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[2603:7000:c01:2716:da5e:d3ff:fee7:26e7]) by smtp.gmail.com with ESMTPSA id r10-20020ac85e8a000000b004347d76f43csm2317757qtx.79.2024.04.12.08.11.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Apr 2024 08:11:08 -0700 (PDT) Date: Fri, 12 Apr 2024 11:11:04 -0400 From: Johannes Weiner To: Baolin Wang Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, vbabka@suse.cz, 21cnbao@gmail.com, ryan.roberts@arm.com, david@redhat.com, ying.huang@intel.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: page_alloc: allowing mTHP compaction to capture the freed page directly Message-ID: <20240412151104.GA2955562@cmpxchg.org> References: <8118a5d66a034736a48433beddaca60ed78577c4.1712892329.git.baolin.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8118a5d66a034736a48433beddaca60ed78577c4.1712892329.git.baolin.wang@linux.alibaba.com> X-Rspamd-Queue-Id: 89BBD1C0002 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: xn5pfshep3x4ab6iss1bddg73mk7cs35 X-HE-Tag: 1712934672-377950 X-HE-Meta: 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 GSrehgL+ HHvi5UdFeRGy9MIrwFh0K4umPqWJEPhB7eStLiEa1fgCC86ANsgUPpzBOkqtU3nCBnWLz2ctf6W3TKmHQ/Dwm9l9v28+yFQQMGDaz++dOoGwqCS3cfhlmHpxD6WmwEpzkUVG8CZN+G/frwMvw08yD45HdnuNmfGmN77JwLSondGjz4o76O7qMhn5YS/N/kcFAvWnkME2DwW311SBCP35fUMrC9DHxdwpDxDAgiMJ6Ogweah//cJGftLLdzelHroxJjT2GE/mN1hUtKzrFRfbmqMTgeim/irIjLMvElr7pDAsyrSYAJ3dn9dwzEQfXThazSYKV9lJzLG+11slu6Zgscng+Z2vpXvDrddLm7hIg+hLtJporNmg9AT7PQTVViIpO7tERP+RZHEe10H3rJkc0W73WPX34+PbZTKffxp3ZBaxpxez5NhlDlVsN7tP3Lcrk162XkWIwzaG4vvAnZgo/CQorFVU/N5hxEXan77BH9JRc3XOud44qoARe/JCMhWaZh0kzuIO/sYaAjCY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.193688, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 12, 2024 at 11:27:04AM +0800, Baolin Wang wrote: > Currently, compaction_capture() does not allow lower-order allocations to > directly capture the movable free pages, even though lower-order allocations > might also be requesting movable pages, that can lead to more compaction > scanning. And, with the enablement of mTHP, such situations will become more > common. > > Thus allowing lower-order (mTHP) allocations of movable page types directly > capture the movable free pages can avoid unnecessary compaction scanning, > meanwhile that won't pollute the movable pageblock. With testing 1M mTHP > compaction, it can be seen that compaction scanning is significantly reduced. > > mm-unstable patched > Ops Compaction pages isolated 116598741.00 120946702.00 > Ops Compaction migrate scanned 1764870054.00 1488621550.00 > Ops Compaction free scanned 7707879039.00 4986299318.00 > Ops Compact scan efficiency 22.90 29.85 > Ops Compaction cost 73797.69 72933.48 > > Signed-off-by: Baolin Wang Letting a movable request into a partially compacted movable block seems reasonable. The only advantage of not doing so that I could imagine would be to avoid mixing old with new pages, such that reclaim is more likely to free blocks due to improved LRU grouping. But that seems far-fetched. Notably, __compact_finished() will also stop once the requested MOVABLE order becomes available; so not capturing at that point likely just results in stolen work and compaction restarts. Acked-by: Johannes Weiner