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=-5.5 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT 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 22906C282C7 for ; Tue, 29 Jan 2019 22:53:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DEC3420882 for ; Tue, 29 Jan 2019 22:53:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cmpxchg-org.20150623.gappssmtp.com header.i=@cmpxchg-org.20150623.gappssmtp.com header.b="v+IFQX2U" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729790AbfA2WxU (ORCPT ); Tue, 29 Jan 2019 17:53:20 -0500 Received: from mail-yb1-f194.google.com ([209.85.219.194]:33715 "EHLO mail-yb1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727980AbfA2WxU (ORCPT ); Tue, 29 Jan 2019 17:53:20 -0500 Received: by mail-yb1-f194.google.com with SMTP id m132so7149858ybf.0 for ; Tue, 29 Jan 2019 14:53:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=6MYSIu9/mxSgvVDzeyAbkyzekemqllHuVnpF2mA9+JM=; b=v+IFQX2U1tBEJewgmJ5IQT8W9FVVwF+gS7oR55ixFbJeRF7KjjVOIbSTaW7vfyuyX+ zjFJZOO5EVvQvAgZq7GTtAbi0SAPexF0xlpZ6/EkDeSTVwEwCJbwJvuChhXGZyxXx7vF 0dBbo5wjw63dB2MMh2qwuwVBr0sPkXb7FxDG3gSVDAH7KbVN/bidpdIcXP6Og7YT4RwX 3Gqzd7Y2Oj67G1PqpHGsGFMkTX+1a39TtEAxbsSC4uXztAb1AfZpEq50Ctpy8pToLNXo 5KJq3QATze1/eg2Cs5FVThUAYi3WQZTiw96tjPiVav6ClaDAcyEhrbvtPO2Flm0ZWYb5 54Qw== 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=6MYSIu9/mxSgvVDzeyAbkyzekemqllHuVnpF2mA9+JM=; b=QdvkHOKSKEzcM4C1lftjjm8xQxJxj2Bh+b1S9nZa7Ws3pVBqP4EkLIaVAuKp4NzcLF JPBUDEr22Tct7fJXBLF6OlXIDRto8ju3gt3g9lx1Uv/OWGqunBGK/VX9ytl+hgqLmYK/ 55w0uhIsOOBSsZlNCmeynH+GIH9QAiErioPgqjRezFsSyVN/f7EvFs2aAERrHA+3jSw5 Tnknyb/ZXzYJOLEoBkzT4zyk1uKBKvTit3ROcXIFsov3qqRrPXSukyt+B1vrJXWd8lWN C5MK6oIY5S3T1+BZk+7BK/y+dJJjsTROjfyBh1k1MVs5R7i3TpHDsPaofZ00BE6Jh8/h ywqA== X-Gm-Message-State: AHQUAuYClHuHI2Hvk8vfxCQ8Rl712y2/sNDu1Pp8nbKaMt6GLctKTZLm wg07OUqh+KVfDtP2kXIaWXkJZb1lOzU= X-Google-Smtp-Source: AHgI3IbQOkhPGIi2VDq4AzAvBM7PZMZp6f/mE9dZqw4Ul4vZAEUBaNyh9TTj+V1JCKaR6Z0f3mMHoA== X-Received: by 2002:a25:db06:: with SMTP id g6mr10082131ybf.498.1548802399444; Tue, 29 Jan 2019 14:53:19 -0800 (PST) Received: from localhost ([2620:10d:c091:200::4:1d25]) by smtp.gmail.com with ESMTPSA id n16sm18580765ywn.31.2019.01.29.14.53.18 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 29 Jan 2019 14:53:18 -0800 (PST) Date: Tue, 29 Jan 2019 17:53:17 -0500 From: Johannes Weiner To: Yang Shi Cc: mhocko@suse.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC v2 PATCH] mm: vmscan: do not iterate all mem cgroups for global direct reclaim Message-ID: <20190129225317.GA15515@cmpxchg.org> References: <1548799877-10949-1-git-send-email-yang.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1548799877-10949-1-git-send-email-yang.shi@linux.alibaba.com> User-Agent: Mutt/1.11.2 (2019-01-07) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 30, 2019 at 06:11:17AM +0800, Yang Shi wrote: > In current implementation, both kswapd and direct reclaim has to iterate > all mem cgroups. It is not a problem before offline mem cgroups could > be iterated. But, currently with iterating offline mem cgroups, it > could be very time consuming. In our workloads, we saw over 400K mem > cgroups accumulated in some cases, only a few hundred are online memcgs. > Although kswapd could help out to reduce the number of memcgs, direct > reclaim still get hit with iterating a number of offline memcgs in some > cases. We experienced the responsiveness problems due to this > occassionally. > > A simple test with pref shows it may take around 220ms to iterate 8K memcgs > in direct reclaim: > dd 13873 [011] 578.542919: vmscan:mm_vmscan_direct_reclaim_begin > dd 13873 [011] 578.758689: vmscan:mm_vmscan_direct_reclaim_end > So for 400K, it may take around 11 seconds to iterate all memcgs. > > Here just break the iteration once it reclaims enough pages as what > memcg direct reclaim does. This may hurt the fairness among memcgs. But > the cached iterator cookie could help to achieve the fairness more or > less. > > Cc: Johannes Weiner > Cc: Michal Hocko > Signed-off-by: Yang Shi Looks sane to me, thanks Yang. Acked-by: Johannes Weiner