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=-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=ham 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 7105EC433ED for ; Wed, 5 May 2021 01:36:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5761561182 for ; Wed, 5 May 2021 01:36:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229985AbhEEBhm (ORCPT ); Tue, 4 May 2021 21:37:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:40694 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231844AbhEEBhl (ORCPT ); Tue, 4 May 2021 21:37:41 -0400 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 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org 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. _