linux-kernel - Re: [PATCH v3 1/8] memcg: reduce memory size of mem_cgroup_events

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Date: Tue, 30 Apr 2024 10:29:31 -0700
From: "T.J. Mercier" <tjmercier@...gle.com>
To: Yosry Ahmed <yosryahmed@...gle.com>
Cc: Shakeel Butt <shakeel.butt@...ux.dev>, 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>, kernel-team@...a.com, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/8] memcg: reduce memory size of mem_cgroup_events_index

On Tue, Apr 30, 2024 at 1:34 AM Yosry Ahmed <yosryahmed@...gle.com> wrote:
>
> On Mon, Apr 29, 2024 at 11:06 PM Shakeel Butt <shakeel.butt@...uxdev> wrote:
> >
> > mem_cgroup_events_index is a translation table to get the right index of
> > the memcg relevant entry for the general vm_event_item. At the moment,
> > it is defined as integer array. However on a typical system the max
> > entry of vm_event_item (NR_VM_EVENT_ITEMS) is 113, so we don't need to
> > use int as storage type of the array. For now just use int8_t as type
> > and add a BUILD_BUG_ON() and will switch to short once NR_VM_EVENT_ITEMS
> > touches 127.
> >
> > Another benefit of this change is that the translation table fits in 2
> > cachelines while previously it would require 8 cachelines (assuming 64
> > bytes cachesline).
> >
> > Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
> > Reviewed-by: Roman Gushchin <roman.gushchin@...ux.dev>
>
> Reviewed-by: Yosry Ahmed <yosryahmed@...gle.com>
>
Reviewed-by: T.J. Mercier <tjmercier@...gle.com>