From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-171.mta1.migadu.com (mta1.migadu.com [37.59.57.117]) (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 B540D3CF21C for ; Mon, 10 Aug 2026 12:09:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=37.59.57.117 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786363744; cv=none; b=JwTMY2zy8bX24+SFGICN+NRQVd9VQRHsgexyIrvHBdO/X4DdHePM7FXV0Lto3FcugB++vBw+3oy8H9vZ/k8MrvzLE3qYGDCX3TRFN8h13ugHjPwKJh4H7lddVdMPqJwWovk/NGp4WTGB4CaZz7bvpKgEIAEfKig85SYOar1hV30= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786363744; c=relaxed/simple; bh=XV8ZxqjRpLLLQfuYlGbp2be1V8T05rOZBfoW/R//gq0=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=r+id95Z2B7NUeYfsOEQ8msvHBw4L2pQhiQ9A1/KqmkTJkgsLLIZNvHI8ZwDZV3nAWmbw294B+Ay+e9Cv0qOfyDut0jZwN21n1zPNrkMbf8I/aB6yYmkr3Tb1L2/8xNajINpz4toe0b6JBe/mKa7WTCwwPAdjcwj1XTgrropiDIU= 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=A9FgdG6g; arc=none smtp.client-ip=37.59.57.117 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="A9FgdG6g" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1786363740; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=XfsMqSeEbgZlvWkzIrsOLohICZgYToyeJ6wB2SRONMU=; b=A9FgdG6gYSb3GwmO8fErIpXg6ahWYKzJ2jADd0yPWE6v3Cnez/DMb0dEMuZVSAhz6mjLoQ Gen5djuSYapncDwY7QHOtTqmPlT62rjvGzh7SbM2R507WHFKOHqvoCTB+m7ObxL8K0AJSi HUeECVZJtVRTio9SInQ5WV/7lgxwMF4= Date: Mon, 10 Aug 2026 20:08:08 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Cc: cui.tao@linux.dev, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] docs: cgroup-v2: fix stale "io" controller introduction To: Zhe Liu , tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, corbet@lwn.net, skhan@linuxfoundation.org References: <20260810063535.327765-1-liuzhe1@kylinos.cn> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Tao Cui In-Reply-To: <20260810063535.327765-1-liuzhe1@kylinos.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 在 2026/8/10 14:35, Zhe Liu 写道: > The introductory paragraph for the IO controller still states that > weight based distribution is "available only if cfq-iosched is in use" > and that "neither scheme is available for blk-mq devices". This text > dates from when the cgroup v2 documentation was first written (2015) > and was correct at the time, but is no longer accurate: > > * cfq-iosched was removed in v4.12; > * blk-mq is now the only block I/O path, and both the absolute limit > scheme (io.max via blk-throttle) and the weight based scheme > (io.weight via iocost, or io.bfq.weight under BFQ) work on it; > * latency based protection (iolatency) and I/O priority (ioprio) > controllers have since been added. > cfq-iosched was removed in v5.0, not v4.12 (f382fb0bcef4, "block: remove legacy IO schedulers"). v4.12 only added the blk-mq schedulers; cfq-iosched.c stayed until v5.0. Otherwise looks good. Reviewed-by: Tao Cui > The rest of the section already documents io.weight, io.max, > io.cost.{qos,model}, io.latency and io.prio.class correctly, so the > introduction is the only part that contradicts them. Rewrite it to > reflect the current state. > > Signed-off-by: Zhe Liu > --- > Documentation/admin-guide/cgroup-v2.rst | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst > index aed195a71cbf..0fbc7c963807 100644 > --- a/Documentation/admin-guide/cgroup-v2.rst > +++ b/Documentation/admin-guide/cgroup-v2.rst > @@ -1984,9 +1984,13 @@ IO > > The "io" controller regulates the distribution of IO resources. This > controller implements both weight based and absolute bandwidth or IOPS > -limit distribution; however, weight based distribution is available > -only if cfq-iosched is in use and neither scheme is available for > -blk-mq devices. > +limit distribution. Absolute BPS and IOPS limits are enforced by > +blk-throttle and apply to all devices, while weight based proportional > +distribution is provided by the iocost cost model controller > +(CONFIG_BLK_CGROUP_IOCOST) and, when the BFQ I/O scheduler is in use > +for a device, by BFQ's own cgroup support. Latency-based protection > +(CONFIG_BLK_CGROUP_IOLATENCY) and I/O priority assignment > +(CONFIG_BLK_CGROUP_IOPRIO) are also available. > > > IO Interface Files