From: Matthew Wilcox <willy@infradead.org>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Christoph Lameter <cl@linux.com>,
Aaron Tomlin <atomlin@atomlin.com>,
Frederic Weisbecker <frederic@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 3/5] mm/vmstat: use cmpxchg loop in cpu_vm_stats_fold
Date: Mon, 6 Feb 2023 19:19:06 +0000 [thread overview]
Message-ID: <Y+FSqkDYfhKuBZIe@casper.infradead.org> (raw)
In-Reply-To: <20230201195104.460373427@redhat.com>
On Wed, Feb 01, 2023 at 04:50:16PM -0300, 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.
FYI, try_cmpxchg() is preferred to plain cmpxchg() these days.
Apparently it generates better code on x86.
> - v = pzstats->vm_stat_diff[i];
> - pzstats->vm_stat_diff[i] = 0;
> + do {
> + v = pzstats->vm_stat_diff[i];
> + } while (cmpxchg(&pzstats->vm_stat_diff[i], v, 0) != v);
I think this would be:
do {
v = pzstats->vm_stat_diff[i];
} while (!try_cmpxchg(&pzstats->vm_stat_diff[i], v, 0));
next prev parent reply other threads:[~2023-02-06 19:19 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-01 19:50 [PATCH 0/5] fold per-CPU vmstats remotely Marcelo Tosatti
2023-02-01 19:50 ` [PATCH 1/5] mm/vmstat: remove remote node draining Marcelo Tosatti
2023-02-01 19:50 ` [PATCH 2/5] mm/vmstat: switch counter modification to cmpxchg Marcelo Tosatti
2023-02-01 19:50 ` [PATCH 3/5] mm/vmstat: use cmpxchg loop in cpu_vm_stats_fold Marcelo Tosatti
2023-02-02 14:38 ` Christoph Lameter
2023-02-02 15:54 ` Marcelo Tosatti
2023-02-03 9:34 ` Christoph Lameter
2023-02-03 18:52 ` Marcelo Tosatti
2023-02-06 9:42 ` Christoph Lameter
2023-02-06 19:10 ` Marcelo Tosatti
2023-02-06 19:19 ` Matthew Wilcox [this message]
2023-02-01 19:50 ` [PATCH 4/5] mm/vmstat: switch vmstat shepherd to flush per-CPU counters remotely Marcelo Tosatti
2023-02-01 19:50 ` [PATCH 5/5] mm/vmstat: refresh stats remotely instead of via work item Marcelo Tosatti
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