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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id h50sm3328294qte.25.2020.06.03.15.19.56 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Wed, 03 Jun 2020 15:19:58 -0700 (PDT) Date: Wed, 3 Jun 2020 15:19:42 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Matthew Wilcox cc: Hugh Dickins , Johannes Weiner , Andrew Morton , Song Liu , "Kirill A. Shutemov" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm,thp: stop leaking unreleased file pages In-Reply-To: <20200603215122.GR19604@bombadil.infradead.org> Message-ID: References: <20200526160140.GC850116@cmpxchg.org> <20200603215122.GR19604@bombadil.infradead.org> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Rspamd-Queue-Id: 33437180D0180 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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, 3 Jun 2020, Matthew Wilcox wrote: > On Wed, May 27, 2020 at 02:28:10PM -0700, Hugh Dickins wrote: > > Saying "source inspection" reminds me: there is another funny in there, > > but I don't think it matters very much in practice, and might need > > rather a lot of testing to justify any particular patch: where > > page_cache_sync_readahead() asks for PAGE_SIZE pages! > > > > "end - index" seems a more reasonable number to me: but then we > > might find that reading ahead into the next huge extent had actually > > been a useful optimization (and those readahead functions impose > > their own caps, so PAGE_SIZE shouldn't work out too outrageously). > > That readahead was only added in 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 > so it probably hasn't really been performance tested yet. I can well imagine that an entirely new body of code, exercised in the background by khugepaged, will not be a leading candidate for performance comparisons - rightly so; but arguing that by the commit being in the tree for only eight months seems... odd :) Hugh