From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 37EF3C98302 for ; Tue, 22 Sep 2026 15:53:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=cOoptst2ZoEH8nVl0gkhYSEwxHVp5gsU3BDINyMPqCg=; b=OjUsLDbEmubwm97v5KKoCM2unC W8HHjN0nh7dAKUsyv9wVYYyY21/EpvK6Otmj8WRuJsQEuuwE4SumgEEZdxRYqGsRNJXVX72fgsMD0 6weiHIV6U6A3uHKVousavlKOYWDVwa11Zv3ZYvNwTd+UiTNpMWZ4Xz0+urvCEeHEDG8/fTf2nUONj fdeduuzrq7ULygBDlPFrkK/b4+KrDVnfPBGNAUbIrw1szsOMHyryp9NUbrP6gg+kGoLhEJE6s8Zqt x1/yrOdJuTh0HiJU4DJ15HU+U7xNUNRM3j+rDFTyivgr6lSq5DuHit7w4TuHootTw4dirdk6NB2ps dGho4ZEg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x92oB-00000005x8R-0OAQ; Tue, 22 Sep 2026 15:53:27 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x92oA-00000005x7k-1XOj for linux-nvme@lists.infradead.org; Tue, 22 Sep 2026 15:53:26 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id BEACB40BFA; Tue, 22 Sep 2026 15:53:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7903B1F000FF; Tue, 22 Sep 2026 15:53:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790092405; bh=cOoptst2ZoEH8nVl0gkhYSEwxHVp5gsU3BDINyMPqCg=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=L3RxkiWKuROFiw8J6LgOeWwybKXn/pxST7eaRsKu9zbMuQCmcYr65EAki0pMmLGsY QUnb1BPV09sM7D1bFA2bKnGLSB7AwqLsxKbt9PIO7p9uzvx/q+SK+SeHtm644Yiuxg 17lcVpXlyKlVCcMpVaqNBkaTnOkeDJzXqYDnw2/YhohjTtAzpZSHD13XMfpZqfCRBL wWoxESvTFgzXA6rqIQ4ltkXf+AN7zzarNPQYkokHpPwaDb9gdVV1HigU7KlMvwRm+b Dt+OkORRzZ3i/hIcAfUad0sq3sBkC72jD6fvb3nVn3XNeYPurIstKX/lZ8Nsev9lVu tq+HaVv6ccheQ== Date: Tue, 22 Sep 2026 05:53:24 -1000 From: Tejun Heo To: Tao Cui Cc: axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, yukuai@fygo.io, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, cuitao@kylinos.cn Subject: Re: [RFC PATCH 1/1] block: charge passthrough requests to the submitter's cgroup Message-ID: References: <20260921070647.1928289-1-cui.tao@linux.dev> <20260921070647.1928289-2-cui.tao@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org Hello, On Tue, Sep 22, 2026 at 04:09:57PM +0800, Tao Cui wrote: > I don't have a specific passthrough workload that triggered this in > production. I ran into it while testing blk-iocost accounting coverage. > > The relevant concern here is cgroup IO isolation. The expectation of > blkcg IO control is that the IO consumed by a cgroup is reflected in its > accounting and subject to blkcg IO policies. Today that is true for IO > going through submit_bio(), but not for passthrough requests. > > The concrete observation was that the same cgroup issuing equivalent > writes through two paths gets different results: normal bio IO is > accounted in io.stat and subject to blkcg IO policies, while SG_IO > writes consume device bandwidth without accounting or blkcg IO control. > > So the motivation is not a particular SG_IO application, but whether > passthrough IO should be considered part of the IO usage controlled by > blkcg. > > I don't know yet whether the right answer is always-on behavior or an > opt-in mechanism. The RFC was mainly to discuss whether passthrough > paths should be covered by blkcg accounting/enforcement at all. SG_IO requires CAP_RAW_IO, so any kind of isolation isn't gonna work out that well. This is an imaginary use case. Please stop until it become an actual one. Thanks. -- tejun