From patchwork Mon Sep 20 08:54:31 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mel Gorman X-Patchwork-Id: 12504923 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=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT 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 308BFC433F5 for ; Mon, 20 Sep 2021 09:14:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 117B860F26 for ; Mon, 20 Sep 2021 09:14:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229968AbhITJPe (ORCPT ); Mon, 20 Sep 2021 05:15:34 -0400 Received: from outbound-smtp14.blacknight.com ([46.22.139.231]:46319 "EHLO outbound-smtp14.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236759AbhITJPQ (ORCPT ); Mon, 20 Sep 2021 05:15:16 -0400 Received: from mail.blacknight.com (pemlinmail02.blacknight.ie [81.17.254.11]) by outbound-smtp14.blacknight.com (Postfix) with ESMTPS id A52EA1C535E for ; Mon, 20 Sep 2021 09:54:47 +0100 (IST) Received: (qmail 26556 invoked from network); 20 Sep 2021 08:54:47 -0000 Received: from unknown (HELO stampy.112glenside.lan) (mgorman@techsingularity.net@[84.203.17.29]) by 81.17.254.9 with ESMTPA; 20 Sep 2021 08:54:47 -0000 From: Mel Gorman To: Linux-MM Cc: NeilBrown , Theodore Ts'o , Andreas Dilger , "Darrick J . Wong" , Matthew Wilcox , Michal Hocko , Dave Chinner , Rik van Riel , Vlastimil Babka , Johannes Weiner , Jonathan Corbet , Linux-fsdevel , LKML , Mel Gorman Subject: [RFC PATCH 0/5] Remove dependency on congestion_wait in mm/ Date: Mon, 20 Sep 2021 09:54:31 +0100 Message-Id: <20210920085436.20939-1-mgorman@techsingularity.net> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Cc list similar to "congestion_wait() and GFP_NOFAIL" as they're loosely related. This is a prototype series that removes all calls to congestion_wait in mm/ and deletes wait_iff_congested. It's not a clever implementation but congestion_wait has been broken for a long time (https://lore.kernel.org/linux-mm/45d8b7a6-8548-65f5-cccf-9f451d4ae3d4@kernel.dk/). Even if it worked, it was never a great idea. While excessive dirty/writeback pages at the tail of the LRU is one possibility that reclaim may be slow, there is also the problem of too many pages being isolated and reclaim failing for other reasons (elevated references, too many pages isolated, excessive LRU contention etc). This series replaces the reclaim conditions with event driven ones o If there are too many dirty/writeback pages, sleep until a timeout or enough pages get cleaned o If too many pages are isolated, sleep until enough isolated pages are either reclaimed or put back on the LRU o If no progress is being made, let direct reclaim tasks sleep until another task makes progress This has been lightly tested only and the testing was useless as the relevant code was not executed. The workload configurations I had that used to trigger these corner cases no longer work (yey?) and I'll need to implement a new synthetic workload. If someone is aware of a realistic workload that forces reclaim activity to the point where reclaim stalls then kindly share the details.