linux-kernel - Re: [PATCH v8 00/13] fold per-CPU vmstats remotely

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Message-ID: <b1f75dca-5d86-125f-bbba-7b575b62d21@gentwo.de>
Date:   Tue, 16 May 2023 10:09:02 +0200 (CEST)
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,
        Russell King <linux@...linux.org.uk>,
        Huacai Chen <chenhuacai@...nel.org>,
        Heiko Carstens <hca@...ux.ibm.com>, x86@...nel.org,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v8 00/13] fold per-CPU vmstats remotely

The patchset still modifies the semantics of this_cpu operations semantics
replacing the lockless RMV operations with locked ones. One of the
rationales for the use  this_cpu operations is their efficiency since
locked RMV atomics are avoided. This patchset destroys that functionality.

If you want locked RMV semantics then use them through cmpxchg() and
friends. Do not modify this_cpu operations by changing the implementation
in the arch code.