linux-kernel - Re: [PATCH v2 3/7] memcg: reduce memory for the lruvec and memcg stats

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Message-ID: <uewheydidpkiqywtc4m6dcmvlfj7raocpngtbqocksxvf4nyz4@srxnazpqxvzy>
Date: Fri, 26 Apr 2024 18:16:32 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Yosry Ahmed <yosryahmed@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Muchun Song <muchun.song@...ux.dev>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/7] memcg: reduce memory for the lruvec and memcg
 stats

On Fri, Apr 26, 2024 at 05:51:23PM -0700, Yosry Ahmed wrote:
> On Fri, Apr 26, 2024 at 5:37 PM Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> >
> > At the moment, the amount of memory allocated for stats related structs
> > in the mem_cgroup corresponds to the size of enum node_stat_item.
> > However not all fields in enum node_stat_item has corresponding memcg
> > stats. So, let's use indirection mechanism similar to the one used for
> > memcg vmstats management.
> 
> Just curious, does the indirection table cause any noticeable
> performance impact? My guess is no, but the update paths are usually
> very performance sensitive.
> 
> I guess lkp will shout at us if there are any noticeable regressions.

Yeah and that is the reason I made the indirection table smaller (i.e.
int8_t) to keep more entries in a single cacheline.