linux-kernel - Re: [PATCH v2 02/11] this_cpu_cmpxchg: ARM64: switch this_cpu_cmpxchg to locked, add

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Date:   Thu, 16 Mar 2023 00:56:20 +0100 (CET)
From:   Christoph Lameter <cl@...two.de>
To:     Marcelo Tosatti <mtosatti@...hat.com>
cc:     Aaron Tomlin <atomlin@...mlin.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 02/11] this_cpu_cmpxchg: ARM64: switch this_cpu_cmpxchg
 to locked, add _local function

On Thu, 9 Feb 2023, Marcelo Tosatti wrote:

> Goal is to have vmstat_shepherd to transfer from
> per-CPU counters to global counters remotely. For this,
> an atomic this_cpu_cmpxchg is necessary.

The definition for this_cpu_functionality is that it is *not* incurring
atomic overhead and it was introduced to *avoid* the overhead of atomic
operations.

This sabotages this_cpu functionality,