linux-kernel - Re: [PATCH] mm: slub: remove preemption disabling from put_cpu

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Message-ID: <CAMZfGtW=TXQQuu=f6ndoNUcaVe7O0SOGRV9J=Zf=Dz+MfMorog@mail.gmail.com>
Date:   Wed, 11 Aug 2021 22:49:06 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: slub: remove preemption disabling from put_cpu_partial

On Wed, Aug 11, 2021 at 8:40 PM Vlastimil Babka <vbabka@...e.cz> wrote:
>
> On 8/11/21 1:19 PM, Muchun Song wrote:
> > The commit d6e0b7fa1186 ("slub: make dead caches discard free slabs
> > immediately") introduced those logic to speed up the destruction of
> > per-memcg kmem caches, because kmem caches created for a memory
> > cgroup are only destroyed after the last page charged to the cgroup
> > is freed at that time. But since commit 9855609bde03 ("mm: memcg/slab:
> > use a single set of kmem_caches for all accounted allocations), we
> > do not have per-memcg kmem caches anymore. Are those code pointless?
> > No, the kmem_cache->cpu_partial can be set to zero by 'echo 0 > /sys/
> > kernel/slab/*/cpu_partial'. In this case, the slab page will be put
> > into cpu partial list and then moved to node list (because
> > slub_cpu_partial() returns zero). However, we can skip putting the
> > slab page to cpu partial list and just move it to node list directly.
> > We can adjust the condition of kmem_cache_has_cpu_partial() to
> > slub_cpu_partial() in __slab_free() and remove those code from
> > put_cpu_partial() for simplification.
> >
> > Signed-off-by: Muchun Song <songmuchun@...edance.com>
>
> Please check again current mmotm/next if this still applies, I think it
> shouldn't anymore. Thanks.
>

You are right. I didn't see it before. I guess it was merged
recently. But thanks for your reminder.