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s=korg; t=1686348673; bh=lffJYaMQAt9WPAdTp1t2dEqqXehvGeWl0jgqeQiZLsI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=veolEzIkoNAhgbTjDkz+B4HaCTlVkq0cOqTDiKJoT3tbi2byP08KumyaxKPbusMxn zaq9ENZkZOEQ15ayq670UoLBmJBtHeAAgxt6J3b/dRk+TDT+r14OKJV91mfPXEFwEV dHDceG0/cT+PDUwfxP4UymV3WPb8PpdO8x7N34JY= Date: Fri, 9 Jun 2023 15:11:11 -0700 From: Andrew Morton To: Khalid Aziz Cc: David Hildenbrand , Matthew Wilcox , John Hubbard , Steven Sistare , 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: <20230609151111.bb7908254853a0879db07746@linux-foundation.org> In-Reply-To: <3c2ac70b-31a2-4e85-0ade-cb9f701525b3@oracle.com> References: <60367660-f4a3-06dc-4d17-4dbdc733ef74@oracle.com> <846b770c-9f63-90a2-0435-ec82484e3f74@nvidia.com> <9821bd9c-7c30-8f0c-68e4-6b1d312bc032@nvidia.com> <4d035744-271d-1ca3-a440-f8b1573eec96@redhat.com> <3c2ac70b-31a2-4e85-0ade-cb9f701525b3@oracle.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: A12A42000C X-Stat-Signature: yk7aaf76xd8i4m7xqxk1oufi7493sx3g X-HE-Tag: 1686348674-385678 X-HE-Meta: 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 476C5hBi 6QtVjDEoScPWoZOQOV3msJuu/JFhG4MlZ/AxQNPE6PXG70vqOmM5CEbshlfz7W9JOKxDtyKeWwcDcLDea0JUX1z/Cm1m2slE4+fLqP0WX67oWFUOzY7Zvh3/oAoUwjHZjPpZwmjbYNikYwKho1soeKj/RMhUFRWiEYxTEoQsdzn6ZaOMxAxahvTVdrHgiKt9rjOJgFl2q0SSACg73Cik/5s8E9U/+Bm4Zgd/MyXyyja7K1gIA76SW7pMfpdG3CNvzGC+1DLV0fWCah09pOEQkZ499J9KOShVhCg8HNwMLe6Cd6X1wVzWHM3zUY0/DwTh7SlIGMIT31t1X8mE03L/JhYmKrAjiPVwwdCLl 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 Tue, 30 May 2023 09:42:33 -0600 Khalid Aziz wrote: > > I completely agree that we should be careful with such mapcount vs. pagecount checks, and if we can use something > > better, let's use something *better*. > > When we have a reliable folio_maybe_dma_longterm_pinned() function, it will be better to call that instead of doing > refcount vs mapcount check. Until that better function to check for pinned pages is in place, may I propose that the > current patch fixes a customer problem though not optimally and is a good enough working solution. When a better > function is in place, page_has_extra_refs() function can be updated to rely on this other function instead of refcount > vs mapcount. We seem rather stuck with this patch. I think I'll drop it while we ponder a way forward.