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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 BA563C04EBF for ; Mon, 23 Sep 2019 11:19:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7CCBC20835 for ; Mon, 23 Sep 2019 11:19:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="eJw0klfM" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7CCBC20835 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2E6AB6B0006; Mon, 23 Sep 2019 07:19:11 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 296646B0008; Mon, 23 Sep 2019 07:19:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 15CCD6B000A; Mon, 23 Sep 2019 07:19:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0125.hostedemail.com [216.40.44.125]) by kanga.kvack.org (Postfix) with ESMTP id E38B76B0006 for ; Mon, 23 Sep 2019 07:19:10 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 98CCA181AC9B4 for ; Mon, 23 Sep 2019 11:19:10 +0000 (UTC) X-FDA: 75965938860.07.kite64_5011b2f737b4c X-HE-Tag: kite64_5011b2f737b4c X-Filterd-Recvd-Size: 3734 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf34.hostedemail.com (Postfix) with ESMTP for ; Mon, 23 Sep 2019 11:19:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=dLuDUQ/NDyEM5X4r4w1bfcQ9G8WLEJqV5t9yVHG08lI=; b=eJw0klfM4+vQl5Cr0fR4SPiMB oSMai5fIJYoYQcwD7OyaYpl43j5BsIyKb4pouVSklalGnwt1DM7fa4bN8fZ03aydu4WySTM0JOl+P mrVbEX/SCvhlozvd8e7VzI49v0ZHIT5hEY5zjqQSGfW3I6LepM7n5eSfWtdS2Hr29W+C1cvH5VNWB PDgKg0VxVm1xhGhm0TM4jzwvyZXlnOze3PhQz0ofJXL0vW6+a08GCc42ziINnk35mNyw0epBh98V7 y2/V5vUN9/RA02A5DXN9Jj4NDNU5zIdQB3klxxPxpb0vs9+KTFYDFqdf4jaXjeWytxSwumBLpoPI9 tCL4QvXJw==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.2 #3 (Red Hat Linux)) id 1iCMMu-0002R7-Mn; Mon, 23 Sep 2019 11:19:00 +0000 Date: Mon, 23 Sep 2019 04:19:00 -0700 From: Matthew Wilcox To: Lin Feng Cc: Michal Hocko , corbet@lwn.net, mcgrof@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, keescook@chromium.org, mchehab+samsung@kernel.org, mgorman@techsingularity.net, vbabka@suse.cz, ktkhai@virtuozzo.com, hannes@cmpxchg.org, Jens Axboe , Omar Sandoval , Ming Lei Subject: Is congestion broken? Message-ID: <20190923111900.GH15392@bombadil.infradead.org> References: <20190917115824.16990-1-linf@wangsu.com> <20190917120646.GT29434@bombadil.infradead.org> <20190918123342.GF12770@dhcp22.suse.cz> <6ae57d3e-a3f4-a3db-5654-4ec6001941a9@wangsu.com> <20190919034949.GF9880@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190919034949.GF9880@bombadil.infradead.org> User-Agent: Mutt/1.12.1 (2019-06-15) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Ping Jens? On Wed, Sep 18, 2019 at 08:49:49PM -0700, Matthew Wilcox wrote: > On Thu, Sep 19, 2019 at 10:33:10AM +0800, Lin Feng wrote: > > On 9/18/19 20:33, Michal Hocko wrote: > > > I absolutely agree here. From you changelog it is also not clear what is > > > the underlying problem. Both congestion_wait and wait_iff_congested > > > should wake up early if the congestion is handled. Is this not the case? > > > > For now I don't know why, codes seem should work as you said, maybe I need to > > trace more of the internals. > > But weird thing is that once I set the people-disliked-tunable iowait > > drop down instantly, this is contradictory to the code design. > > Yes, this is quite strange. If setting a smaller timeout makes a > difference, that indicates we're not waking up soon enough. I see > two possibilities; one is that a wakeup is missing somewhere -- ie the > conditions under which we call clear_wb_congested() are wrong. Or we > need to wake up sooner. > > Umm. We have clear_wb_congested() called from exactly one spot -- > clear_bdi_congested(). That is only called from: > > drivers/block/pktcdvd.c > fs/ceph/addr.c > fs/fuse/control.c > fs/fuse/dev.c > fs/nfs/write.c > > Jens, is something supposed to be calling clear_bdi_congested() in the > block layer? blk_clear_congested() used to exist until October 29th > last year. Or is something else supposed to be waking up tasks that > are sleeping on congestion? > >