From: Mel Gorman <firstname.lastname@example.org> To: Linux-MM <email@example.com> Cc: Dave Hansen <firstname.lastname@example.org>, Matthew Wilcox <email@example.com>, Vlastimil Babka <firstname.lastname@example.org>, Michal Hocko <email@example.com>, Nicholas Piggin <firstname.lastname@example.org>, LKML <email@example.com>, Mel Gorman <firstname.lastname@example.org> Subject: [RFC PATCH 0/6] Calculate pcp->high based on zone sizes and active CPUs Date: Fri, 21 May 2021 11:28:20 +0100 [thread overview] Message-ID: <email@example.com> (raw) The per-cpu page allocator (PCP) is meant to reduce contention on the zone lock but the sizing of batch and high is archaic and neither takes the zone size into account or the number of CPUs local to a zone. Furthermore, the fact that vm.percpu_pagelist_fraction adjusts both batch and high values means that the sysctl can reduce zone lock contention but also increase allocation latencies. This series disassociates pcp->high from pcp->batch and then scales pcp->high based on the size of the local zone with limited impact to reclaim and accounting for active CPUs but leaves pcp->batch static. It also adapts the number of pages that can be on the pcp list based on recent freeing patterns. The motivation is partially to adjust to larger memory sizes but is also driven by the fact that large batches of page freeing via release_pages() often shows zone contention as a major part of the problem. Another is a bug report based on an older kernel where a multi-terabyte process can takes several minutes to exit. A workaround was to use vm.percpu_pagelist_fraction to increase the pcp->high value but testing indicated that a production workload could not use the same values because of an increase in allocation latencies. Unfortunately, I cannot reproduce this test case myself as the multi-terabyte machines are in active use but it should alleviate the problem. The series aims to address both and partially acts as a pre-requisite. pcp only works with order-0 which is useless for SLUB (when using high orders) and THP (unconditionally). To store high-order pages on PCP, the pcp->high values need to be increased first. Documentation/admin-guide/sysctl/vm.rst | 19 +-- include/linux/cpuhotplug.h | 2 +- include/linux/mmzone.h | 8 +- kernel/sysctl.c | 8 +- mm/internal.h | 2 +- mm/memory_hotplug.c | 4 +- mm/page_alloc.c | 166 +++++++++++++++++------- mm/vmscan.c | 35 +++++ 8 files changed, 179 insertions(+), 65 deletions(-) -- 2.26.2
next reply other threads:[~2021-05-21 10:30 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-21 10:28 Mel Gorman [this message] 2021-05-21 10:28 ` [PATCH 1/6] mm/page_alloc: Delete vm.percpu_pagelist_fraction Mel Gorman 2021-05-21 21:04 ` Dave Hansen 2021-05-21 10:28 ` [PATCH 2/6] mm/page_alloc: Disassociate the pcp->high from pcp->batch Mel Gorman 2021-05-21 21:52 ` Dave Hansen 2021-05-24 8:32 ` Mel Gorman 2021-05-21 10:28 ` [PATCH 3/6] mm/page_alloc: Adjust pcp->high after CPU hotplug events Mel Gorman 2021-05-21 22:13 ` Dave Hansen 2021-05-24 9:07 ` Mel Gorman 2021-05-24 15:52 ` Dave Hansen 2021-05-24 16:01 ` Mel Gorman 2021-05-21 10:28 ` [PATCH 4/6] mm/page_alloc: Scale the number of pages that are batch freed Mel Gorman 2021-05-21 22:36 ` Dave Hansen 2021-05-24 9:12 ` Mel Gorman 2021-05-21 10:28 ` [PATCH 5/6] mm/page_alloc: Limit the number of pages on PCP lists when reclaim is active Mel Gorman 2021-05-21 22:44 ` Dave Hansen 2021-05-24 9:22 ` Mel Gorman 2021-05-21 10:28 ` [PATCH 6/6] mm/page_alloc: Introduce vm.percpu_pagelist_high_fraction Mel Gorman 2021-05-21 22:57 ` Dave Hansen 2021-05-24 9:25 ` Mel Gorman
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