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=-6.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 7BB3FC433ED for ; Tue, 11 May 2021 02:57:56 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EB2D46144F for ; Tue, 11 May 2021 02:57:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB2D46144F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 140E46B006E; Mon, 10 May 2021 22:57:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1181B6B0071; Mon, 10 May 2021 22:57:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F21E26B0072; Mon, 10 May 2021 22:57:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0166.hostedemail.com [216.40.44.166]) by kanga.kvack.org (Postfix) with ESMTP id D650F6B006E for ; Mon, 10 May 2021 22:57:54 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 92758A8D7 for ; Tue, 11 May 2021 02:57:54 +0000 (UTC) X-FDA: 78127440468.27.381E82D Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf01.hostedemail.com (Postfix) with ESMTP id 0D12A500152F for ; Tue, 11 May 2021 02:57:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620701873; 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: in-reply-to:in-reply-to:references:references; bh=HGTw574Zdl38Dm2r00fjJlfZvUmTvOBB3ISzyiZ0v14=; b=HMMTzjeoDDhPvirbICtymRBcu6RX2lcNcHAl94LhrmlEaxNrX5OnDKq07z2LMlXCs/W1Su YAb3XkbL2WU01+l/rOg3UX48Aoeo4fbWuKLPVxrE3Z/12WL+EhazgzuxkksQD3puu6nin8 8WfU7DyjQyXzv3HoYthS9OqyBtekwB0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-28-LEeC4-9OM2CkJTfhjHhQ5Q-1; Mon, 10 May 2021 22:57:51 -0400 X-MC-Unique: LEeC4-9OM2CkJTfhjHhQ5Q-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 92F70800FF0; Tue, 11 May 2021 02:57:50 +0000 (UTC) Received: from T590 (ovpn-12-106.pek2.redhat.com [10.72.12.106]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 335FF5D705; Tue, 11 May 2021 02:57:42 +0000 (UTC) Date: Tue, 11 May 2021 10:57:38 +0800 From: Ming Lei To: Matthew Wilcox Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, Josh Hunt Subject: Re: [LSF/MM/BPF TOPIC] Block device congestion Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=HMMTzjeo; spf=none (imf01.hostedemail.com: domain of ming.lei@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=ming.lei@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 0D12A500152F X-Stat-Signature: yrhymbbh6ekgyezfd6mgjzfj6qq4rffx Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf01; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=170.10.133.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620701870-417238 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: On Mon, May 10, 2021 at 06:48:39PM +0100, Matthew Wilcox wrote: > > I wish to re-nominate this topic from last year: > > https://lore.kernel.org/linux-mm/20191231125908.GD6788@bombadil.infradead.org/ > > I don't think we've made any progress on it, and likely won't until > everybody is forced into a room and the doors are locked. > > >> 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? > > Congestion isn't there anymore. It was always broken as a concept imho, > since it was inherently racy. We used the old batching mechanism in the > legacy stack to signal it, and it only worked for some devices. The old batching and congestion was helpful for some slow devices, since batching can avoid to submit IOs from different tasks concurrently to same queue when queue is busy, so IO order in same task is maintained. I believe Josh is struggling with this issue, and we had one offline talk about this issue. And there was another such old discussion too: https://lore.kernel.org/linux-scsi/20191203022337.GE25002@ming.t460p/ Thanks, Ming