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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qLQAi-0042X2-Gl; Mon, 17 Jul 2023 15:30:00 +0000 Date: Mon, 17 Jul 2023 16:30:00 +0100 From: Matthew Wilcox To: Ryan Roberts Cc: Andrew Morton , Yin Fengwei , David Hildenbrand , Yu Zhao , Yang Shi , "Huang, Ying" , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v1 1/3] mm: Allow deferred splitting of arbitrary large anon folios Message-ID: References: <20230717143110.260162-1-ryan.roberts@arm.com> <20230717143110.260162-2-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230717143110.260162-2-ryan.roberts@arm.com> X-Stat-Signature: 63oakt5m5suge38bzhxtgq8q13fnk9jr X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 004924001C X-Rspam-User: X-HE-Tag: 1689607813-118655 X-HE-Meta: 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 FmU6qZ0W MVS3bdtMxZweDI0Eq+90EbEBsFiHTKVaTEPwgn3IuCO8vaSiX15XoBmniOalNKPoOkPhwJuG5YisGZFDwHEplgKWsYmztwEwppxKLyRBwwWTrWBLGld8HrCmqFP6ZDA1t2lT72B3PYUIfx3LkIlJ8jxEIjJ5yNOWwuz9lM4vI2ICiNvgvd4MBFaLaAkOzy10E1X6l0SLV1VjaaobBQaIHm82PAB/SaB4Q3qAbcHoUxi67JQfAK3KeDWHm05pho3F4cU4Qlq80+nT9/9J91kMdeHBwVY5KfIaze/0t5ZmzFE2Ost8= 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, Jul 17, 2023 at 03:31:08PM +0100, Ryan Roberts wrote: > In preparation for the introduction of large folios for anonymous > memory, we would like to be able to split them when they have unmapped > subpages, in order to free those unused pages under memory pressure. So > remove the artificial requirement that the large folio needed to be at > least PMD-sized. > > Signed-off-by: Ryan Roberts > Reviewed-by: Yu Zhao > Reviewed-by: Yin Fengwei Reviewed-by: Matthew Wilcox (Oracle) > */ > - if (folio_test_pmd_mappable(folio) && folio_test_anon(folio)) > + if (folio_test_large(folio) && folio_test_anon(folio)) > if (!compound || nr < nr_pmdmapped) > deferred_split_folio(folio); I wonder if it's worth introducing a folio_test_deferred_split() (better naming appreciated ...) to allow us to allocate order-1 folios and not do horrible things. Maybe it's not worth supporting order-1 folios; we're always better off going to order-2 immediately. Just thinking.