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Thu, 2 Feb 2023 15:38:58 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by gentwo.de (Postfix) with ESMTP id A5820B0067C; Thu, 2 Feb 2023 15:38:58 +0100 (CET) Date: Thu, 2 Feb 2023 15:38:58 +0100 (CET) From: Christoph Lameter To: Marcelo Tosatti cc: Aaron Tomlin , Frederic Weisbecker , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 3/5] mm/vmstat: use cmpxchg loop in cpu_vm_stats_fold In-Reply-To: <20230201195104.460373427@redhat.com> Message-ID: References: <20230201195013.881721887@redhat.com> <20230201195104.460373427@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 8AF374000E X-Stat-Signature: fmzcdawgna8szz8uxnqi7bz88dd3qbyo X-Rspam-User: X-HE-Tag: 1675348740-303203 X-HE-Meta: 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 LWm4gLkL YVFxw6HP9LazMQxywbgJ9R4bPX+QvJ+5f2L3P0q0/ma78vpL+YXH4Rhf1QkdP92bNAVvftXuJrg/ozn/0t5eJvne39vGEPEQdxJKVbaEH6/uwPLtkXgy7A5+6692X0ZA5rug9aU/fmqjU2wbGoQjMYTzvozbFggYklzu6cn6IaZMvYKI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 1 Feb 2023, Marcelo Tosatti wrote: > In preparation to switch vmstat shepherd to flush > per-CPU counters remotely, use a cmpxchg loop > instead of a pair of read/write instructions. You are mixing full atomic cmpxchg and per cpu atomic cmpxchg? That does not work. I thought you would only run this while the kernel is not active on the remote cpu? Then you dont need any cmpxchg and you can leave the function as is.