Re: [PATCH v7 08/19] mm: memcg/slab: save obj_cgroup for non-root slab objects

From: Naresh Kamboju
Date: Thu Jul 16 2020 - 12:55:17 EST

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On Tue, 23 Jun 2020 at 23:11, Roman Gushchin <guro@xxxxxx> wrote:
>
> Store the obj_cgroup pointer in the corresponding place of
> page->obj_cgroups for each allocated non-root slab object. Make sure that
> each allocated object holds a reference to obj_cgroup.
>
> Objcg pointer is obtained from the memcg->objcg dereferencing in
> memcg_kmem_get_cache() and passed from pre_alloc_hook to post_alloc_hook.
> Then in case of successful allocation(s) it's getting stored in the
> page->obj_cgroups vector.
>
> The objcg obtaining part look a bit bulky now, but it will be simplified
> by next commits in the series.
>
> Signed-off-by: Roman Gushchin <guro@xxxxxx>
> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
> ---
> include/linux/memcontrol.h | 3 +-
> mm/memcontrol.c | 14 +++++++--
> mm/slab.c | 18 +++++++-----
> mm/slab.h | 60 ++++++++++++++++++++++++++++++++++----
> mm/slub.c | 14 +++++----
> 5 files changed, 88 insertions(+), 21 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index f2f9d5d6b7d1..b845e908e76e 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1404,7 +1404,8 @@ static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
> }
> #endif
>
> -struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep);
> +struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep,
> + struct obj_cgroup **objcgp);
> void memcg_kmem_put_cache(struct kmem_cache *cachep);
>
> #ifdef CONFIG_MEMCG_KMEM
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 60e3f3ca75ca..5e55c7afc18c 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2973,7 +2973,8 @@ static inline bool memcg_kmem_bypass(void)
> * done with it, memcg_kmem_put_cache() must be called to release the
> * reference.
> */
> -struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep)
> +struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep,
> + struct obj_cgroup **objcgp)
> {
> struct mem_cgroup *memcg;
> struct kmem_cache *memcg_cachep;
> @@ -3029,8 +3030,17 @@ struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep)
> */
> if (unlikely(!memcg_cachep))
> memcg_schedule_kmem_cache_create(memcg, cachep);
> - else if (percpu_ref_tryget(&memcg_cachep->memcg_params.refcnt))
> + else if (percpu_ref_tryget(&memcg_cachep->memcg_params.refcnt)) {
> + struct obj_cgroup *objcg = rcu_dereference(memcg->objcg);
> +
> + if (!objcg || !obj_cgroup_tryget(objcg)) {
> + percpu_ref_put(&memcg_cachep->memcg_params.refcnt);
> + goto out_unlock;
> + }
> +
> + *objcgp = objcg;
> cachep = memcg_cachep;
> + }
> out_unlock:
> rcu_read_unlock();
> return cachep;
> diff --git a/mm/slab.c b/mm/slab.c
> index 4c7013eeacd9..a7cc1336221f 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3222,9 +3222,10 @@ slab_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
> unsigned long save_flags;
> void *ptr;
> int slab_node = numa_mem_id();
> + struct obj_cgroup *objcg = NULL;
>
> flags &= gfp_allowed_mask;
> - cachep = slab_pre_alloc_hook(cachep, flags);
> + cachep = slab_pre_alloc_hook(cachep, &objcg, 1, flags);
> if (unlikely(!cachep))
> return NULL;
>
> @@ -3260,7 +3261,7 @@ slab_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
> if (unlikely(slab_want_init_on_alloc(flags, cachep)) && ptr)
> memset(ptr, 0, cachep->object_size);
>
> - slab_post_alloc_hook(cachep, flags, 1, &ptr);
> + slab_post_alloc_hook(cachep, objcg, flags, 1, &ptr);
> return ptr;
> }
>
> @@ -3301,9 +3302,10 @@ slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller)
> {
> unsigned long save_flags;
> void *objp;
> + struct obj_cgroup *objcg = NULL;
>
> flags &= gfp_allowed_mask;
> - cachep = slab_pre_alloc_hook(cachep, flags);
> + cachep = slab_pre_alloc_hook(cachep, &objcg, 1, flags);
> if (unlikely(!cachep))
> return NULL;
>
> @@ -3317,7 +3319,7 @@ slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller)
> if (unlikely(slab_want_init_on_alloc(flags, cachep)) && objp)
> memset(objp, 0, cachep->object_size);
>
> - slab_post_alloc_hook(cachep, flags, 1, &objp);
> + slab_post_alloc_hook(cachep, objcg, flags, 1, &objp);
> return objp;
> }
>
> @@ -3443,6 +3445,7 @@ void ___cache_free(struct kmem_cache *cachep, void *objp,
> memset(objp, 0, cachep->object_size);
> kmemleak_free_recursive(objp, cachep->flags);
> objp = cache_free_debugcheck(cachep, objp, caller);
> + memcg_slab_free_hook(cachep, virt_to_head_page(objp), objp);
>
> /*
> * Skip calling cache_free_alien() when the platform is not numa.
> @@ -3508,8 +3511,9 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
> void **p)
> {
> size_t i;
> + struct obj_cgroup *objcg = NULL;
>
> - s = slab_pre_alloc_hook(s, flags);
> + s = slab_pre_alloc_hook(s, &objcg, size, flags);
> if (!s)
> return 0;
>
> @@ -3532,13 +3536,13 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
