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[73.93.239.127]) by smtp.gmail.com with ESMTPSA id 124sm3498648pfd.59.2021.01.27.15.34.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Jan 2021 15:34:05 -0800 (PST) From: Yang Shi To: guro@fb.com, ktkhai@virtuozzo.com, shakeelb@google.com, david@fromorbit.com, hannes@cmpxchg.org, mhocko@suse.com, akpm@linux-foundation.org Cc: shy828301@gmail.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [v5 PATCH 07/11] mm: vmscan: add per memcg shrinker nr_deferred Date: Wed, 27 Jan 2021 15:33:41 -0800 Message-Id: <20210127233345.339910-8-shy828301@gmail.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210127233345.339910-1-shy828301@gmail.com> References: <20210127233345.339910-1-shy828301@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Currently the number of deferred objects are per shrinker, but some slabs= , for example, vfs inode/dentry cache are per memcg, this would result in poor isolation= among memcgs. The deferred objects typically are generated by __GFP_NOFS allocations, o= ne memcg with excessive __GFP_NOFS allocations may blow up deferred objects, then other= innocent memcgs may suffer from over shrink, excessive reclaim latency, etc. For example, two workloads run in memcgA and memcgB respectively, workloa= d in B is vfs heavy workload. Workload in A generates excessive deferred objects, then= B's vfs cache might be hit heavily (drop half of caches) by B's limit reclaim or global= reclaim. We observed this hit in our production environment which was running vfs = heavy workload shown as the below tracing log: <...>-409454 [016] .... 28286961.747146: mm_shrink_slab_start: super_cach= e_scan+0x0/0x1a0 ffff9a83046f3458: nid: 1 objects to shrink 3641681686040 gfp_flags GFP_HIGHUSER_MOVABLE|__G= FP_ZERO pgs_scanned 1 lru_pgs 15721 cache items 246404277 delta 31345 total_scan 123202138 <...>-409454 [022] .... 28287105.928018: mm_shrink_slab_end: super_cache_= scan+0x0/0x1a0 ffff9a83046f3458: nid: 1 unused scan count 3641681686040 new scan count 3641798379189 total= _scan 602 last shrinker return val 123186855 The vfs cache and page cache ration was 10:1 on this machine, and half of= caches were dropped. This also resulted in significant amount of page caches were dropped due = to inodes eviction. Make nr_deferred per memcg for memcg aware shrinkers would solve the unfa= irness and bring better isolation. When memcg is not enabled (!CONFIG_MEMCG or memcg disabled), the shrinker= 's nr_deferred would be used. And non memcg aware shrinkers use shrinker's nr_deferred = all the time. Signed-off-by: Yang Shi --- include/linux/memcontrol.h | 7 +++--- mm/vmscan.c | 48 +++++++++++++++++++++++++------------- 2 files changed, 36 insertions(+), 19 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 62b888b88a5f..e0384367e07d 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -93,12 +93,13 @@ struct lruvec_stat { }; =20 /* - * Bitmap of shrinker::id corresponding to memcg-aware shrinkers, - * which have elements charged to this memcg. + * Bitmap and deferred work of shrinker::id corresponding to memcg-aware + * shrinkers, which have elements charged to this memcg. */ struct shrinker_info { struct rcu_head rcu; - unsigned long map[]; + unsigned long *map; + atomic_long_t *nr_deferred; }; =20 /* diff --git a/mm/vmscan.c b/mm/vmscan.c index 256896d157d4..20be0db291fe 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -187,16 +187,21 @@ static DECLARE_RWSEM(shrinker_rwsem); #ifdef CONFIG_MEMCG static