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[209.85.220.65]) by mx.google.com with SMTPS id d126sor3411778ybh.195.2019.01.29.14.53.19 for (Google Transport Security); Tue, 29 Jan 2019 14:53:19 -0800 (PST) Received-SPF: pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@cmpxchg-org.20150623.gappssmtp.com header.s=20150623 header.b=v+IFQX2U; spf=pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=cmpxchg.org 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-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) 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: 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