);
>> +		return NULL;
>> +	}
>> +
>>  	if (unlikely((gfpflags & __GFP_ZERO) && object))
>>  		memset(object, 0, c->objsize);
>>  
> 
> Please stay completely out of the fast path. No modifications to 
> slab_alloc or slab_free please. It is possible to force all allocations of 
> a particular slab of interest to use the slow path in __slab_alloc (maybe 
> as a result of the slab page allocation hook returning a certain result 
> code). See how the SLAB_DEBUG handling does it. You can adapt that and then do the 
> object checks in __slab_alloc.

That's true, but:
1. we perform only a flag check on a fast path
2. currently we cannot force the freeing of an object to go _always_ 
   through the slow __slab_free(), and thus the following situation is 
   possible:
     a. container A allocates an object and this object is 
        accounted to it
     b. the object is freed and gets into lockless freelist (but 
        stays accounted to A)
     c. container C allocates this object from the freelist 
        and thus get unaccounted amount of memory
  this discrepancy can grow up infinitely. Sure, we can mark some caches to
  go through the slow path even on freeing the objects, but isn't it the
  same as checking for SLAB_NOTIFY on fast paths?

Maybe it's worth having the notifiers under config option, so that those
who don't need this won't suffer at all?

Thanks,
Pavel

Re: [PATCH 1/4] Add notification about some major slab events

[Christoph Lameter]

On Tue, 18 Sep 2007, Pavel Emelyanov wrote:

> > Please stay completely out of the fast path. No modifications to 
> > slab_alloc or slab_free please. It is possible to force all allocations of 
> > a particular slab of interest to use the slow path in __slab_alloc (maybe 
> > as a result of the slab page allocation hook returning a certain result 
> > code). See how the SLAB_DEBUG handling does it. You can adapt that and then do the 
> > object checks in __slab_alloc.
> 
> That's true, but:
> 1. we perform only a flag check on a fast path

This is still going to slow down everyone else and I still think there is 
no need to do that.

> 2. currently we cannot force the freeing of an object to go _always_ 
>    through the slow __slab_free(), and thus the following situation is 
>    possible:
>      a. container A allocates an object and this object is 
>         accounted to it

At that point you could mark the slab as a slow slab by setting 
SLAB_DEBUG() so we always take the slow path for this slab.

>      b. the object is freed and gets into lockless freelist (but 
>         stays accounted to A)

B wont work if SLAB_DEBUG() is set. The fastpath is then disabled.

>      c. container C allocates this object from the freelist 
>         and thus get unaccounted amount of memory

>   this discrepancy can grow up infinitely. Sure, we can mark some caches to
>   go through the slow path even on freeing the objects, but isn't it the
>   same as checking for SLAB_NOTIFY on fast paths?

The other caches will then still perform up to speed.
 
> Maybe it's worth having the notifiers under config option, so that those
> who don't need this won't suffer at all?

I think you would want the container functionality to be available in 
distros. They may make the choice whether to enable the container 
functionality based on its impact. It is good if we can stash it away so 
that there is a negligible performance impact if its compiled in but off.

Re: [PATCH 1/4] Add notification about some major slab events

[Pavel Emelyanov]

[snip]

>> @@ -1555,6 +1650,11 @@ static void __always_inline *slab_alloc(
>>  	}
>>  	local_irq_restore(flags);
>>  
>> +	if (object && slub_alloc_notify(s, object, gfpflags) < 0) {
>> +		kmem_cache_free(s, object);
>> +		return NULL;
>> +	}
>> +
>>  	if (unlikely((gfpflags & __GFP_ZERO) && object))
>>  		memset(object, 0, c->objsize);
>>  
> 
> Please stay completely out of the fast path. No modifications to 
> slab_alloc or slab_free please. It is possible to force all allocations of 
> a particular slab of interest to use the slow path in __slab_alloc (maybe 
> as a result of the slab page allocation hook returning a certain result 
> code). See how the SLAB_DEBUG handling does it. You can adapt that and then do the 
> object checks in __slab_alloc.

