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Mon, 25 Mar 2024 15:30:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id tpATGauYAWbNOgAAn2gu4w (envelope-from ); Mon, 25 Mar 2024 15:30:51 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 08088A0812; Mon, 25 Mar 2024 16:30:47 +0100 (CET) Date: Mon, 25 Mar 2024 16:30:46 +0100 From: Jan Kara To: Liu Shixin Cc: Jan Kara , Matthew Wilcox , Andrew Morton , Alexander Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 2/2] mm/readahead: don't decrease mmap_miss when folio has workingset flags Message-ID: <20240325153046.5m5xls7emjfa45da@quack3> References: <20240322093555.226789-1-liushixin2@huawei.com> <20240322093555.226789-3-liushixin2@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240322093555.226789-3-liushixin2@huawei.com> X-Stat-Signature: jjjfsyejrdshzef99khc8ii7yokx9oo9 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 73647140024 X-Rspam-User: X-HE-Tag: 1711380653-114379 X-HE-Meta: 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 UTZmVt+c LceHK5wLcceKnjPQl71Sk+yDRigDiayVauZ3g033HrJhFRWnEnq8apVUK1O7CtNpRYqwzbQecULxkLzIVeq8+BE2srMq0mLNC7LSAqP9DQ29K8oQGaO8lmOPx8cFO6LlQXCG+l+Gfjnf6BUd+wIhaeVxY8mW1JQCI7ebyXcbHKSS6up8RdjlyzLQjt+E121PiJbYJx+2pRBxJwJioMq/Fr1MtiiziyZ8MJRPtDp16EGMjgaWs7WqoAnmEQRh6Qq9J0Hg82xuPYLhpOSCrCryTAI1FcfP4KRmKZGyxqIV3DU9+PHQUls0+pv2FkVQjXe2Culwjoe8vDj/jlvM8Z7Zsf1TCrNbPq6pSaJR6 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: List-Subscribe: List-Unsubscribe: On Fri 22-03-24 17:35:55, Liu Shixin wrote: > If there are too many folios that are recently evicted in a file, then > they will probably continue to be evicted. In such situation, there is > no positive effect to read-ahead this file since it is only a waste of IO. > > The mmap_miss is increased in do_sync_mmap_readahead() and decreased in > both do_async_mmap_readahead() and filemap_map_pages(). In order to skip > read-ahead in above scenario, the mmap_miss have to increased exceed > MMAP_LOTSAMISS. This can be done by stop decreased mmap_miss when folio > has workingset flags. The async path is not to care because in above > scenario, it's hard to run into the async path. > > Signed-off-by: Liu Shixin ... > diff --git a/mm/filemap.c b/mm/filemap.c > index 8df4797c5287..753771310127 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -3439,7 +3439,8 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf, > if (PageHWPoison(page + count)) > goto skip; > > - (*mmap_miss)++; > + if (!folio_test_workingset(folio)) > + (*mmap_miss)++; Hum, so this means we consider this a 'hit' if the page is completely new in the page cache or evicted long time ago. OK, makes sense. It would be nice to add a comment in this direction to explain the condition. Frankly the whole mmap_miss accounting is broken as I've outlined in my patch series. But I guess this works as a fixup for your immediate problem and we can make mmap_miss accounting sensible later. So for now feel free to add: Reviewed-by: Jan Kara Honza -- Jan Kara SUSE Labs, CR