> for (i = 0; i < size; i++)
> memset(p[i], 0, s->object_size);
>
> - slab_post_alloc_hook(s, flags, size, p);
> + slab_post_alloc_hook(s, objcg, flags, size, p);
> /* FIXME: Trace call missing. Christoph would like a bulk variant */
> return size;
> error:
> local_irq_enable();
> cache_alloc_debugcheck_after_bulk(s, flags, i, p, _RET_IP_);
> - slab_post_alloc_hook(s, flags, i, p);
> + slab_post_alloc_hook(s, objcg, flags, i, p);
> __kmem_cache_free_bulk(s, i, p);
> return 0;
> }
> diff --git a/mm/slab.h b/mm/slab.h
> index 7d175c2f1a61..c37a50f26e41 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -469,6 +469,41 @@ static inline void memcg_free_page_obj_cgroups(struct page *page)
> page->obj_cgroups = NULL;
> }
>
> +static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
> + struct obj_cgroup *objcg,
> + size_t size, void **p)
> +{
> + struct page *page;
> + unsigned long off;
> + size_t i;
> +
> + for (i = 0; i < size; i++) {
> + if (likely(p[i])) {
> + page = virt_to_head_page(p[i]);
> + off = obj_to_index(s, page, p[i]);
> + obj_cgroup_get(objcg);
> + page_obj_cgroups(page)[off] = objcg;
> + }
> + }
> + obj_cgroup_put(objcg);
> + memcg_kmem_put_cache(s);
> +}
> +
> +static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
> + void *p)
> +{
> + struct obj_cgroup *objcg;
> + unsigned int off;
> +
> + if (!memcg_kmem_enabled() || is_root_cache(s))
> + return;
> +
> + off = obj_to_index(s, page, p);
> + objcg = page_obj_cgroups(page)[off];
> + page_obj_cgroups(page)[off] = NULL;
> + obj_cgroup_put(objcg);
> +}
> +
> extern void slab_init_memcg_params(struct kmem_cache *);
> extern void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg);
>
> @@ -528,6 +563,17 @@ static inline void memcg_free_page_obj_cgroups(struct page *page)
> {
> }
>
> +static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
> + struct obj_cgroup *objcg,
> + size_t size, void **p)
> +{
> +}
> +
> +static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
> + void *p)
> +{
> +}
> +
> static inline void slab_init_memcg_params(struct kmem_cache *s)
> {
> }
> @@ -630,7 +676,8 @@ static inline size_t slab_ksize(const struct kmem_cache *s)
> }
>
> static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s,
> - gfp_t flags)
> + struct obj_cgroup **objcgp,
> + size_t size, gfp_t flags)
> {
> flags &= gfp_allowed_mask;
>
> @@ -644,13 +691,14 @@ static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s,
>
> if (memcg_kmem_enabled() &&
> ((flags & __GFP_ACCOUNT) || (s->flags & SLAB_ACCOUNT)))
> - return memcg_kmem_get_cache(s);
> + return memcg_kmem_get_cache(s, objcgp);
>
> return s;
> }
>
> -static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
> - size_t size, void **p)
> +static inline void slab_post_alloc_hook(struct kmem_cache *s,
> + struct obj_cgroup *objcg,
> + gfp_t flags, size_t size, void **p)
> {
> size_t i;
>
> @@ -662,8 +710,8 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
> s->flags, flags);
> }
>
> - if (memcg_kmem_enabled())
> - memcg_kmem_put_cache(s);
> + if (memcg_kmem_enabled() && !is_root_cache(s))
> + memcg_slab_post_alloc_hook(s, objcg, size, p);
> }
>
> #ifndef CONFIG_SLOB
> diff --git a/mm/slub.c b/mm/slub.c
> index aa8d18824e62..25810980a26c 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2821,8 +2821,9 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
> struct kmem_cache_cpu *c;
> struct page *page;
> unsigned long tid;
> + struct obj_cgroup *objcg = NULL;
>
> - s = slab_pre_alloc_hook(s, gfpflags);
> + s = slab_pre_alloc_hook(s, &objcg, 1, gfpflags);
> if (!s)
> return NULL;
> redo:
> @@ -2898,7 +2899,7 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
> if (unlikely(slab_want_init_on_alloc(gfpflags, s)) && object)
> memset(object, 0, s->object_size);
>
> - slab_post_alloc_hook(s, gfpflags, 1, &object);
> + slab_post_alloc_hook(s, objcg, gfpflags, 1, &object);
>
> return object;
> }
> @@ -3103,6 +3104,8 @@ static __always_inline void do_slab_free(struct kmem_cache *s,
> void *tail_obj = tail ? : head;
> struct kmem_cache_cpu *c;
> unsigned long tid;
> +
> + memcg_slab_free_hook(s, page, head);
> redo:
> /*
> * Determine the currently cpus per cpu slab.
> @@ -3282,9 +3285,10 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
> {
> struct kmem_cache_cpu *c;
> int i;
> + struct obj_cgroup *objcg = NULL;
>
> /* memcg and kmem_cache debug support */
> - s = slab_pre_alloc_hook(s, flags);
> + s = slab_pre_alloc_hook(s, &objcg, size, flags);
> if (unlikely(!s))
> return false;
> /*
> @@ -3338,11 +3342,11 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
> }
>
> /* memcg and kmem_cache debug support */
> - slab_post_alloc_hook(s, flags, size, p);
> + slab_post_alloc_hook(s, objcg, flags, size, p);
> return i;
> error:
> local_irq_enable();
> - slab_post_alloc_hook(s, flags, i, p);
> + slab_post_alloc_hook(s, objcg, flags, i, p);
> __kmem_cache_free_bulk(s, i, p);
> return 0;
> }
>