I have run the kernbench test on the kernels with a) containers support
and b) containers and kmem accounting support but (!) turned off. The
results are:
                 a)             b)
Elapsed Time     768.500000     767.050000
User Time        679.360000     679.240000
System Time      87.020000      86.950000
Percent CPU      99.000000      99.000000
Context Switches 376891.000000  375407.000000
Sleeps           385377.000000  385426.000000

The test run was kernbench -n 1 -o 4 -M, the node is i386
DualCore Xeon 3.2GHz with 2Gb of RAM.

so the fast path is still fast, and we have two ways:
1. we keep the checks on the fastpath and have 0 overhead for
   unaccounted caches and some overhead for accounted;
2. we move the checks into the slow one and have 0 overhead for
   unaccounted caches and huge overhead for accounted.

I admit that I messed something, so shall I measure some 
other activity or use another HW?

Thanks,
Pavel

Re: [PATCH 1/4] Add notification about some major slab events

[Christoph Lameter]

On Wed, 19 Sep 2007, Pavel Emelyanov wrote:

> so the fast path is still fast, and we have two ways:
> 1. we keep the checks on the fastpath and have 0 overhead for
>    unaccounted caches and some overhead for accounted;

This stuff accumulates. I have a bad experience from SLAB. We are counting 
cycle counts and cachelines touched in the fastpath and this is going to 
add to them.

> 2. we move the checks into the slow one and have 0 overhead for
>    unaccounted caches and huge overhead for accounted.

Huge? Its not that huge.

> I admit that I messed something, so shall I measure some 
> other activity or use another HW?

You could use this module to test the cycles in the fastpath:


/* test-slub.c
 */


#include <linux/jiffies.h>
#include <linux/compiler.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/calc64.h>
#include <asm/timex.h>
#include <asm/system.h>

#define TEST_COUNT 10000

#define PARALLEL

#ifdef PARALLEL
#include <linux/completion.h>
#include <linux/sched.h>
#include <linux/workqueue.h>
#include <linux/kthread.h>

struct test_struct {
	struct task_struct *task;
	int cpu;
	int size;
	int count;
	void **v;
	void (*test_p1)(struct test_struct *);
	void (*test_p2)(struct test_struct *);
	unsigned long start;
	unsigned long stop1;
	unsigned long stop2;
} test[NR_CPUS];

/*
 * Allocate TEST_COUNT objects and later free them all again
 */
static void kmalloc_alloc_then_free_test_p1(struct test_struct *t)
{
	int i;

	for (i = 0; i < t->count; i++)
		t->v[i] = kmalloc(t->size, GFP_KERNEL);
}

static void kmalloc_alloc_then_free_test_p2(struct test_struct *t)
{
	int i;

	for (i = 0; i < t->count; i++)
		kfree(t->v[i]);
}

/*
 * Allocate TEST_COUNT objects. Free them immediately.
 */
static void kmalloc_alloc_free_test_p1(struct test_struct *t)
{
	int i;

	for (i = 0; i < TEST_COUNT; i++)
		kfree(kmalloc(t->size, GFP_KERNEL));
}

static atomic_t tests_running;
static DECLARE_COMPLETION(completion);
static int started;

static int test_func(void *private)
{
	struct test_struct *t = private;
	cpumask_t newmask = CPU_MASK_NONE;

        cpu_set(t->cpu, newmask);
        set_cpus_allowed(current, newmask);
	t->v = kmalloc(t->count * sizeof(void *), GFP_KERNEL);

	atomic_inc(&tests_running);
	wait_for_completion(&completion);
	t->start = get_cycles();
	t->test_p1(t);
	t->stop1 = get_cycles();
	if (t->test_p2)
		t->test_p2(t);
	t->stop2 = get_cycles();
	kfree(t->v);
	atomic_dec(&tests_running);
	set_current_state(TASK_UNINTERRUPTIBLE);
	schedule();
	return 0;
}

static void do_concurrent_test(void (*p1)(struct test_struct *),
		void (*p2)(struct test_struct *),
		int size, const char *name)
{
	int cpu;
	unsigned long time1 = 0;
	unsigned long time2 = 0;
	unsigned long sum1 = 0;
	unsigned long sum2 = 0;

	atomic_set(&tests_running, 0);
	started = 0;
	init_completion(&completion);

	for_each_online_cpu(cpu) {
		struct test_struct *t = &test[cpu];

		t->cpu = cpu;
		t->count = TEST_COUNT;
		t->test_p1 = p1;
		t->test_p2 = p2;
		t->size = size;
		t->task = kthread_run(test_func, t, "test%d", cpu);
		if (IS_ERR(t->task)) {
			printk("Failed to start test func\n");
			return;
		}
	}

