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=-15.7 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 6247CC433E9 for ; Wed, 24 Feb 2021 20:05:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 20F2564E6C for ; Wed, 24 Feb 2021 20:05:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235223AbhBXUFh (ORCPT ); Wed, 24 Feb 2021 15:05:37 -0500 Received: from mail.kernel.org ([198.145.29.99]:56868 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235480AbhBXUDy (ORCPT ); Wed, 24 Feb 2021 15:03:54 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id DF54964F0D; Wed, 24 Feb 2021 20:03:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1614196989; bh=gRejEKoFluiBxWJ6U1UkCg86trl6uLiF3N4Bv/ikOiY=; h=Date:From:To:Subject:In-Reply-To:From; b=0c+NRm+GaXwfSjlN2hmXJJrElBvtZWLoF9Bm8Ee461wybC6QV+vaKIgFtABNLJGrZ zC67pA5D0zXH76j+QJ4z7+f23H7sj5Pjl0g8Aeda/oRFAHqSy7Jb1QPAROvvXHG/HH fE3nWPhNHlzqspJalSAnFXLHTdYGtyg0na31bsJI= Date: Wed, 24 Feb 2021 12:03:08 -0800 From: Andrew Morton To: akpm@linux-foundation.org, hannes@cmpxchg.org, iamjoonsoo.kim@lge.com, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, vbabka@suse.cz, yuzhao@google.com Subject: [patch 054/173] mm/swap: don't SetPageWorkingset unconditionally during swapin Message-ID: <20210224200308.c29_ITugV%akpm@linux-foundation.org> In-Reply-To: <20210224115824.1e289a6895087f10c41dd8d6@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: Yu Zhao Subject: mm/swap: don't SetPageWorkingset unconditionally during swapin We are capable of SetPageWorkingset based on refault distances after commit aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU"). This is done by workingset_refault(), which is right above the unconditional SetPageWorkingset deleted by this patch. The unconditional SetPageWorkingset miscategorizes pages that are read ahead or never belonged to the working set (e.g., tmpfs pages accessed only once by fd). When those pages are swapped in (after they were swapped out) for the first time, they skew PSI (when using async swap). When this happens again, depending on their refault distances, they might skew workingset_restore_anon counter in addition to PSI because their shadows indicate they were part of the working set. Historically, SetPageWorkingset was added as part of the PSI series, and Johannes said: "It was meant to mark incoming pages under IO with SetPageWorkingset when waiting for them constituted a memory stall. On the page cache side, because we HAVE workingset detection, this was specific to recently evicted pages that had been active in their previous life. On the anon side, the aging algorithm had no distinction between workingset and sporadically used pages. Given the choice between a) no swapin stalls are pressure and b) all swapin stalls are pressure, I went with the latter in order to detect swap storms. The false positive case - high rate of swapin without severe memory pressure - was relatively unlikely, because we tried to avoid swapping until everything was completely on fire in the first place." Link: https://lkml.kernel.org/r/20201209012400.1771150-1-yuzhao@google.com Link: https://lkml.kernel.org/r/20201214231253.62313-1-yuzhao@google.com Signed-off-by: Yu Zhao Acked-by: Vlastimil Babka Acked-by: Johannes Weiner Acked-by: Joonsoo Kim Acked-by: Michal Hocko Signed-off-by: Andrew Morton --- mm/swap_state.c | 1 - 1 file changed, 1 deletion(-) --- a/mm/swap_state.c~mm-swap-dont-setpageworkingset-unconditionally-during-swapin +++ a/mm/swap_state.c @@ -537,7 +537,6 @@ struct page *__read_swap_cache_async(swp workingset_refault(page, shadow); /* Caller will initiate read into locked page */ - SetPageWorkingset(page); lru_cache_add(page); *new_page_allocated = true; return page; _