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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1q2kRT-003TLK-ER; Sat, 27 May 2023 03:18:07 +0000 Date: Sat, 27 May 2023 04:18:07 +0100 From: Matthew Wilcox To: John Hubbard Cc: David Hildenbrand , Khalid Aziz , Steven Sistare , akpm@linux-foundation.org, ying.huang@intel.com, mgorman@techsingularity.net, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Khalid Aziz Subject: Re: [PATCH v4] mm, compaction: Skip all non-migratable pages during scan Message-ID: References: <60367660-f4a3-06dc-4d17-4dbdc733ef74@oracle.com> <846b770c-9f63-90a2-0435-ec82484e3f74@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <846b770c-9f63-90a2-0435-ec82484e3f74@nvidia.com> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 6AC8C40005 X-Stat-Signature: 6cy8tpcct919gx86c7ukta3qfbsykema X-HE-Tag: 1685157510-600449 X-HE-Meta: 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 8pkp1EWt fu0oiAGCwi1PQLwoLtuV9TW9UQTWwqmoi9/vpgVEp0QbVFWhQn9n2n3yjjxhNUpLQF51dtbkJpxL4sL6cynlCaZeNxj6DerqAtI7WfdIc2ZlRkwaJiwHxNhij0PDiPpY+tif9gntU4motzB0= 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 Fri, May 26, 2023 at 07:11:05PM -0700, John Hubbard wrote: > > So any user with 1024 processes can fragment physical memory? :/ > > > > Sorry, I'd like to minimize the usage of folio_maybe_dma_pinned(). > > I was actually thinking that we should minimize any more cases of > fragile mapcount and refcount comparison, which then leads to > Matthew's approach here! I was wondering if we shouldn't make folio_maybe_dma_pinned() a little more accurate. eg: if (folio_test_large(folio)) return atomic_read(&folio->_pincount) > 0; return (unsigned)(folio_ref_count(folio) - folio_mapcount(folio)) >= GUP_PIN_COUNTING_BIAS;