From: Jakub Kicinski <kuba@kernel.org>
To: Eric Dumazet <edumazet@google.com>
Cc: "David S . Miller" <davem@davemloft.net>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
Neal Cardwell <ncardwell@google.com>,
Kuniyuki Iwashima <kuniyu@google.com>,
Willem de Bruijn <willemb@google.com>,
netdev@vger.kernel.org, eric.dumazet@gmail.com
Subject: Re: [PATCH v2 net-next 0/9] tcp: avoid struct socket cache line miss in tcp_check_space()
Date: Mon, 28 Sep 2026 18:18:54 -0700 [thread overview]
Message-ID: <20260928181854.0b520fcf@kernel.org> (raw)
In-Reply-To: <20260924134729.2047213-1-edumazet@google.com>
On Thu, 24 Sep 2026 13:47:20 +0000 Eric Dumazet wrote:
> tcp_check_space() is called on every incoming ACK and every transmitted
> packet, and tests SOCK_NOSPACE in sk->sk_socket->flags. Because struct
> socket lives in its own cache line and the TCP fast paths do not touch
> it for anything else, that test pulls in an extra cache line that is
> cold when the working set of active sockets is large.
>
> This series mirrors SOCK_NOSPACE into a new u8 field, tp->tcp_nospace,
> placed right after tp->chrono_type in the tcp_sock_write_tx cache line
> group (fitting in an existing 3-byte hole before chrono_start, so no
> other field moves and sizeof(struct tcp_sock) is unchanged). Both the
> transmit and ACK fast paths already touch that cache line, making the
> fast-path test in tcp_check_space() free of extra cache misses while
> keeping __tcp_check_space() authoritative on SOCK_NOSPACE.
Please resend this and CC the maintainers of the code we're about
to change.
--
pw-bot: cr
prev parent reply other threads:[~2026-09-29 1:18 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-24 13:47 [PATCH v2 net-next 0/9] tcp: avoid struct socket cache line miss in tcp_check_space() Eric Dumazet
2026-09-24 13:47 ` [PATCH v2 net-next 1/9] dlm: fix send buffer backpressure handling Eric Dumazet
2026-09-25 13:49 ` netdev-bot+sashiko
2026-09-24 13:47 ` [PATCH v2 net-next 2/9] net: add sk_set_nospace() and sk_clear_nospace() Eric Dumazet
2026-09-25 13:49 ` netdev-bot+sashiko
2026-09-24 13:47 ` [PATCH v2 net-next 3/9] sunrpc: use " Eric Dumazet
2026-09-24 13:47 ` [PATCH v2 net-next 4/9] rds: use sk_set_nospace() Eric Dumazet
2026-09-24 13:47 ` [PATCH v2 net-next 5/9] dlm: use sk_set_nospace() and sk_clear_nospace() Eric Dumazet
2026-09-24 13:47 ` [PATCH v2 net-next 6/9] drbd: use sk_set_nospace() Eric Dumazet
2026-09-24 13:47 ` [PATCH v2 net-next 7/9] nvme-tcp: use sk_clear_nospace() Eric Dumazet
2026-09-24 13:47 ` [PATCH v2 net-next 8/9] libceph: " Eric Dumazet
2026-09-24 13:47 ` [PATCH v2 net-next 9/9] tcp: add tp->tcp_nospace Eric Dumazet
2026-09-29 1:18 ` Jakub Kicinski [this message]
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