From: Johannes Weiner <hannes@cmpxchg.org> To: Wei Yang <richard.weiyang@gmail.com> Cc: mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, cgroups@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 2/3] mm/memcg: set pos to prev unconditionally Date: Tue, 29 Mar 2022 14:48:05 -0400 [thread overview] Message-ID: <YkNUZYrSHPjJ1XOb@cmpxchg.org> (raw) In-Reply-To: <20220225003437.12620-3-richard.weiyang@gmail.com> On Fri, Feb 25, 2022 at 12:34:36AM +0000, Wei Yang wrote: > Current code set pos to prev based on condition (prev && !reclaim), > while we can do this unconditionally. > > Since: > > * If !reclaim, pos is the same as prev no matter it is NULL or not. > * If reclaim, pos would be set properly from iter->position. > > Signed-off-by: Wei Yang <richard.weiyang@gmail.com> > --- > mm/memcontrol.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 9464fe2aa329..03399146168f 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -980,7 +980,7 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, > struct mem_cgroup_reclaim_iter *iter; > struct cgroup_subsys_state *css = NULL; > struct mem_cgroup *memcg = NULL; > - struct mem_cgroup *pos = NULL; > + struct mem_cgroup *pos = prev; I don't like this so much. It suggests pos always starts with prev, no matter what. But this isn't true for reclaim mode, which overrides the initialized value again. > if (mem_cgroup_disabled()) > return NULL; > @@ -988,9 +988,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, > if (!root) > root = root_mem_cgroup; > > - if (prev && !reclaim) > - pos = prev; How about making the reclaim vs non-reclaim mode explicit and do: if (reclaim) { ... pos = iter->position; ... } else { pos = prev; }
WARNING: multiple messages have this Message-ID (diff)
From: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org> To: Wei Yang <richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Cc: mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org Subject: Re: [PATCH 2/3] mm/memcg: set pos to prev unconditionally Date: Tue, 29 Mar 2022 14:48:05 -0400 [thread overview] Message-ID: <YkNUZYrSHPjJ1XOb@cmpxchg.org> (raw) In-Reply-To: <20220225003437.12620-3-richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> On Fri, Feb 25, 2022 at 12:34:36AM +0000, Wei Yang wrote: > Current code set pos to prev based on condition (prev && !reclaim), > while we can do this unconditionally. > > Since: > > * If !reclaim, pos is the same as prev no matter it is NULL or not. > * If reclaim, pos would be set properly from iter->position. > > Signed-off-by: Wei Yang <richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> > --- > mm/memcontrol.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 9464fe2aa329..03399146168f 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -980,7 +980,7 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, > struct mem_cgroup_reclaim_iter *iter; > struct cgroup_subsys_state *css = NULL; > struct mem_cgroup *memcg = NULL; > - struct mem_cgroup *pos = NULL; > + struct mem_cgroup *pos = prev; I don't like this so much. It suggests pos always starts with prev, no matter what. But this isn't true for reclaim mode, which overrides the initialized value again. > if (mem_cgroup_disabled()) > return NULL; > @@ -988,9 +988,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, > if (!root) > root = root_mem_cgroup; > > - if (prev && !reclaim) > - pos = prev; How about making the reclaim vs non-reclaim mode explicit and do: if (reclaim) { ... pos = iter->position; ... } else { pos = prev; }
next prev parent reply other threads:[~2022-03-29 18:48 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-02-25 0:34 [PATCH 0/3] mm/memcg: some cleanup for mem_cgroup_iter() Wei Yang 2022-02-25 0:34 ` Wei Yang 2022-02-25 0:34 ` [PATCH 1/3] mm/memcg: set memcg after css verified and got reference Wei Yang 2022-02-25 0:34 ` Wei Yang 2022-03-29 18:44 ` Johannes Weiner 2022-03-29 18:44 ` Johannes Weiner 2022-02-25 0:34 ` [PATCH 2/3] mm/memcg: set pos to prev unconditionally Wei Yang 2022-02-25 0:34 ` Wei Yang 2022-03-29 18:48 ` Johannes Weiner [this message] 2022-03-29 18:48 ` Johannes Weiner 2022-03-30 0:47 ` Wei Yang 2022-03-30 0:47 ` Wei Yang 2022-03-30 12:08 ` Johannes Weiner 2022-03-30 12:08 ` Johannes Weiner 2022-03-30 14:22 ` Wei Yang 2022-03-30 14:22 ` Wei Yang 2022-02-25 0:34 ` [PATCH 3/3] mm/memcg: move generation assignment and comparison together Wei Yang 2022-02-25 0:34 ` Wei Yang 2022-03-30 15:57 ` Johannes Weiner 2022-03-30 15:57 ` Johannes Weiner 2022-03-30 23:04 ` Wei Yang 2022-03-30 23:04 ` Wei Yang 2022-02-25 8:13 ` [PATCH 0/3] mm/memcg: some cleanup for mem_cgroup_iter() Michal Hocko 2022-02-25 8:13 ` Michal Hocko
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