linux-kernel - Re: [PATCH 1/2] lockref: speculatively spin waiting for the lock to be released

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Message-ID: <CAHk-=wj0cmLKJZipHy-OcwKADygUgd19yU1rmBaB6X3Wb5jU3Q@mail.gmail.com>
Date: Thu, 13 Jun 2024 10:00:20 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Christian Brauner <brauner@...nel.org>
Cc: Mateusz Guzik <mjguzik@...il.com>, viro@...iv.linux.org.uk, jack@...e.cz, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/2] lockref: speculatively spin waiting for the lock to
 be released

On Thu, 13 Jun 2024 at 06:46, Christian Brauner <brauner@...nel.org> wrote:
>
> I've picked Linus patch and your for testing into the vfs.inode.rcu branch.

Btw, if you added [patch 2/2] too, I think the exact byte counts in
the comments are a bit misleading.

The actual cacheline details will very much depend on 32-bit vs 64-bit
builds, but also on things like the slab allocator debug settings.

I think the important part is to keep the d_lockref - that is often
dirty and exclusive in the cache - away from the mostly RO parts of
the dentry that can be shared across CPU's in the cache.

So rather than talk about exact byte offsets, maybe just state that
overall rule?

              Linus