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[2003:cb:c707:3900:757e:83f8:a99d:41ae]) by smtp.gmail.com with ESMTPSA id n16-20020a1c7210000000b003f19b3d89e9sm2903695wmc.33.2023.05.17.11.32.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 May 2023 11:32:52 -0700 (PDT) Message-ID: Date: Wed, 17 May 2023 20:32:51 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 To: Khalid Aziz , akpm@linux-foundation.org Cc: willy@infradead.org, steven.sistare@oracle.com, ying.huang@intel.com, mgorman@techsingularity.net, khalid@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230517161555.84776-1-khalid.aziz@oracle.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v3] mm, compaction: Skip all non-migratable pages during scan In-Reply-To: <20230517161555.84776-1-khalid.aziz@oracle.com> 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-Stat-Signature: jhnx16eg7pkkn8iicb36r57qdfo5r8ku X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 831E0140022 X-Rspam-User: X-HE-Tag: 1684348376-407965 X-HE-Meta: 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 vGbYE0CK V/mDb7HkpaJtQhPvBc8a4GxOEgNTXsrHwPX/3mkgxmEpqULbj3IOU0sohvWWNZs7dl/10vPriNI/Cz6L6FwK6Zj44R5OczZOoGedeQLGqw2XFaWBk6IRUuxqXe66EzOpOxw6worOTCQWiWVTT5EApTWe9NrzeIwDijIjqRIW4X6NL0gkuv+AAFEDnBe+4Zm1FSZcJzvhReCKou6gfwHEXGDtI6nlsrRYtF4bLiJbBKepPjhdm1nukhEoBmDqJeHg4YQKc80VnhPFWDgOEb7QdjuG5axbfi+JuFE/LHAF9v33T7JE0goLibzm4rrLBy5aiS7tu+jljgloS18bUMUmSxwLN7LBtcAZZqwCTRo5RvccogT2UKKuJzbqHy30DHIkzBufn X-Bogosity: Ham, tests=bogofilter, spamicity=0.000006, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 17.05.23 18:15, Khalid Aziz wrote: > Pages pinned in memory through extra refcounts can not be migrated. > Currently as isolate_migratepages_block() scans pages for > compaction, it skips any pinned anonymous pages. All non-migratable > pages should be skipped and not just the anonymous pinned pages. > This patch adds a check for extra refcounts on a page to determine > if the page can be migrated. This was seen as a real issue on a > customer workload where a large number of pages were pinned by vfio > on the host and any attempts to allocate hugepages resulted in > significant amount of cpu time spent in either direct compaction or > in kcompactd scanning vfio pinned pages over and over again that can > not be migrated. How will this change affect alloc_contig_range(), such as used for CMA allocations or virtio-mem? alloc_contig_range() ends up calling isolate_migratepages_range() -> isolate_migratepages_block(). We don't want to fail early in case there is a short-term pin that might go away any moment after we isolated ... that will make the situation worse for these use cases, especially if MIGRATE_CMA or ZONE_MOVABLE is involved. -- Thanks, David / dhildenb