linux-kernel - Re: [RFC PATCH v3 0/7] slub: Delay freezing of CPU partial slabs

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Message-ID: <edd0197b-7a79-9cb5-8ac5-5d202c2ed51b@linux.com>
Date:   Mon, 30 Oct 2023 20:47:06 -0700 (PDT)
From:   Christoph Lameter <cl@...ux.com>
To:     Chengming Zhou <chengming.zhou@...ux.dev>
cc:     vbabka@...e.cz, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
        roman.gushchin@...ux.dev, 42.hyeyoo@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Chengming Zhou <zhouchengming@...edance.com>
Subject: Re: [RFC PATCH v3 0/7] slub: Delay freezing of CPU partial slabs

On Tue, 31 Oct 2023, Chengming Zhou wrote:

> The current scheme (which this series implemented) is:
>
> - node partial slabs: PG_Workingset (set or clear with per-node list_lock protection)
> - cpu partial slabs: !PG_Workingset

And then the frozen flag needs to be set. Otherwise slab_free() would 
conclude it is on a partial list?

> - cpu slabs: !PG_Workingset && frozen (set or clear using cmpxchg together with freelist)



> - full slabs: !PG_Workingset

And frozen is clear? Otherwise it is the same as a cpu partial slab.

> As Vlastimil noted, it's possible to drop "frozen" bit for cpu slabs, but
> we keep it for performance, since we don't need to grab node list_lock to
> check whether PG_Workingset is set or not if the "frozen" bit is set.
>
> Thanks!
>