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 X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C63B0C43613 for ; Thu, 20 Jun 2019 16:42:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9E7A22084E for ; Thu, 20 Jun 2019 16:42:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561048958; bh=zCmrEJj/5YbT7k1NdU6eqr1+CknKTQwhJf0kK5Gd8tQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=pRsAOsO449/6Xv6SVel0D/SJPSAo1+39NJNNMCWRykTFgn9nQrEK6m+XyJfIhV4Tr +J5M4GVFPe/Oxguz1ld7C5fQdkIDupPyVOojX7K+TMfBrPcduzWruFknW7ZbkxTzex rVHMNckdXXCD1Pe2WCecl2CjBN6iJz7KlTbJZ0Gk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726832AbfFTQmd (ORCPT ); Thu, 20 Jun 2019 12:42:33 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:42634 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726686AbfFTQmd (ORCPT ); Thu, 20 Jun 2019 12:42:33 -0400 Received: by mail-pf1-f193.google.com with SMTP id q10so1974446pff.9; Thu, 20 Jun 2019 09:42:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=bqZIqiC2yYn/o+bV0ZJOLIzThjXkYn2uG9o9ZjJa6hk=; b=aJXjIKNZrOuVv0daHxeRKl26YhxSc7OxATe5g5agihcDutsVoV8QnJ+dWHiIwzAqCl pE3HVL5RjrWIZ65jZwG7ltBKSmTmkK6K2/Xo2kFkAyDDgTnggrNWOIISIuq+gbgn3ZhE TzCcMB28dJ8/yPURo0HTYeZGCtDEvpXaHVy/wsVQIX4D1+y7DXNiq7rWv7UezTTztVFF ox2doav/9GzUNq10RwePuy778KcpEt1dS9tx0TntQAeO5b4OhUkUJNte1QYUqFi7iZpT Q90SNo8xa+f69+YZunlcowN/DQxZLoqaTE8KgQiJiwxAFO8hbAGbKmTLK0E+Ldg2mW2j xb5w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=bqZIqiC2yYn/o+bV0ZJOLIzThjXkYn2uG9o9ZjJa6hk=; b=Gn3ufQbMmS9lyKecpgnpUgae0K1WJ60+qta2hBq/bzxR64Q2JKjF0k7cgS9KZ0jKcd whaSHj/ZzvsNfShat1WTEOcI+1BeiPfm7NqqcTA/ZxX3NJb4VZuSRaKlsy4z+mqgHzp5 jvHX38mpUEFSMdUd6YGHPfUupSDzPv/BZlVLxqE8+Bx4OT7mRUyjiSkY7FEuFJr8Tt4S u4+ZIK+G6l3DVejoc2j/P94EI99eFbGLt3DdVLcxJzXdrAbyRGIm3IsRej0XHwPLmKD/ ksC4YI2pj7CW/0EEDThegT9SZhlKf6WZ5eCKW3egxqY18pvrwI21zanIXLEWzT4upw9Y cJrg== X-Gm-Message-State: APjAAAU8tqwbUnho48umq1IQGJVPhzoxRcF69EU+nqEdeBhAYCDmR9an kVDuuNd5L1HVWpcwhxL6Flw= X-Google-Smtp-Source: APXvYqx072QE6ne/M+YjuzM0WPDx/elSTOitdaIoOS9wonauvSK6+p09K5VLrDBRVcopCvc7fjOCow== X-Received: by 2002:a17:90a:bc0c:: with SMTP id w12mr496330pjr.111.1561048952289; Thu, 20 Jun 2019 09:42:32 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::3:8402]) by smtp.gmail.com with ESMTPSA id y16sm2426pff.89.2019.06.20.09.42.31 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Jun 2019 09:42:31 -0700 (PDT) Date: Thu, 20 Jun 2019 09:42:29 -0700 From: Tejun Heo To: Jan Kara Cc: dsterba@suse.com, clm@fb.com, josef@toxicpanda.com, axboe@kernel.dk, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 4/9] blkcg: implement REQ_CGROUP_PUNT Message-ID: <20190620164229.GK657710@devbig004.ftw2.facebook.com> References: <20190615182453.843275-1-tj@kernel.org> <20190615182453.843275-5-tj@kernel.org> <20190620153733.GM30243@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190620153733.GM30243@quack2.suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hello, Jan. On Thu, Jun 20, 2019 at 05:37:33PM +0200, Jan Kara wrote: > > +bool __blkcg_punt_bio_submit(struct bio *bio) > > +{ > > + struct blkcg_gq *blkg = bio->bi_blkg; > > + > > + /* consume the flag first */ > > + bio->bi_opf &= ~REQ_CGROUP_PUNT; > > + > > + /* never bounce for the root cgroup */ > > + if (!blkg->parent) > > + return false; > > + > > + spin_lock_bh(&blkg->async_bio_lock); > > + bio_list_add(&blkg->async_bios, bio); > > + spin_unlock_bh(&blkg->async_bio_lock); > > + > > + queue_work(blkcg_punt_bio_wq, &blkg->async_bio_work); > > + return true; > > +} > > + > > So does this mean that if there is some inode with lots of dirty data for a > blkcg that is heavily throttled, that blkcg can occupy a ton of workers all > being throttled in submit_bio()? Or what is constraining a number of > workers one blkcg can consume? There's only one work item per blkcg-device pair, so the maximum number of kthreads a blkcg can occupy on a filesystem would be one. It's the same scheme as writeback work items. Thanks. -- tejun