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[209.85.220.65]) by mx.google.com with SMTPS id r27sor13135875pfq.73.2019.07.17.10.53.22 for (Google Transport Security); Wed, 17 Jul 2019 10:53:22 -0700 (PDT) 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=PicqJS4o; 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=z2SSmhd68h87dQhwvWTjUlLYyoXB//o48emXKDITCxQ=; b=PicqJS4oQ5peSgXROAA8eXF277L4r7XmQo7cZukrfLSYdqLgbwsEd5Dqzk8QpxK7iV Jr7zEtrtR7thmPO+J1QqTaT3j+I0++ACo6TT6aLs2O6D/+ubRqwsDUj8iqkYUHlSu3uP S2KX/7zlhOpvgyqTAThJQxGs1jnQy4eGdv0gbpjnWh/cRorbYj9HH98ccTyznWgcEXac q+hc0yDQCCnUJLqZHjU4NiRzAjIzNBE+SyaYhXxaMZoParySRgAtaVZmE7db4nbJWShy 2wprrKIAvpplpmvdMXRr1OD5xBE/XjJHL4qajuxjvrPz4tpMfAgYgXaVJxT7SoPPfBK0 oskQ== X-Google-Smtp-Source: APXvYqws5y1Y3Qi2XGvjYV4PuosbGfC72ojawETni+lagfagIVzMSmpCmtv3mdSH5rkpTds+RX2eng== X-Received: by 2002:a65:4d4e:: with SMTP id j14mr42320858pgt.50.1563386002312; Wed, 17 Jul 2019 10:53:22 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::3:4db]) by smtp.gmail.com with ESMTPSA id b26sm29434788pfo.129.2019.07.17.10.53.20 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 17 Jul 2019 10:53:21 -0700 (PDT) Date: Wed, 17 Jul 2019 13:53:19 -0400 From: Johannes Weiner To: Konstantin Khlebnikov Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko Subject: Re: [PATCH 2/2] mm/memcontrol: split local and nested atomic vmstats/vmevents counters Message-ID: <20190717175319.GB25882@cmpxchg.org> References: <156336655741.2828.4721531901883313745.stgit@buzz> <156336655979.2828.15196553724473875230.stgit@buzz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <156336655979.2828.15196553724473875230.stgit@buzz> User-Agent: Mutt/1.12.0 (2019-05-25) 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, Jul 17, 2019 at 03:29:19PM +0300, Konstantin Khlebnikov wrote: > This is alternative solution for problem addressed in commit 815744d75152 > ("mm: memcontrol: don't batch updates of local VM stats and events"). > > Instead of adding second set of percpu counters which wastes memory and > slows down showing statistics in cgroup-v1 this patch use two arrays of > atomic counters: local and nested statistics. > > Then update has the same amount of atomic operations: local update and > one nested for each parent cgroup. Readers of hierarchical statistics > have to sum two atomics which isn't a big deal. > > All updates are still batched using one set of percpu counters. > > Signed-off-by: Konstantin Khlebnikov Yeah that looks better. Note that it was never about the atomics, though, but rather the number of cachelines dirtied. Your patch should solve this problem as well, but it might be a good idea to run will-it-scale on it to make sure the struct layout is still fine.