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Tue, 13 Apr 2021 09:13:26 -0700 (PDT) Received: from [192.168.1.30] ([207.135.233.147]) by smtp.gmail.com with ESMTPSA id 3sm2926165ood.46.2021.04.13.09.13.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Apr 2021 09:13:25 -0700 (PDT) Subject: Re: [PATCH v2 00/16] Multigenerational LRU Framework To: SeongJae Park , Yu Zhao Cc: linux-mm@kvack.org, Andi Kleen , Andrew Morton , Benjamin Manes , Dave Chinner , Dave Hansen , Hillf Danton , Johannes Weiner , Jonathan Corbet , Joonsoo Kim , Matthew Wilcox , Mel Gorman , Miaohe Lin , Michael Larabel , Michal Hocko , Michel Lespinasse , Rik van Riel , Roman Gushchin , Rong Chen , SeongJae Park , Tim Chen , Vlastimil Babka , Yang Shi , Ying Huang , Zi Yan , linux-kernel@vger.kernel.org, lkp@lists.01.org, page-reclaim@google.com References: <20210413075155.32652-1-sjpark@amazon.de> From: Jens Axboe Message-ID: <3ddd4f8a-8e51-662b-df11-a63a0e75b2bc@kernel.dk> Date: Tue, 13 Apr 2021 10:13:24 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210413075155.32652-1-sjpark@amazon.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 05F68C0007C2 X-Stat-Signature: d5zc7c7ehsepg5sfomhqywgxyy344fd1 Received-SPF: none (kernel.dk>: No applicable sender policy available) receiver=imf14; identity=mailfrom; envelope-from=""; helo=mail-oi1-f178.google.com; client-ip=209.85.167.178 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618330399-411420 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 4/13/21 1:51 AM, SeongJae Park wrote: > From: SeongJae Park > > Hello, > > > Very interesting work, thank you for sharing this :) > > On Tue, 13 Apr 2021 00:56:17 -0600 Yu Zhao wrote: > >> What's new in v2 >> ================ >> Special thanks to Jens Axboe for reporting a regression in buffered >> I/O and helping test the fix. > > Is the discussion open? If so, could you please give me a link? I wasn't on the initial post (or any of the lists it was posted to), but it's on the google page reclaim list. Not sure if that is public or not. tldr is that I was pretty excited about this work, as buffered IO tends to suck (a lot) for high throughput applications. My test case was pretty simple: Randomly read a fast device, using 4k buffered IO, and watch what happens when the page cache gets filled up. For this particular test, we'll initially be doing 2.1GB/sec of IO, and then drop to 1.5-1.6GB/sec with kswapd using a lot of CPU trying to keep up. That's mainline behavior. The initial posting of this patchset did no better, in fact it did a bit worse. Performance dropped to the same levels and kswapd was using as much CPU as before, but on top of that we also got excessive swapping. Not at a high rate, but 5-10MB/sec continually. I had some back and forths with Yu Zhao and tested a few new revisions, and the current series does much better in this regard. Performance still dips a bit when page cache fills, but not nearly as much, and kswapd is using less CPU than before. Hope that helps, -- Jens Axboe