From: Waiman Long <llong@redhat.com> To: Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@kernel.org>, Vladimir Davydov <vdavydov.dev@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Vlastimil Babka <vbabka@suse.cz>, Roman Gushchin <guro@fb.com>, Shakeel Butt <shakeelb@google.com> Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v5 2/3] mm: memcg/slab: Create a new set of kmalloc-cg-<n> caches Date: Wed, 12 May 2021 10:54:19 -0400 [thread overview] Message-ID: <0919aaab-cc08-f86d-1f9a-8ddfeed7bb31@redhat.com> (raw) In-Reply-To: <20210512145107.6208-1-longman@redhat.com> On 5/12/21 10:51 AM, Waiman Long wrote: > There are currently two problems in the way the objcg pointer array > (memcg_data) in the page structure is being allocated and freed. > > On its allocation, it is possible that the allocated objcg pointer > array comes from the same slab that requires memory accounting. If this > happens, the slab will never become empty again as there is at least > one object left (the obj_cgroup array) in the slab. > > When it is freed, the objcg pointer array object may be the last one > in its slab and hence causes kfree() to be called again. With the > right workload, the slab cache may be set up in a way that allows the > recursive kfree() calling loop to nest deep enough to cause a kernel > stack overflow and panic the system. > > One way to solve this problem is to split the kmalloc-<n> caches > (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n> > (KMALLOC_NORMAL) caches for unaccounted objects only and a new set of > kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All > the other caches can still allow a mix of accounted and unaccounted > objects. > > With this change, all the objcg pointer array objects will come from > KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So > both the recursive kfree() problem and non-freeable slab problem are > gone. > > Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have > mixed accounted and unaccounted objects, this will slightly reduce the > number of objcg pointer arrays that need to be allocated and save a bit > of memory. On the other hand, creating a new set of kmalloc caches does > have the effect of reducing cache utilization. So it is properly a wash. > > The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and > KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches() > will include the newly added caches without change. > > Signed-off-by: Waiman Long <longman@redhat.com> > Suggested-by: Vlastimil Babka <vbabka@suse.cz> > Reviewed-by: Shakeel Butt <shakeelb@google.com> > Acked-by: Roman Gushchin <guro@fb.com> > --- > include/linux/slab.h | 42 +++++++++++++++++++++++++++++++++--------- > mm/slab_common.c | 25 +++++++++++++++++-------- > 2 files changed, 50 insertions(+), 17 deletions(-) The following are the diff's from previous version. It turns out that the previous patch doesn't work if CONFIG_ZONE_DMA isn't defined. diff --git a/include/linux/slab.h b/include/linux/slab.h index a51cad5f561c..aa7f6c222a60 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -312,16 +312,17 @@ static inline void __check_heap_object(const void *ptr, un signed long n, */ enum kmalloc_cache_type { KMALLOC_NORMAL = 0, -#ifdef CONFIG_MEMCG_KMEM - KMALLOC_CGROUP, -#else +#ifndef CONFIG_ZONE_DMA + KMALLOC_DMA = KMALLOC_NORMAL, +#endif +#ifndef CONFIG_MEMCG_KMEM KMALLOC_CGROUP = KMALLOC_NORMAL, +#else + KMALLOC_CGROUP, #endif KMALLOC_RECLAIM, #ifdef CONFIG_ZONE_DMA KMALLOC_DMA, -#else - KMALLOC_DMA = KMALLOC_NORMAL, #endif NR_KMALLOC_TYPES }; Cheers, Longman
WARNING: multiple messages have this Message-ID (diff)
From: Waiman Long <llong-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> To: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Vladimir Davydov <vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Christoph Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>, Pekka Enberg <penberg-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Joonsoo Kim <iamjoonsoo.kim-Hm3cg6mZ9cc@public.gmane.org>, Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org>, Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>, Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org Subject: Re: [PATCH v5 2/3] mm: memcg/slab: Create a new set of kmalloc-cg-<n> caches Date: Wed, 12 May 2021 10:54:19 -0400 [thread overview] Message-ID: <0919aaab-cc08-f86d-1f9a-8ddfeed7bb31@redhat.com> (raw) In-Reply-To: <20210512145107.6208-1-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> On 5/12/21 10:51 AM, Waiman Long wrote: > There are currently two problems in the way the objcg pointer array > (memcg_data) in the page structure is being allocated and freed. > > On its allocation, it is possible that the allocated