I am not sure if this is the related patch or not that is causing
mips architecture build failure on linux -next.

make -sk KBUILD_BUILD_USER=TuxBuild -C/linux -j16 ARCH=mips
CROSS_COMPILE=mips-linux-gnu- HOSTCC=gcc CC="sccache
mips-linux-gnu-gcc" O=build
#
../mm/slub.c: In function âslab_alloc.constpropâ:
../mm/slub.c:2897:30: error: inlining failed in call to always_inline
âslab_alloc.constpropâ: recursive inlining
2897 | static __always_inline void *slab_alloc(struct kmem_cache *s,
| ^~~~~~~~~~
../mm/slub.c:2905:14: note: called from here
2905 | void *ret = slab_alloc(s, gfpflags, _RET_IP_);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../mm/slub.c: In function âsysfs_slab_aliasâ:
../mm/slub.c:2897:30: error: inlining failed in call to always_inline
âslab_alloc.constpropâ: recursive inlining
2897 | static __always_inline void *slab_alloc(struct kmem_cache *s,
| ^~~~~~~~~~
../mm/slub.c:2905:14: note: called from here
2905 | void *ret = slab_alloc(s, gfpflags, _RET_IP_);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../mm/slub.c: In function âsysfs_slab_addâ:
../mm/slub.c:2897:30: error: inlining failed in call to always_inline
âslab_alloc.constpropâ: recursive inlining
2897 | static __always_inline void *slab_alloc(struct kmem_cache *s,
| ^~~~~~~~~~
../mm/slub.c:2905:14: note: called from here
2905 | void *ret = slab_alloc(s, gfpflags, _RET_IP_);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Full build log link,
https://builds.tuxbuild.com/jBgeEp1SD-bUldWES782yQ/build.log

--
Linaro LKFT
https://lkft.linaro.org

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