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[209.85.220.65]) by mx.google.com with SMTPS id b75sor4479034ywa.115.2019.01.28.13.31.20 for (Google Transport Security); Mon, 28 Jan 2019 13:31:20 -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=ZEOZkIB1; 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=YAmmgKNRrQc5gbyA9vCwhi1X0/D3dSvcMoWevldO61g=; b=ZEOZkIB1dewlaD5Y88LebQn5HMgZEDeuALlgAC8pDnS/sfQZ8K6q8lkY836iFp/Kdw 1It/VXY71UBzl1Bq7uh1IQfoJmSOqpgULvqmJE3ZspNPl8BPV5sjb83Xb/fC2Mzd/yhA Eu6LIMbmYraCkmEsuq7xjdLo/MM+VJPVxA/A9rZgYLOlqGTs+CVaHhBvXqOFUBWs2gES +xKhaDOu2ZiqRD85iIYTWm8h0IpSudZoXEA+qxmeXddUu0fljZFnNNJvAJjk2cFervnN dFRepVyf/R1qL4CFhy5JHnciEQw4kJrZvH+kb5VjmytlAglZ+q8KE0yqeQQh/uZ4s8Tv og1g== X-Google-Smtp-Source: ALg8bN7r2Al7asGW6bKrsfih1TF2sfeDStiKF6KOaXlnpYSIXwhcAGaYJxIlng3sTi0ucBCqmjkmxQ== X-Received: by 2002:a81:11d5:: with SMTP id 204mr22836937ywr.287.1548711079931; Mon, 28 Jan 2019 13:31:19 -0800 (PST) Received: from localhost ([2620:10d:c091:200::5:42c8]) by smtp.gmail.com with ESMTPSA id p3sm12266647ywc.14.2019.01.28.13.31.18 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 28 Jan 2019 13:31:19 -0800 (PST) Date: Mon, 28 Jan 2019 16:31:18 -0500 From: Johannes Weiner To: Rik van Riel Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@fb.com, Chris Mason , Roman Gushchin , Andrew Morton , Michal Hocko Subject: Re: [PATCH] mm,slab,vmscan: accumulate gradual pressure on small slabs Message-ID: <20190128213118.GE1416@cmpxchg.org> References: <20190128143535.7767c397@imladris.surriel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190128143535.7767c397@imladris.surriel.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 Mon, Jan 28, 2019 at 02:35:35PM -0500, Rik van Riel wrote: > There are a few issues with the way the number of slab objects to > scan is calculated in do_shrink_slab. First, for zero-seek slabs, > we could leave the last object around forever. That could result > in pinning a dying cgroup into memory, instead of reclaiming it. > The fix for that is trivial. > > Secondly, small slabs receive much more pressure, relative to their > size, than larger slabs, due to "rounding up" the minimum number of > scanned objects to batch_size. > > We can keep the pressure on all slabs equal relative to their size > by accumulating the scan pressure on small slabs over time, resulting > in sometimes scanning an object, instead of always scanning several. > > This results in lower system CPU use, and a lower major fault rate, > as actively used entries from smaller caches get reclaimed less > aggressively, and need to be reloaded/recreated less often. > > Fixes: 4b85afbdacd2 ("mm: zero-seek shrinkers") > Fixes: 172b06c32b94 ("mm: slowly shrink slabs with a relatively small number of objects") > Cc: Johannes Weiner > Cc: Chris Mason > Cc: Roman Gushchin > Cc: kernel-team@fb.com > Tested-by: Chris Mason Acked-by: Johannes Weiner