Re: [PATCH v3] Avoid memory barrier in read_seqcount() through load acquire

[Thomas Gleixner]

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@xxxxxxxxxx>
>
> 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