linux-kernel - Re: [PATCH 1/3] mm/slub: fix the race between validate_slab and slab

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Message-ID: <alpine.DEB.2.22.394.2206021712530.2924@gentwo.de>
Date:   Thu, 2 Jun 2022 17:14:41 +0200 (CEST)
From:   Christoph Lameter <cl@...two.de>
To:     David Rientjes <rientjes@...gle.com>
cc:     Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Rongwei Wang <rongwei.wang@...ux.alibaba.com>,
        akpm@...ux-foundation.org, vbabka@...e.cz,
        roman.gushchin@...ux.dev, iamjoonsoo.kim@....com,
        penberg@...nel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mm/slub: fix the race between validate_slab and
 slab_free

On Mon, 30 May 2022, David Rientjes wrote:

> > Unconditionally taking n->list_lock will degrade performance.
>
> This is a good point, it would be useful to gather some benchmarks for
> workloads that are known to thrash some caches and would hit this path
> such as netperf TCP_RR.

Its obvious that adding new spinlocks to some of the hottest functions in
the kernel will degrade performance. This goes against the basic design of
these functions to be as efficient as possible.