From: Michal Hocko <mhocko@suse.com> To: Waiman Long <longman@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org>, Vladimir Davydov <vdavydov.dev@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, Tejun Heo <tj@kernel.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>, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Shakeel Butt <shakeelb@google.com>, Muchun Song <songmuchun@bytedance.com>, Alex Shi <alex.shi@linux.alibaba.com>, Chris Down <chris@chrisdown.name>, Yafang Shao <laoar.shao@gmail.com>, Wei Yang <richard.weiyang@gmail.com>, Masayoshi Mizuma <msys.mizuma@gmail.com>, Xing Zhengjun <zhengjun.xing@linux.intel.com>, Matthew Wilcox <willy@infradead.org> Subject: Re: [PATCH] mm/memcg: Fix incorrect flushing of lruvec data in obj_stock Date: Mon, 2 Aug 2021 08:28:13 +0200 [thread overview] Message-ID: <YQeQfX3t8k+U3MIL@dhcp22.suse.cz> (raw) In-Reply-To: <20210802022827.10192-1-longman@redhat.com> On Sun 01-08-21 22:28:27, Waiman Long wrote: > When mod_objcg_state() is called with a pgdat that is different from > that in the obj_stock, the old lruvec data cached in obj_stock are > flushed out. Unfortunately, they were flushed to the new pgdat and > hence the wrong node, not the one cached in obj_stock. It would be great to explicitly mention user observable problems here. I do assume this will make slab stats skewed but the effect wouldn't be very big, right? > Fix that by flushing the data to the cached pgdat instead. > > Fixes: 68ac5b3c8db2 ("mm/memcg: cache vmstat data in percpu memcg_stock_pcp") > Signed-off-by: Waiman Long <longman@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/memcontrol.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index ae1f5d0cb581..881ec4ddddcd 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3106,17 +3106,19 @@ void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, > stock->cached_pgdat = pgdat; > } else if (stock->cached_pgdat != pgdat) { > /* Flush the existing cached vmstat data */ > + struct pglist_data *oldpg = stock->cached_pgdat; > + > + stock->cached_pgdat = pgdat; > if (stock->nr_slab_reclaimable_b) { > - mod_objcg_mlstate(objcg, pgdat, NR_SLAB_RECLAIMABLE_B, > + mod_objcg_mlstate(objcg, oldpg, NR_SLAB_RECLAIMABLE_B, > stock->nr_slab_reclaimable_b); > stock->nr_slab_reclaimable_b = 0; > } > if (stock->nr_slab_unreclaimable_b) { > - mod_objcg_mlstate(objcg, pgdat, NR_SLAB_UNRECLAIMABLE_B, > + mod_objcg_mlstate(objcg, oldpg, NR_SLAB_UNRECLAIMABLE_B, > stock->nr_slab_unreclaimable_b); > stock->nr_slab_unreclaimable_b = 0; > } > - stock->cached_pgdat = pgdat; Minor nit. Is there any reason to move the cached_pgdat? TBH I found the original way better from the readability POV. > } > > bytes = (idx == NR_SLAB_RECLAIMABLE_B) ? &stock->nr_slab_reclaimable_b > -- > 2.18.1 -- Michal Hocko SUSE Labs
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org> To: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Vladimir Davydov <vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@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>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Muchun Song <songmuchun-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>, Alex Shi <alex.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>, Chris Down <chris-6Bi1550iOqEnzZ6mRAm98g@public.gmane.org>, Yafang Shao <laoar.shao-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Wei Yang <richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Masayoshi Mizuma <msys.mizuma-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Xing Zhengjun <zhengjun.xing-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>, Matthew Subject: Re: [PATCH] mm/memcg: Fix incorrect flushing of lruvec data in obj_stock Date: Mon, 2 Aug 2021 08:28:13 +0200 [thread overview] Message-ID: <YQeQfX3t8k+U3MIL@dhcp22.suse.cz> (raw) In-Reply-To: <20210802022827.10192-1-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> On Sun 01-08-21 22:28:27, Waiman Long wrote: > When mod_objcg_state() is called with a pgdat that is different from > that in the obj_stock, the old lruvec data cached in obj_stock are > flushed out. Unfortunately, they were flushed to the new pgdat and > hence the wrong node, not the one cached in obj_stock. It would be great to explicitly mention user observable problems here. I do assume this will make slab stats skewed but the effect wouldn't be very big, right? > Fix that by flushing the data to the cached pgdat instead. > > Fixes: 68ac5b3c8db2 ("mm/memcg: cache vmstat data in percpu memcg_stock_pcp") > Signed-off-by: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Acked-by: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org> > --- > mm/memcontrol.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index ae1f5d0cb581..881ec4ddddcd 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3106,17 +3106,19 @@ void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat, > stock->cached_pgdat = pgdat; > } else if (stock->cached_pgdat != pgdat) { > /* Flush the existing cached vmstat data */ > + struct pglist_data *oldpg = stock->cached_pgdat; > + > + stock->cached_pgdat = pgdat; > if (stock->nr_slab_reclaimable_b) { > - mod_objcg_mlstate(objcg, pgdat, NR_SLAB_RECLAIMABLE_B, > + mod_objcg_mlstate(objcg, oldpg, NR_SLAB_RECLAIMABLE_B, > stock->nr_slab_reclaimable_b); > stock->nr_slab_reclaimable_b = 0; > } > if (stock->nr_slab_unreclaimable_b) { > - mod_objcg_mlstate(objcg, pgdat, NR_SLAB_UNRECLAIMABLE_B, > + mod_objcg_mlstate(objcg, oldpg, NR_SLAB_UNRECLAIMABLE_B, > stock->nr_slab_unreclaimable_b); > stock->nr_slab_unreclaimable_b = 0; > } > - stock->cached_pgdat = pgdat; Minor nit. Is there any reason to move the cached_pgdat? TBH I found the original way better from the readability POV. > } > > bytes = (idx == NR_SLAB_RECLAIMABLE_B) ? &stock->nr_slab_reclaimable_b > -- > 2.18.1 -- Michal Hocko SUSE Labs
next prev parent reply other threads:[~2021-08-02 6:28 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-02 2:28 [PATCH] mm/memcg: Fix incorrect flushing of lruvec data in obj_stock Waiman Long 2021-08-02 2:28 ` Waiman Long 2021-08-02 6:28 ` Michal Hocko [this message] 2021-08-02 6:28 ` Michal Hocko 2021-08-02 13:32 ` Waiman Long 2021-08-02 13:32 ` Waiman Long 2021-08-02 14:32 ` Shakeel Butt 2021-08-02 14:32 ` Shakeel Butt 2021-08-02 14:32 ` Shakeel Butt
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