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Wed, 28 Oct 2020 15:26:39 -0700 (PDT) Subject: Re: + fs-break-generic_file_buffered_read-up-into-multiple-functions.patch added to -mm tree To: Andrew Morton , Matthew Wilcox Cc: linux-mm@kvack.org, kent.overstreet@gmail.com References: <20201025220817.XxXVE%akpm@linux-foundation.org> <20201027133551.GW20115@casper.infradead.org> <20201028152235.125172e46ae70ba4d7094469@linux-foundation.org> From: Jens Axboe Message-ID: Date: Wed, 28 Oct 2020 16:26:38 -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: <20201028152235.125172e46ae70ba4d7094469@linux-foundation.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 10/28/20 4:22 PM, Andrew Morton wrote: > On Tue, 27 Oct 2020 13:35:51 +0000 Matthew Wilcox wrote: > >> On Sun, Oct 25, 2020 at 03:08:17PM -0700, akpm@linux-foundation.org wrote: >>> The patch titled >>> Subject: mm/filemap/c: freak generic_file_buffered_read up into multiple functions >>> has been added to the -mm tree. Its filename is >>> fs-break-generic_file_buffered_read-up-into-multiple-functions.patch >> >> Can we back this out? It really makes the THP patchset unhappy. I think >> we can do something like this afterwards, but doing it this way round is >> ridiculously hard. > > Two concerns: > > : On my test box, 4k buffered random reads go from ~150k to ~250k iops, > : and the improvements to big sequential reads are even bigger. > > That's a big improvement! We want that improvement. Throwing it away > on behalf of an as-yet-unmerged feature patchset hurts. Can we expect that > this improvement will be available post-that-patchset? And when? > > (This improvment is rather hard to believe, really - more details on the > test environment would be useful. Can we expect that people will in > general see similar benefits or was there something special about the > testing?) I did see some wins when I tested this. I'll try and run some testing tomorrow and report back. If there's something specifically you want to see tested, let me know. > Secondly, > > : This incorporates the fix for IOCB_WAITQ handling that Jens just > : posted as well > > Is this (mysterious, unreferenced!) fix against v1 of Kent's patchset, > or is it against mainline? If it's against mainline then it's > presumably first priority. Can we please get that sent out in a > standalone form asap? It's this one: commit 13bd691421bc191a402d2e0d3da5f248d170a632 Author: Jens Axboe Date: Sat Oct 17 08:31:29 2020 -0600 mm: mark async iocb read as NOWAIT once some data has been copied which is in Linus's tree. Kent spotted the issue and had it fixed in his 5.9 based patchset, which is probably where this confusion comes from. -- Jens Axboe