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=-5.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 A586EC2D0E3 for ; Tue, 8 Sep 2020 20:13:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A6B52145D for ; Tue, 8 Sep 2020 20:13:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chrisdown.name header.i=@chrisdown.name header.b="d04XD4wu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730092AbgIHUNX (ORCPT ); Tue, 8 Sep 2020 16:13:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46798 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730097AbgIHPLM (ORCPT ); Tue, 8 Sep 2020 11:11:12 -0400 Received: from mail-ed1-x543.google.com (mail-ed1-x543.google.com [IPv6:2a00:1450:4864:20::543]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 13416C00459C for ; Tue, 8 Sep 2020 08:09:49 -0700 (PDT) Received: by mail-ed1-x543.google.com with SMTP id l63so16337729edl.9 for ; Tue, 08 Sep 2020 08:09:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=qeNAwf96U+vrersmX6/zX5LAcMEPOlKjRQFFX9HVgVo=; b=d04XD4wuGYZKDFoeUGggqqzXwzd0VsEDo6lGpROBTOkED3kJI1+94j6ITiYOUVrlW7 un4Fs5b6mF3ge0DnXus6rBSJM+U7qyxKRB+WD9TCYpPVeq9KHU6VzdHDzX6axffUg1Ze tNgxHZmOUVWjGOubJIYSMS3BHyReZG57/KUfM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=qeNAwf96U+vrersmX6/zX5LAcMEPOlKjRQFFX9HVgVo=; b=Y8y4v959CqqzxXF1zix5kzcRbBmzbwptWb3oJBGtqaCie3iUG0wKlcXl7HsdYuGjz0 EjzipahzJ9wecMj1AG/ItFsXwK9bXYbM+ZI6YQDZ5CrSrZATeeX70bdhfoQgh0ZiUv2q AZwPvcL8WeB+YdArcAS1NAYa5mzfI5Z9XrdlJgOStZYmQtB35dnHCMrfmvYlD4AweiCG Ip22WaV7d9Cl8AbrBi7h4es+rg7+QS2OguU75zxCdavp/QqX3cNjfowaHxH3sAau7joz gzfgSaPtyYuyKggwrrrDfDIeXfsYWq6vF2+DDR8ievmGjYZzIQatgadPl6Z8kLGJIyeH rb0Q== X-Gm-Message-State: AOAM531JEQpAglYBoPHs0VD3KkMPtgcThw+i4iHtHfrR2fWJnrMtcLZB dgpQQ7/RfcuQn4LeHIz047FQrw== X-Google-Smtp-Source: ABdhPJxDBr5+O5eYvDzGM29LFm9OajpzqSaZp8GDx0Q2+MDUSqtVvvBDLIIVW9I+DX7jhLkjasC/qQ== X-Received: by 2002:a05:6402:615:: with SMTP id n21mr26220771edv.59.1599577786255; Tue, 08 Sep 2020 08:09:46 -0700 (PDT) Received: from localhost ([2620:10d:c093:400::5:4614]) by smtp.gmail.com with ESMTPSA id y21sm6926839eju.46.2020.09.08.08.09.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Sep 2020 08:09:45 -0700 (PDT) Date: Tue, 8 Sep 2020 16:09:45 +0100 From: Chris Down To: zangchunxin@bytedance.com Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song Subject: Re: [PATCH] mm/vmscan: fix infinite loop in drop_slab_node Message-ID: <20200908150945.GA1301981@chrisdown.name> References: <20200908142456.89626-1-zangchunxin@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20200908142456.89626-1-zangchunxin@bytedance.com> User-Agent: Mutt/1.14.6 (2020-07-11) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org drop_caches by its very nature can be extremely performance intensive -- if someone wants to abort after trying too long, they can just send a TASK_KILLABLE signal, no? If exiting the loop and returning to usermode doesn't reliably work when doing that, then _that's_ something to improve, but this looks premature to me until that's demonstrated not to work. zangchunxin@bytedance.com writes: >In one drop caches action, only traverse memcg once maybe is better. >If user need more memory, they can do drop caches again. Can you please provide some measurements of the difference in reclamation in practice?