linux-kernel - Re: [PATCH v4 03/19] mm: memcg: convert vmstat slab counters to bytes

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Message-ID: <20200527162509.GA396660@carbon.dhcp.thefacebook.com>
Date:   Wed, 27 May 2020 09:25:09 -0700
From:   Roman Gushchin <guro@...com>
To:     Vlastimil Babka <vbabka@...e.cz>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>, <linux-mm@...ck.org>,
        <kernel-team@...com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 03/19] mm: memcg: convert vmstat slab counters to bytes

On Wed, May 27, 2020 at 01:43:16PM +0200, Vlastimil Babka wrote:
> On 5/26/20 11:42 PM, Roman Gushchin wrote:
> > In order to prepare for per-object slab memory accounting, convert
> > NR_SLAB_RECLAIMABLE and NR_SLAB_UNRECLAIMABLE vmstat items to bytes.
> > 
> > To make it obvious, rename them to NR_SLAB_RECLAIMABLE_B and
> > NR_SLAB_UNRECLAIMABLE_B (similar to NR_KERNEL_STACK_KB).
> > 
> > Internally global and per-node counters are stored in pages,
> > however memcg and lruvec counters are stored in bytes.
> > This scheme may look weird, but only for now. As soon as slab
> > pages will be shared between multiple cgroups, global and
> > node counters will reflect the total number of slab pages.
> > However memcg and lruvec counters will be used for per-memcg
> > slab memory tracking, which will take separate kernel objects
> > in the account. Keeping global and node counters in pages helps
> > to avoid additional overhead.
> > 
> > The size of slab memory shouldn't exceed 4Gb on 32-bit machines,
> > so it will fit into atomic_long_t we use for vmstats.
> > 
> > Signed-off-by: Roman Gushchin <guro@...com>
> 
> You didn't add Acked-by: Johannes Weiner <hannes@...xchg.org>
> ( see 20200507204137.GC161043@...xchg.org )

Indeed.

> (Noticed thanks to the great 'b4 am' and 'git range-diff' tools)

I'll check them, thanks!

> 
> Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
> 

Thank you!