From: Thomas Gleixner <tglx@linutronix.de>
To: Christoph Lameter via B4 Relay <devnull+cl.gentwo.org@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Waiman Long <longman@redhat.com>,
Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org,
"Christoph Lameter (Ampere)" <cl@gentwo.org>
Subject: Re: [PATCH v3] Avoid memory barrier in read_seqcount() through load acquire
Date: Tue, 17 Sep 2024 13:52:48 +0200 [thread overview]
Message-ID: <87o74m1oq7.ffs@tglx> (raw)
In-Reply-To: <20240912-seq_optimize-v3-1-8ee25e04dffa@gentwo.org>
On Thu, Sep 12 2024 at 15:44, Christoph Lameter via wrote:
$Subject: .....
You still fail to provide a proper subsystem prefix. It's not rocket science.
https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#patch-subject
> From: "Christoph Lameter (Ampere)" <cl@gentwo.org>
>
> Some architectures support load acquire which can save us a memory
> barrier and save some cycles.
>
> A typical sequence
>
> do {
> seq = read_seqcount_begin(&s);
> <something>
> } while (read_seqcount_retry(&s, seq);
>
> requires 13 cycles on ARM64 for an empty loop. Two read memory
> barriers are needed. One for each of the seqcount_* functions.
>
> We can replace the first read barrier with a load acquire of
> the seqcount which saves us one barrier.
We ....
Please write changelogs using passive voice. 'We' means nothing here.
Thanks,
tglx
next prev parent reply other threads:[~2024-09-17 11:52 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-12 22:44 Christoph Lameter via B4 Relay
2024-09-13 13:41 ` kernel test robot
2024-09-16 17:52 ` Christoph Lameter (Ampere)
2024-09-17 7:37 ` Will Deacon
2024-09-17 11:50 ` Thomas Gleixner
2024-09-18 0:45 ` Vivi, Rodrigo
2024-09-13 13:41 ` kernel test robot
2024-09-17 7:12 ` Will Deacon
2024-09-18 11:03 ` Christoph Lameter (Ampere)
2024-09-18 15:22 ` Linus Torvalds
2024-09-23 16:28 ` Linus Torvalds
2024-10-23 19:45 ` Peter Zijlstra
2024-10-23 20:34 ` Linus Torvalds
2024-10-28 14:10 ` Will Deacon
2024-10-23 23:42 ` Christoph Lameter (Ampere)
2024-10-25 7:42 ` Peter Zijlstra
2024-10-25 19:30 ` Christoph Lameter (Ampere)
2024-09-17 11:52 ` Thomas Gleixner [this message]
2024-09-18 11:11 ` Christoph Lameter (Ampere)
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