From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta0.migadu.com (out-188.mta0.migadu.com [91.218.175.188]) (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 8891831578E for ; Fri, 17 Jul 2026 06:03:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784268183; cv=none; b=gVsGwZYJZVzx3K/7LI2qnzeBGNxr4bnKN/qd8nZvL9ObkGDRb+ECZjT3woF8wlghEYA5P2Pi3qa1QiwUFbHVP7+vxRQ2MBf+aKS9qyhOxFFltJMtSkYXhahDw5Xilm7GmM88mO4V499CyYYAwJ49s0Xep4zKdqtX2JuSOMft4j0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784268183; c=relaxed/simple; bh=yRL1J1QpJhkLYIy2lr2EbNTS/wmtg94e30OebBKEFw0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=bJ1UVsMAdzKZ/deiwSVL6B9o/Lg0DO7NNmOARG4BYT2v69DFQ8UZs2rZtYbks2XFDjwvxuRrkKl+e4wnyxW2awV82iJfoKbqt/oNTfs7/+b7CFAqRO88OvLd+2+x+KH3B5+6dkBLGPiHYTTKmG2pb7ov9FL4L1oXlC7VzXfrC6U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=I+eXlpNB; arc=none smtp.client-ip=91.218.175.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="I+eXlpNB" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784268169; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=8IjuMzlv8GEhImlYUewVCFCbHhMBDBXn/IyW5nCXWPM=; b=I+eXlpNBW1eidiQqK0QhU5cgPuY73d8j04T7lV0pBB0xZNwXrnEHBgk2aQp80Bjj3PJcww Ok50OjvWOxdWuxdY+VZJg/A+PcOWM9a2DLYvrZKtKK6T3BF89W2K6mMNblrtLgAV7gzojT XALcK8cW42gEiISiZ57HvLoQp93ZLLI= From: Tao Cui To: Tejun Heo Cc: Johannes Weiner , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Jonathan Corbet , Josef Bacik , Jens Axboe , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, cuitao@kylinos.cn, cui.tao@linux.dev Subject: [PATCH v2 0/2] blk-iolatency: fix io.latency documentation accuracy Date: Fri, 17 Jul 2026 14:02:23 +0800 Message-ID: <20260717060225.2019764-1-cui.tao@linux.dev> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Tao Cui Hi, This series fixes three inaccuracies in the io.latency documentation (Documentation/admin-guide/cgroup-v2.rst), all caused by the doc describing only rotational-device behavior: Patch 1 documents the rotational vs non-rotational difference: throttling is based on average latency on rotational devices but on the fraction of IOs that miss the target on non-rotational devices; the tuning guidance and io.stat field list are updated accordingly (avg_lat/win are rotational-only; missed/total are documented for non-rotational devices). Patch 2 corrects the delay unit: io.stat reports delay_nsec in nanoseconds, not microseconds as the doc stated. Both patches are documentation-only and checkpatch-clean. --- Changes in v2 (address review feedback): - The non-rotational tuning guidance no longer implies missed/total is a latency baseline: iolatency reports no average latency for non-rotational devices, so the target must be chosen from device characteristics and missed/total only verifies it is being met. - missed/total are now described as live counters for the current window (accumulated since the last window boundary), not "the last window": iolatency_ssd_stat() sums the per-cpu counters without resetting them, while they are reset at window end by iolatency_check_latencies(). Tao Cui (2): Docs/admin-guide/cgroup-v2: document io.latency rotational vs non-rotational behavior Docs/admin-guide/cgroup-v2: fix delay_nsec unit in io.latency doc Documentation/admin-guide/cgroup-v2.rst | 55 +++++++++++++++++-------- 1 file changed, 38 insertions(+), 17 deletions(-) -- 2.43.0