From patchwork Wed May 5 01:36:45 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 12238895 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 BB4CDC433B4 for ; Wed, 5 May 2021 01:36:48 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6CEBD61182 for ; Wed, 5 May 2021 01:36:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CEBD61182 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 085688D005C; Tue, 4 May 2021 21:36:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 05BBF8D003B; Tue, 4 May 2021 21:36:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E8EF58D005C; Tue, 4 May 2021 21:36:47 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0126.hostedemail.com [216.40.44.126]) by kanga.kvack.org (Postfix) with ESMTP id CA8A28D003B for ; Tue, 4 May 2021 21:36:47 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 8EDD1180AD5C5 for ; Wed, 5 May 2021 01:36:47 +0000 (UTC) X-FDA: 78105463254.07.E19CBCC Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf26.hostedemail.com (Postfix) with ESMTP id C21BD40002E3 for ; Wed, 5 May 2021 01:36:35 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 0E12B61029; Wed, 5 May 2021 01:36:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620178606; bh=DsraT5Rsc6e2a7LbSNOYjvEvLgiMH2ndQa0pXE9tTaY=; h=Date:From:To:Subject:In-Reply-To:From; b=YjeI3k7UXyjzWTYUnGUvh8/b/3h8Iozw3qhaMiBoR5BX98HDkGMQssTPrj1lfQx06 ZDRAarCADuEdP75wRwF22796iv2dMq8joe9tMgUjQw70KoPXQE0crY5L9/1bVBu2Lm hva8Uz2St4OQnnrZmRVPtpORCmIIHdXeu0sJdIwg= Date: Tue, 04 May 2021 18:36:45 -0700 From: Andrew Morton To: akpm@linux-foundation.org, guro@fb.com, hannes@cmpxchg.org, ktkhai@virtuozzo.com, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, shakeelb@google.com, shy828301@gmail.com, torvalds@linux-foundation.org, vbabka@suse.cz Subject: [patch 074/143] mm: vmscan: shrink deferred objects proportional to priority Message-ID: <20210505013645.nTyzJHMzo%akpm@linux-foundation.org> In-Reply-To: <20210504183219.a3cc46aee4013d77402276c5@linux-foundation.org> User-Agent: s-nail v14.8.16 Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=YjeI3k7U; dmarc=none; spf=pass (imf26.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Stat-Signature: 88ksj6gpz5bbp3yanwdung1pycxrefgg X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C21BD40002E3 Received-SPF: none (linux-foundation.org>: No applicable sender policy available) receiver=imf26; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620178595-110 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: From: Yang Shi Subject: mm: vmscan: shrink deferred objects proportional to priority The number of deferred objects might get windup to an absurd number, and it results in clamp of slab objects. It is undesirable for sustaining workingset. So shrink deferred objects proportional to priority and cap nr_deferred to twice of cache items. The idea is borrowed from Dave Chinner's patch: https://lore.kernel.org/linux-xfs/20191031234618.15403-13-david@fromorbit.com/ Tested with kernel build and vfs metadata heavy workload in our production environment, no regression is spotted so far. Link: https://lkml.kernel.org/r/20210311190845.9708-14-shy828301@gmail.com Signed-off-by: Yang Shi Cc: Johannes Weiner Cc: Kirill Tkhai Cc: Michal Hocko Cc: Roman Gushchin Cc: Shakeel Butt Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/vmscan.c | 46 +++++++++++----------------------------------- 1 file changed, 11 insertions(+), 35 deletions(-) --- a/mm/vmscan.c~mm-vmscan-shrink-deferred-objects-proportional-to-priority +++ a/mm/vmscan.c @@ -664,7 +664,6 @@ static unsigned long do_shrink_slab(stru */ nr = xchg_nr_deferred(shrinker, shrinkctl); - total_scan = nr; if (shrinker->seeks) { delta = freeable >> priority; delta *= 4; @@ -678,37 +677,9 @@ static unsigned long do_shrink_slab(stru delta = freeable / 2; } + total_scan = nr >> priority; total_scan += delta; - if (total_scan < 0) { - pr_err("shrink_slab: %pS negative objects to delete nr=%ld\n", - shrinker->scan_objects, total_scan); - total_scan = freeable; - next_deferred = nr; - } else - next_deferred = total_scan; - - /* - * We need to avoid excessive windup on filesystem shrinkers - * due to large numbers of GFP_NOFS allocations causing the - * shrinkers to return -1 all the time. This results in a large - * nr being built up so when a shrink that can do some work - * comes along it empties the entire cache due to nr >>> - * freeable. This is bad for sustaining a working set in - * memory. - * - * Hence only allow the shrinker to scan the entire cache when - * a large delta change is calculated directly. - */ - if (delta < freeable / 4) - total_scan = min(total_scan, freeable / 2); - - /* - * Avoid risking looping forever due to too large nr value: - * never try to free more than twice the estimate number of - * freeable entries. - */ - if (total_scan > freeable * 2) - total_scan = freeable * 2; + total_scan = min(total_scan, (2 * freeable)); trace_mm_shrink_slab_start(shrinker, shrinkctl, nr, freeable, delta, total_scan, priority); @@ -747,10 +718,15 @@ static unsigned long do_shrink_slab(stru cond_resched(); } - if (next_deferred >= scanned) - next_deferred -= scanned; - else - next_deferred = 0; + /* + * The deferred work is increased by any new work (delta) that wasn't + * done, decreased by old deferred work that was done now. + * + * And it is capped to two times of the freeable items. + */ + next_deferred = max_t(long, (nr + delta - scanned), 0); + next_deferred = min(next_deferred, (2 * freeable)); + /* * move the unused scan count back into the shrinker in a * manner that handles concurrent updates.