From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 96D8B1DFD8B for ; Mon, 20 Oct 2025 15:44:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760975055; cv=none; b=l7SWGGG+teBE98QWhmfkPSqC2csY+rn5YfITnLJDQvB0ARjzL0XFCXXLLPLMXeqF873sLmX62pN5FcYvs1Fh8j8/0+/eWA4+ekqN+y4ja9jopFt2WGCvlzNTuxs6ii5L86Il5UmC1gOv88BnBwElqpGyS8R0tsPzVZDJQ4o5M4w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760975055; c=relaxed/simple; bh=xtWxsZh22PlcE/WlJx1Vqupr3RA2g+V7cFGMgPFocUs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sjis9QJ4ga224yy2ldBTz0jdiOr0xgQjWwjEFYvti6BgXU6RwcaKJkaWjLmX0ALAJ7NbS4fzzuGpYl7ZxMxTkBhXS2W5wclYPf9tj/Th0WiONgEuTfM5GpPfvz1q/UUrs62xaaZW9DvCcWYE6Q9ISbFEEACNqx1TpjKaYP6g2U8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MVBHJlxF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MVBHJlxF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D12DC113D0; Mon, 20 Oct 2025 15:44:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760975055; bh=xtWxsZh22PlcE/WlJx1Vqupr3RA2g+V7cFGMgPFocUs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MVBHJlxFDo9xQv+jlZjXS07fagcOUOKbcLayj+T/ARA16iAJLJacUFt3jMZOMtxaD dJBXnj6AaAtsE935m0euSakFH/zn4a5cyUZSrjKcxn1Ln3Hl9QKeaOcTLjwJyxkXce 4ESyFzdpP+sZnsxAb2P+w9BvTFHLoSp3zpqFlckWwAz1b/QruwTcBD7W47co+6pM9E 5ZXGf8wUFHug7yqWpI++4hUoHDSebGtK63ztSJLiN5BPL4AMz71M+GEyQX5Iyq0YBK +bcl1sHRLoAAEv3B9yijyXcc/fU99jqw4hmqVPDgeVI6iasJFOxvx4vrbK6pxn/VA9 e+1ZShCW5jOSQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Eric Dumazet , Jason Xing , Neal Cardwell , Kuniyuki Iwashima , Paolo Abeni , Sasha Levin Subject: [PATCH 6.12.y 2/8] tcp: cache RTAX_QUICKACK metric in a hot cache line Date: Mon, 20 Oct 2025 11:44:03 -0400 Message-ID: <20251020154409.1823664-2-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251020154409.1823664-1-sashal@kernel.org> References: <2025101604-chamber-playhouse-5278@gregkh> <20251020154409.1823664-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Eric Dumazet [ Upstream commit 15492700ac41459b54a6683490adcee350ab11e3 ] tcp_in_quickack_mode() is called from input path for small packets. It calls __sk_dst_get() which reads sk->sk_dst_cache which has been put in sock_read_tx group (for good reasons). Then dst_metric(dst, RTAX_QUICKACK) also needs extra cache line misses. Cache RTAX_QUICKACK in icsk->icsk_ack.dst_quick_ack to no longer pull these cache lines for the cases a delayed ACK is scheduled. After this patch TCP receive path does not longer access sock_read_tx group. Signed-off-by: Eric Dumazet Reviewed-by: Jason Xing Reviewed-by: Neal Cardwell Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250312083907.1931644-1-edumazet@google.com Signed-off-by: Paolo Abeni Stable-dep-of: 833d4313bc1e ("mptcp: reset blackhole on success with non-loopback ifaces") Signed-off-by: Sasha Levin --- include/net/inet_connection_sock.h | 3 ++- net/core/sock.c | 6 +++++- net/ipv4/tcp_input.c | 3 +-- 3 files changed, 8 insertions(+), 4 deletions(-) diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h index 4bd93571e6c1b..bcc138ff087bd 100644 --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -116,7 +116,8 @@ struct inet_connection_sock { #define ATO_BITS 8 __u32 ato:ATO_BITS, /* Predicted tick of soft clock */ lrcv_flowlabel:20, /* last received ipv6 flowlabel */ - unused:4; + dst_quick_ack:1, /* cache dst RTAX_QUICKACK */ + unused:3; unsigned long timeout; /* Currently scheduled timeout */ __u32 lrcvtime; /* timestamp of last received data packet */ __u16 last_seg_size; /* Size of last incoming segment */ diff --git a/net/core/sock.c b/net/core/sock.c index d392cb37a864f..b5723adab4ebf 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2547,8 +2547,12 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst) u32 max_segs = 1; sk->sk_route_caps = dst->dev->features; - if (sk_is_tcp(sk)) + if (sk_is_tcp(sk)) { + struct inet_connection_sock *icsk = inet_csk(sk); + sk->sk_route_caps |= NETIF_F_GSO; + icsk->icsk_ack.dst_quick_ack = dst_metric(dst, RTAX_QUICKACK); + } if (sk->sk_route_caps & NETIF_F_GSO) sk->sk_route_caps |= NETIF_F_GSO_SOFTWARE; if (unlikely(sk->sk_gso_disabled)) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 4c8d84fc27ca3..1d9e93a04930b 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -331,9 +331,8 @@ static void tcp_enter_quickack_mode(struct sock *sk, unsigned int max_quickacks) static bool tcp_in_quickack_mode(struct sock *sk) { const struct inet_connection_sock *icsk = inet_csk(sk); - const struct dst_entry *dst = __sk_dst_get(sk); - return (dst && dst_metric(dst, RTAX_QUICKACK)) || + return icsk->icsk_ack.dst_quick_ack || (icsk->icsk_ack.quick && !inet_csk_in_pingpong_mode(sk)); } -- 2.51.0