int shrinker_nr_max; =20 +#define NR_MAX_TO_SHR_MAP_SIZE(nr_max) \ + ((nr_max / BITS_PER_LONG + 1) * sizeof(unsigned long)) + static void free_shrinker_info_rcu(struct rcu_head *head) { kvfree(container_of(head, struct shrinker_info, rcu)); } =20 static int expand_one_shrinker_info(struct mem_cgroup *memcg, - int size, int old_size) + int m_size, int d_size, + int old_m_size, int old_d_size) { struct shrinker_info *new, *old; int nid; + int size =3D m_size + d_size; =20 for_each_node(nid) { old =3D rcu_dereference_protected( @@ -209,9 +214,15 @@ static int expand_one_shrinker_info(struct mem_cgrou= p *memcg, if (!new) return -ENOMEM; =20 - /* Set all old bits, clear all new bits */ - memset(new->map, (int)0xff, old_size); - memset((void *)new->map + old_size, 0, size - old_size); + new->map =3D (unsigned long *)(new + 1); + new->nr_deferred =3D (void *)new->map + m_size; + + /* map: set all old bits, clear all new bits */ + memset(new->map, (int)0xff, old_m_size); + memset((void *)new->map + old_m_size, 0, m_size - old_m_size); + /* nr_deferred: copy old values, clear all new values */ + memcpy(new->nr_deferred, old->nr_deferred, old_d_size); + memset((void *)new->nr_deferred + old_d_size, 0, d_size - old_d_size); =20 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, new); call_rcu(&old->rcu, free_shrinker_info_rcu); @@ -226,9 +237,6 @@ void free_shrinker_info(struct mem_cgroup *memcg) struct shrinker_info *info; int nid; =20 - if (mem_cgroup_is_root(memcg)) - return; - for_each_node(nid) { pn =3D mem_cgroup_nodeinfo(memcg, nid); info =3D rcu_dereference_protected(pn->shrinker_info, true); @@ -242,12 +250,13 @@ int alloc_shrinker_info(struct mem_cgroup *memcg) { struct shrinker_info *info; int nid, size, ret =3D 0; - - if (mem_cgroup_is_root(memcg)) - return 0; + int m_size, d_size =3D 0; =20 down_write(&shrinker_rwsem); - size =3D (shrinker_nr_max / BITS_PER_LONG + 1) * sizeof(unsigned long); + m_size =3D NR_MAX_TO_SHR_MAP_SIZE(shrinker_nr_max); + d_size =3D shrinker_nr_max * sizeof(atomic_long_t); + size =3D m_size + d_size; + for_each_node(nid) { info =3D kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid); if (!info) { @@ -255,6 +264,8 @@ int alloc_shrinker_info(struct mem_cgroup *memcg) ret =3D -ENOMEM; break; } + info->map =3D (unsigned long *)(info + 1); + info->nr_deferred =3D (void *)info->map + m_size; rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info); } up_write(&shrinker_rwsem); @@ -266,10 +277,16 @@ static int expand_shrinker_info(int new_id) { int size, old_size, ret =3D 0; int new_nr_max =3D new_id + 1; + int m_size, d_size =3D 0; + int old_m_size, old_d_size =3D 0; struct mem_cgroup *memcg; =20 - size =3D (new_nr_max / BITS_PER_LONG + 1) * sizeof(unsigned long); - old_size =3D (shrinker_nr_max / BITS_PER_LONG + 1) * sizeof(unsigned lo= ng); + m_size =3D NR_MAX_TO_SHR_MAP_SIZE(new_nr_max); + d_size =3D new_nr_max * sizeof(atomic_long_t); + size =3D m_size + d_size; + old_m_size =3D NR_MAX_TO_SHR_MAP_SIZE(shrinker_nr_max); + old_d_size =3D shrinker_nr_max * sizeof(atomic_long_t); + old_size =3D old_m_size + old_d_size; if (size <=3D old_size) goto out; =20 @@ -278,9 +295,8 @@ static int expand_shrinker_info(int new_id) =20 memcg =3D mem_cgroup_iter(NULL, NULL, NULL); do { - if (mem_cgroup_is_root(memcg)) - continue; - ret =3D expand_one_shrinker_info(memcg, size, old_size); + ret =3D expand_one_shrinker_info(memcg, m_size, d_size, + old_m_size, old_d_size); if (ret) { mem_cgroup_iter_break(NULL, memcg); goto out; --=20 2.26.2