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[2003:d8:2f2e:ae00:f2e3:50e0:73f7:451]) by smtp.gmail.com with ESMTPSA id r14-20020adfce8e000000b00307925ff35bsm5571809wrn.49.2023.05.26.09.46.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 May 2023 09:46:16 -0700 (PDT) Message-ID: Date: Fri, 26 May 2023 18:46:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v4] mm, compaction: Skip all non-migratable pages during scan To: Matthew Wilcox , Khalid Aziz Cc: 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 References: <20230525191507.160076-1-khalid.aziz@oracle.com> <60367660-f4a3-06dc-4d17-4dbdc733ef74@oracle.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 0FAF4180019 X-Stat-Signature: brshpnmb3fsz3qrgcad13ig687xgna3n X-HE-Tag: 1685119581-437674 X-HE-Meta: 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 Jd3LdzfH rVhVGFFqrB/85IADFETquwCFWgqBehLrR0FyypR9e9XD+mnnz1wRndas4SwHh/5eiYPy3MpVcUxMaUaARmrXLWdpDVVgkvDhcTdcX6W16KGmn9IvG6uj7ixMCV3Wj9eYL+cAoT99WDavQuOQALcrH//BmV5/NvM/bUdLPQnfLUuIgFEXjxurECrgox0g+Q5gYMks8t7tImDxgDij9IwuGVRKO4fWfiCAlm2uei3bLReklkkIEyJvBn1zsBMrE/6Pd/2UO/030JtsXAEdsWj6I7tW/ljMeJo0e3wxenk0zjtuP/jwKYKwme3fXY9FqHDekFbjPoYkglbebHY/V7zEd3Ez6CQCSsFmHtyfxFUXnf2lyTryaC4mE7ogYEuou5Lz+vGBp 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 26.05.23 18:44, Matthew Wilcox wrote: > On Fri, May 26, 2023 at 09:44:34AM -0600, Khalid Aziz wrote: >>> Oh, I think I found it! pin_user_pages_remote() is called by >>> vaddr_get_pfns(). If these are the pages you're concerned about, >>> then the efficient way to do what you want is simply to call >>> folio_maybe_dma_pinned(). Far more efficient than the current mess >>> of total_mapcount(). >> >> vfio pinned pages triggered this change. Wouldn't checking refcounts against >> mapcount provide a more generalized way of detecting non-migratable pages? > > Well, you changed the comment to say that we were concerned about > long-term pins. If we are, than folio_maybe_dma_pinned() is how to test > for long-term pins. If we want to skip pages which are short-term pinned, > then we need to not change the comment, and keep using mapcount/refcount > differences. > folio_maybe_dma_pinned() is all about FOLL_PIN, not FOLL_LONGTERM. folio_maybe_dma_pinned() would skip migrating any page that has more than 1024 references. (shared libraries?) -- Thanks, David / dhildenb