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[2003:cb:c722:9d00:7421:54d8:9227:a3e8]) by smtp.gmail.com with ESMTPSA id c18-20020a7bc852000000b003f4fb5532a1sm1790450wml.43.2023.05.19.02.51.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 19 May 2023 02:51:01 -0700 (PDT) Message-ID: <5f43a17c-94a0-4bff-b451-e5014de36ed9@redhat.com> Date: Fri, 19 May 2023 11:51:00 +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 v3] mm, compaction: Skip all non-migratable pages during scan To: "Huang, Ying" Cc: Khalid Aziz , akpm@linux-foundation.org, willy@infradead.org, steven.sistare@oracle.com, mgorman@techsingularity.net, khalid@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230517161555.84776-1-khalid.aziz@oracle.com> <87sfbubg3j.fsf@yhuang6-desk2.ccr.corp.intel.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <87sfbubg3j.fsf@yhuang6-desk2.ccr.corp.intel.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-Rspamd-Queue-Id: 4C602C0011 X-Rspam-User: X-Stat-Signature: gum9jagf4ye1dkqztx761kgf5airpp4n X-Rspamd-Server: rspam03 X-HE-Tag: 1684489865-90031 X-HE-Meta: U2FsdGVkX18Gy4NaqxSG5W78ktIYCaDbG4okPTiHOqo0vX0oUXMzQ7Yrxe0Sl9y1U6nfn82cbaG94o/xZiL2mXly4TALR9U33f0APyIFUPVQhQmVOIsSKyK33zMve4PVTo5bG7moi6lPJj/0WDO0gyk4HMOizpsZs7u8WzZaudc8YwAaC8AtoVl5Fo/FI28Din//qmYGumXoPihyzJb0mUIo01Hz8tkClYtGrnsUMJaxhA/HYLM1nf2i/3TEgU+VYGOgmiRijRMCAL0I4V6sIQ2wT6xm1cDWCjKB8jePkAsXNg6FaYw32bZRt9RV4KnSyM8EReL9UG3pnRAbCBAZjKkcFteKRD7ThQousJUyOuM6s9LTF4dzmDUzXKipTwqhwv2/OZ28gYaSy+Z5TCU8yKMw+pOUAVQLHFw+uE4dEmKOd9JVB+Wk5La4r25n2/AE40gUOYVrVA1LtGnnjY/6AXa5RmQHY1tnYZLyIij6YiFR7qxYH/ibEbWLN4T7I+SUuRe99Z4wHARGfAxDinG8mGf0QEht1ZObA03G4wCfik+ycxNCG5m36Rbqaz2rdFtqm5nGYTaycZ5Fh6FXcHShUlSzvi3MPDVMZQ8P8qr8FQlwaoliqH5+sWyTsKhC2rabRF3l62jWwbHUx+KlRqx15tXgC/UzThQw2XjPqPXvsymzsfVBTkiGeGfkj1sWwAnTGx9HOemYo24LHQY9Viun/G7iPlb1bvIlzCOMyxE9C9wMjdgAh0f2+NHpJXOpNiCViCmG34TnzyD9jEwirnqcZkDookqkWpF1lQZCwXNKzd3ZDwJVVXL0KS4K8hy0RkHp5zjf0iXd2I5Fzx3RbSTLERpggps7uIcZdIKMIaoSaSQRMoNHLB5S4aYrVqP3B6e3AiT69ffwWqYw150leeUYxAXDytqz4hNfY6+fjeqOcCLh4yteyjc/TpOrR79l0AtDtCbSOaK2gLUBmqdqLe/ ZfkZCHbp kamxwIMl1WV51cTBvlTYEuobsQB6TtNDdo4uonoNow/s+Q3vbdf/jGMWJgDWz7zwJrJ25Fr5yMuFzi9PcoulWRfIwFH6du7TajJq8iFiK7J9i2fpLh66X37CxpHuJNNozercuob8HA8oQvwj0/bxiCSZVlJeSVvCMX66KqQOm8NAMcQ270B1Hhr36pDhSXcdF0uG7/8zrCUEN6vcHrs4/1QJ9zdpl0PkjiVr4MS9HXag3L9EfLSStjB4UeGgBWS0mmIF5NHNXnndXSkNP+Pz0sQaKORVVLcYG7t4G3AoeHuhlpLWO303iByZ9nwqeuIwaThGyALV1bh1cItZQL1mCPxtufecgjJnBNUyZeROPeTl72uD3RjIalw3XcFhycdGg7v6+uoXcUvKoQd8qvoEIgV7pvw== 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 18.05.23 03:09, Huang, Ying wrote: > David Hildenbrand writes: > >> 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(). > > IIUC, cc->alloc_contig can be used to distinguish contiguous allocation > and compaction. And, from the original commit which introduced > anonymous pages skipping (commit 119d6d59dcc0 ("mm, compaction: avoid > isolating pinned pages ")) and this patch, large number of migration > failure during compaction causes real issue too. So, I suggest to use > cc->alloc_contig here. Agreed. I further wonder if we want to special-case the !alloc_contig case also for MIGRATE_CMA and ZONE_MOVABLE, where we cannot have longterm page pinnings (e.g., vfio pinned pages). -- Thanks, David / dhildenb