From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-m16.yeah.net (mail-m16.yeah.net [220.197.32.19]) (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 C8DAA46F4BE; Wed, 5 Aug 2026 13:20:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.32.19 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785936052; cv=none; b=sUlCc5m5NJ7VUlbFeCkn0CLneQwJQ1sSBvWP6L/LzR5bBxPap+4iYDFkHpdKBYfymrFs8NxpP4+He+CXLSvLGcrWXMviQcPJFUy3J65GHHfAXuoZPyNmYJJry22+FbEKx0IguGY6GkFQiLTXH9H2jt3BXG489yau7YNTLz1N2rk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785936052; c=relaxed/simple; bh=JMePd5VeyNB0Ef2pt7sFja4wGNwTmMTGZrlBvhZLVP0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=AmGTklQGC2sdOfFJNoVOzblHtY0Z4rZZoQNk/7YRHsj/Ql85bnuf7695+43gxPvTS1WaXLVxHGlTChYPj06SuJ4xYPq14P7xh1hxZ18zADNnYBH67iXFsV5yJUH5t5BQVZkmfgK6Yz/ILiZ8KstfhXaRQpv7jBGbgYZbW9TBShU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=yeah.net; spf=pass smtp.mailfrom=yeah.net; dkim=pass (1024-bit key) header.d=yeah.net header.i=@yeah.net header.b=As+d/VPI; arc=none smtp.client-ip=220.197.32.19 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=yeah.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=yeah.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=yeah.net header.i=@yeah.net header.b="As+d/VPI" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yeah.net; s=s110527; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=xP XoB6ZXcu+Q1U2yXVUy9XxTUSvKqEZ57BrnkUq1mX8=; b=As+d/VPIpS8hmj96mE rWXdx7pTRUsB7prWW32EfDoTTi74gj4tuooA1P/Rn5XloPi9RDnjIc0vaiYRj0u8 pPORAvi3oz29kGO6hvjXbHWeMVZGukT/0+oDtZ3v6RUsME4paqgqQOstzyiO9oNb uK5p0x6xRD49njeFsAwBiy7yk= Received: from deepin (unknown []) by gzsmtp2 (Coremail) with UTF8SMTPSA id Ms8vCgAXEAeBOHNq1DJBAw--.21228S4; Wed, 05 Aug 2026 21:20:21 +0800 (CST) From: Ziran Zhang To: Eric Dumazet , Neal Cardwell , Kuniyuki Iwashima Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Ziran Zhang Subject: [PATCH] tcp: clarify comment for mdev_us in struct tcp_sock Date: Wed, 5 Aug 2026 21:19:27 +0800 Message-ID: <20260805131927.27661-1-zhangcoder@yeah.net> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:Ms8vCgAXEAeBOHNq1DJBAw--.21228S4 X-Coremail-Antispam: 1Uf129KBjvdXoWrtrW5KF45Gry5uw4fuFWUXFb_yoWkuFb_uw 4kZrs2yr1DZFy7Ja18Jr1S9wn3Ww18JF1fWr1rtrsFqw1vkFs3Xw1kJF9a9r4rGFZI9FyD Jwn5ur92qF4fujkaLaAFLSUrUUUUjb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUvcSsGvfC2KfnxnUUI43ZEXa7xR_UUUUUUUUU== X-CM-SenderInfo: x2kd0wpfrgv2o61htxgoqh3/1tbiIRWqa2pzOJVHgAAA3G The existing comment for mdev_us says "medium deviation", but this term is inaccurate. The field stores the "mean deviation" of RTT, as originally defined in Van Jacobson's paper "Congestion Avoidance and Control", and it is scaled by 4 (<< 2) in the Linux implementation. Update the comment to reflect the correct terminology and storage format. Signed-off-by: Ziran Zhang --- include/linux/tcp.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 8a6807082..6a8c77719 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -274,7 +274,7 @@ struct tcp_sock { u32 write_seq; /* Tail(+1) of data held in tcp send buffer */ u32 pushed_seq; /* Last pushed seq, required to talk to windows */ u32 lsndtime; /* timestamp of last sent data packet (for restart window) */ - u32 mdev_us; /* medium deviation */ + u32 mdev_us; /* mean deviation of RTT, scaled by 4 (<< 2) in usecs */ u32 rtt_seq; /* sequence number to update rttvar */ u32 max_packets_out; /* max packets_out in last window */ u32 cwnd_usage_seq; /* right edge of cwnd usage tracking flight */ -- 2.51.0