linux-kernel - Re: [RFC] mm/vmscan: add periodic slab shrinker

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Message-ID: <Ykyy8RfJgWDOGylv@casper.infradead.org>
Date:   Tue, 5 Apr 2022 22:21:53 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Yang Shi <shy828301@...il.com>
Cc:     Roman Gushchin <roman.gushchin@...ux.dev>,
        Dave Chinner <david@...morbit.com>,
        Hillf Danton <hdanton@...a.com>, MM <linux-mm@...ck.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Stephen Brennan <stephen.s.brennan@...cle.com>,
        Yu Zhao <yuzhao@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] mm/vmscan: add periodic slab shrinker

On Tue, Apr 05, 2022 at 01:58:59PM -0700, Yang Shi wrote:
> Yeah, I agree it actually doesn't make too much sense to return the
> number of reclaimed objects. Other part of vmscan returns the number
> of base pages, the sizes of slab objects are varied, it may be much
> smaller than a page, for example, dentry may be 192 bytes.

>From the point of view of vmscan, it only cares about the number of pages
freed because it's trying to free pages.  But from the point of view of
trying to keep the number of non-useful objects in check, the number of
objects freed is more important, and it doesn't matter whether we ended
up freeing any pages because we made memory available for this slab cache.