Re: [4.13-rc1] /proc/meminfo reports that Slab: is little used.

[Johannes Weiner <hannes@cmpxchg.org>]

On Fri, Jul 28, 2017 at 11:07:51AM +0200, Michal Hocko wrote:
> On Thu 27-07-17 12:23:55, Johannes Weiner wrote:
> > >From 14e3d7647b3cf524dbb005faaea96b00b6909c12 Mon Sep 17 00:00:00 2001
> > From: Johannes Weiner <hannes@cmpxchg.org>
> > Date: Thu, 27 Jul 2017 11:59:38 -0400
> > Subject: [PATCH] mm: fix global NR_SLAB_.*CLAIMABLE counter reads
> > 
> > As Tetsuo points out:
> > 
> >     Commit 385386cff4c6f047 ("mm: vmstat: move slab statistics from
> >     zone to node counters") broke "Slab:" field of /proc/meminfo . It
> >     shows nearly 0kB.
> > 
> > In addition to /proc/meminfo, this problem also affects the slab
> > counters OOM/allocation failure info dumps, can cause early -ENOMEM
> > from overcommit protection, and miscalculate image size requirements
> > during suspend-to-disk.
> > 
> > This is because the patch in question switched the slab counters from
> > the zone level to the node level, but forgot to update the global
> > accessor functions to read the aggregate node data instead of the
> > aggregate zone data.
> > 
> > Use global_node_page_state() to access the global slab counters.
> > 
> > Fixes: 385386cff4c6 ("mm: vmstat: move slab statistics from zone to node counters")
> > Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> 
> Looks good to me
> 
> Acked-by: Michal Hocko <mhocko@suse.com>

Thanks

> From: Michal Hocko <mhocko@suse.com>
> Date: Fri, 28 Jul 2017 11:02:51 +0200
> Subject: [PATCH] mm: rename global_page_state to global_zone_page_state
> 
> global_page_state is error prone as a recent bug report pointed out [1].
> It only returns proper values for zone based counters as the enum it
> gets suggests. We already have global_node_page_state so let's rename
> global_page_state to global_zone_page_state to be more explicit here.
> All existing users seems to be correct
> $ git grep "global_page_state(NR_" | sed 's@.*(\(NR_[A-Z_]*\)).*@\1@' | sort | uniq -c
>       2 NR_BOUNCE
>       2 NR_FREE_CMA_PAGES
>      11 NR_FREE_PAGES
>       1 NR_KERNEL_STACK_KB
>       1 NR_MLOCK
>       2 NR_PAGETABLE
> 
> This patch shouldn't introduce any functional change.
> 
> [1] http://lkml.kernel.org/r/201707260628.v6Q6SmaS030814@www262.sakura.ne.jp
> 
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Yeah I think that's a good idea. I suspect Mel wanted to keep churn in
unrelated callsites down when he introduced the node stuff, since that
was already a big patch series. It makes sense to clean this up now.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

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