	/* Wait till all processes are running */
	while (atomic_read(&tests_running) < num_online_cpus()) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule_timeout(10);
	}
	complete_all(&completion);
	while (atomic_read(&tests_running)) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule_timeout(10);
	}

	for_each_online_cpu(cpu)
		kthread_stop(test[cpu].task);

	printk(KERN_ALERT "%s(%d):", name, size);
	for_each_online_cpu(cpu) {
		struct test_struct *t = &test[cpu];

		time1 = t->stop1 - t->start;
		time2 = t->stop2 - t->stop1;
		sum1 += time1;
		sum2 += time2;
		printk(" %d=%lu", cpu, time1 / TEST_COUNT);
		if (p2)
			printk("/%lu", time2 / TEST_COUNT);
	}
	printk(" Average=%lu", sum1 / num_online_cpus() / TEST_COUNT);
	if (p2)
		printk("/%lu", sum2 / num_online_cpus() / TEST_COUNT);
	printk("\n");
	schedule_timeout(200);
}
#endif

static int slub_test_init(void)
{
	void **v = kmalloc(TEST_COUNT * sizeof(void *), GFP_KERNEL);
	unsigned int i;
	cycles_t time1, time2, time;
	long rem;
	int size;

	printk(KERN_ALERT "test init\n");

	printk(KERN_ALERT "Single thread testing\n");
	printk(KERN_ALERT "=====================\n");
	printk(KERN_ALERT "1. Kmalloc: Repeatedly allocate then free test\n");
	for (size = 8; size <= PAGE_SIZE << 2; size <<= 1) {
		time1 = get_cycles();
		for (i = 0; i < TEST_COUNT; i++) {
			v[i] = kmalloc(size, GFP_KERNEL);
		}
		time2 = get_cycles();
		time = time2 - time1;

		printk(KERN_ALERT "%i times kmalloc(%d) ", i, size);
		time = div_long_long_rem(time, TEST_COUNT, &rem);
		printk("-> %llu cycles ", time);

		time1 = get_cycles();
		for (i = 0; i < TEST_COUNT; i++) {
			kfree(v[i]);
		}
		time2 = get_cycles();
		time = time2 - time1;

		printk("kfree ");
		time = div_long_long_rem(time, TEST_COUNT, &rem);
		printk("-> %llu cycles\n", time);
	}

	printk(KERN_ALERT "2. Kmalloc: alloc/free test\n");
	for (size = 8; size <= PAGE_SIZE << 2; size <<= 1) {
		time1 = get_cycles();
		for (i = 0; i < TEST_COUNT; i++) {
			kfree(kmalloc(size, GFP_KERNEL));
		}
		time2 = get_cycles();
		time = time2 - time1;

		printk(KERN_ALERT "%i times kmalloc(%d)/kfree ", i, size);
		time = div_long_long_rem(time, TEST_COUNT, &rem);
		printk("-> %llu cycles\n", time);
	}
	kfree(v);
#ifdef PARALLEL
	printk(KERN_INFO "Concurrent allocs\n");
	printk(KERN_INFO "=================\n");
	for (i = 3; i <= PAGE_SHIFT; i++) {
		do_concurrent_test(kmalloc_alloc_then_free_test_p1,
			kmalloc_alloc_then_free_test_p2,
			1 << i, "Kmalloc N*alloc N*free");
	}
	for (i = 3; i <= PAGE_SHIFT; i++) {
		do_concurrent_test(kmalloc_alloc_free_test_p1, NULL,
			1 << i, "Kmalloc N*(alloc free)");
	}
#endif

	return -EAGAIN; /* Fail will directly unload the module */
}

static void slub_test_exit(void)
{
	printk(KERN_ALERT "test exit\n");
}

module_init(slub_test_init)
module_exit(slub_test_exit)

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mathieu Desnoyers");
MODULE_DESCRIPTION("SLUB test");