objcg pointer > array comes from the same slab that requires memory accounting. If this > happens, the slab will never become empty again as there is at least > one object left (the obj_cgroup array) in the slab. > > When it is freed, the objcg pointer array object may be the last one > in its slab and hence causes kfree() to be called again. With the > right workload, the slab cache may be set up in a way that allows the > recursive kfree() calling loop to nest deep enough to cause a kernel > stack overflow and panic the system. > > One way to solve this problem is to split the kmalloc-<n> caches > (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n> > (KMALLOC_NORMAL) caches for unaccounted objects only and a new set of > kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All > the other caches can still allow a mix of accounted and unaccounted > objects. > > With this change, all the objcg pointer array objects will come from > KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So > both the recursive kfree() problem and non-freeable slab problem are > gone. > > Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have > mixed accounted and unaccounted objects, this will slightly reduce the > number of objcg pointer arrays that need to be allocated and save a bit > of memory. On the other hand, creating a new set of kmalloc caches does > have the effect of reducing cache utilization. So it is properly a wash. > > The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and > KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches() > will include the newly added caches without change. > > Signed-off-by: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> > Suggested-by: Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org> > Reviewed-by: Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> > Acked-by: Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org> > --- > include/linux/slab.h | 42 +++++++++++++++++++++++++++++++++--------- > mm/slab_common.c | 25 +++++++++++++++++-------- > 2 files changed, 50 insertions(+), 17 deletions(-) The following are the diff's from previous version. It turns out that the previous patch doesn't work if CONFIG_ZONE_DMA isn't defined. diff --git a/include/linux/slab.h b/include/linux/slab.h index a51cad5f561c..aa7f6c222a60 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -312,16 +312,17 @@ static inline void __check_heap_object(const void *ptr, un signed long n, */ enum kmalloc_cache_type { KMALLOC_NORMAL = 0, -#ifdef CONFIG_MEMCG_KMEM - KMALLOC_CGROUP, -#else +#ifndef CONFIG_ZONE_DMA + KMALLOC_DMA = KMALLOC_NORMAL, +#endif +#ifndef CONFIG_MEMCG_KMEM KMALLOC_CGROUP = KMALLOC_NORMAL, +#else + KMALLOC_CGROUP, #endif KMALLOC_RECLAIM, #ifdef CONFIG_ZONE_DMA KMALLOC_DMA, -#else - KMALLOC_DMA = KMALLOC_NORMAL, #endif NR_KMALLOC_TYPES }; Cheers, Longman
next prev parent reply other threads:[~2021-05-12 14:55 UTC|newest] Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-05 20:06 [PATCH v4 0/3] mm: memcg/slab: Fix objcg pointer array handling problem Waiman Long 2021-05-05 20:06 ` [PATCH v4 1/3] mm: memcg/slab: Properly set up gfp flags for objcg pointer array Waiman Long 2021-05-05 20:35 ` Roman Gushchin 2021-05-05 20:35 ` Roman Gushchin 2021-05-06 15:37 ` Vlastimil Babka 2021-05-06 15:37 ` Vlastimil Babka 2021-05-05 20:06 ` [PATCH v4 2/3] mm: memcg/slab: Create a new set of kmalloc-cg-<n> caches Waiman Long 2021-05-05 20:06 ` Waiman Long 2021-05-05 20:37 ` Roman Gushchin 2021-05-05 20:37 ` Roman Gushchin 2021-05-05 21:41 ` Vlastimil Babka 2021-05-05 23:19 ` Waiman Long 2021-05-05 23:19 ` Waiman Long 2021-05-06 16:00 ` Vlastimil Babka 2021-05-06 16:00 ` Vlastimil Babka 2021-05-06 16:07 ` Shakeel Butt 2021-05-06 16:07 ` Shakeel Butt 2021-05-06 16:07 ` Shakeel Butt 2021-05-06 19:30 ` Roman Gushchin 2021-05-06 19:30 ` Roman Gushchin 2021-05-07 18:45 ` Waiman Long 2021-05-07 18:45 ` Waiman Long 2021-05-05 20:06 ` [PATCH v4 3/3] mm: memcg/slab: Disable cache merging for KMALLOC_NORMAL caches Waiman Long 2021-05-05 20:06 ` Waiman Long 2021-05-05 20:38 ` Roman Gushchin 2021-05-05 20:38 ` Roman Gushchin 2021-05-05 20:39 ` Shakeel Butt 2021-05-05 20:39 ` Shakeel Butt 2021-05-05 20:39 ` Shakeel Butt 2021-05-06 16:02 ` Vlastimil Babka 2021-05-06 16:02 ` Vlastimil Babka 2021-05-12 14:51 ` [PATCH v5 2/3] mm: memcg/slab: Create a new set of kmalloc-cg-<n> caches Waiman Long 2021-05-12 14:51 ` Waiman Long 2021-05-12 14:54 ` Waiman Long [this message] 2021-05-12 14:54 ` Waiman Long 2021-05-13 0:32 ` Andrew Morton 2021-05-13 0:32 ` Andrew Morton 2021-05-13 8:40 ` Vlastimil Babka 2021-05-13 8:40 ` Vlastimil Babka 2021-05-13 16:22 ` Waiman Long 2021-05-13 16:22 ` Waiman Long
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