linux-kernel - Re: [GIT pull] locking/urgent for v5.15-rc2

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Message-ID: <CAHk-=wgPrw6C-skHMLOR5PNfOtLm1Wyng3Z_eobJBz9BY+Q1ag@mail.gmail.com>
Date:   Mon, 20 Sep 2021 08:23:45 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [GIT pull] locking/urgent for v5.15-rc2

On Mon, Sep 20, 2021 at 4:27 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> Is that XADD really more expensive? I don't think I've ever seen that.

Hmm. Looking at newer tables from Agner Fog, it doesn't seem to be the
big difference it used to be, so maybe not a big deal. It shows up as
many more ups, but the lock synchronization ends up dominating.

I just remember from when xadd weas new, and it was noticeably slower.

                 Linus