netdev - Re: [PATCH net-next] net: avoid extra acces to sk->sk_wmem_alloc in sock

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Message-ID: <CAAVpQUBCENDVZV1KYujdEnQicaRRa8b_FrusD4N7k=tO4CQJug@mail.gmail.com>
Date: Sun, 19 Oct 2025 12:26:01 -0700
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net-next] net: avoid extra acces to sk->sk_wmem_alloc in sock_wfree()

On Fri, Oct 17, 2025 at 6:37 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> UDP TX packets destructor is sock_wfree().
>
> It suffers from a cache line bouncing in sock_def_write_space_wfree().
>
> Instead of reading sk->sk_wmem_alloc after we just did an atomic RMW
> on it, use __refcount_sub_and_test() to get the old value for free,
> and pass the new value to sock_def_write_space_wfree().
>
> Add __sock_writeable() helper.

Reviewed-by: Kuniyuki Iwashima <kuniyu@...gle.com>

Thanks!