Re: [PATCH 4/6] mm/page_alloc: Scale the number of pages that are batch freed

[PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Mel Gorman <hidden> · 2021-05-25
[PATCH 2/6] mm/page_alloc: Disassociate the pcp->high from pcp->batch · Mel Gorman <hidden> · 2021-05-25
Re: [PATCH 2/6] mm/page_alloc: Disassociate the pcp->high from pcp->batch · Vlastimil Babka <hidden> · 2021-05-26
Re: [PATCH 2/6] mm/page_alloc: Disassociate the pcp->high from pcp->batch · Mel Gorman <hidden> · 2021-05-27
Re: [PATCH 2/6] mm/page_alloc: Disassociate the pcp->high from pcp->batch · Vlastimil Babka <hidden> · 2021-05-28
[PATCH 3/6] mm/page_alloc: Adjust pcp->high after CPU hotplug events · Mel Gorman <hidden> · 2021-05-25
Re: [PATCH 3/6] mm/page_alloc: Adjust pcp->high after CPU hotplug events · Vlastimil Babka <hidden> · 2021-05-28
[PATCH 5/6] mm/page_alloc: Limit the number of pages on PCP lists when reclaim is active · Mel Gorman <hidden> · 2021-05-25
Re: [PATCH 5/6] mm/page_alloc: Limit the number of pages on PCP lists when reclaim is active · Vlastimil Babka <hidden> · 2021-05-28
[PATCH 1/6] mm/page_alloc: Delete vm.percpu_pagelist_fraction · Mel Gorman <hidden> · 2021-05-25
Re: [PATCH 1/6] mm/page_alloc: Delete vm.percpu_pagelist_fraction · Vlastimil Babka <hidden> · 2021-05-26
[PATCH 6/6] mm/page_alloc: Introduce vm.percpu_pagelist_high_fraction · Mel Gorman <hidden> · 2021-05-25
Re: [PATCH 6/6] mm/page_alloc: Introduce vm.percpu_pagelist_high_fraction · Vlastimil Babka <hidden> · 2021-05-28
Re: [PATCH 6/6] mm/page_alloc: Introduce vm.percpu_pagelist_high_fraction · Mel Gorman <hidden> · 2021-05-28
Re: [PATCH 6/6] mm/page_alloc: Introduce vm.percpu_pagelist_high_fraction · Vlastimil Babka <hidden> · 2021-05-28
[PATCH 4/6] mm/page_alloc: Scale the number of pages that are batch freed · Mel Gorman <hidden> · 2021-05-25
Re: [PATCH 4/6] mm/page_alloc: Scale the number of pages that are batch freed · Vlastimil Babka <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Dave Hansen <hidden> · 2021-05-27
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Mel Gorman <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · David Hildenbrand <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · David Hildenbrand <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Mel Gorman <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · David Hildenbrand <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Mel Gorman <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · David Hildenbrand <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Vlastimil Babka <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Mel Gorman <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Dave Hansen <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Mel Gorman <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Dave Hansen <hidden> · 2021-05-28
Re: [PATCH 0/6 v2] Calculate pcp->high based on zone sizes and active CPUs · Feng Tang <hidden> · 2021-05-31

From: Vlastimil Babka <hidden>
Date: 2021-05-28 11:20:10
Also in: lkml

On 5/25/21 10:01 AM, Mel Gorman wrote:

When a task is freeing a large number of order-0 pages, it may acquire
the zone->lock multiple times freeing pages in batches. This may
unnecessarily contend on the zone lock when freeing very large number
of pages. This patch adapts the size of the batch based on the recent
pattern to scale the batch size for subsequent frees.

As the machines I used were not large enough to test this are not large
enough to illustrate a problem, a debugging patch shows patterns like
the following (slightly editted for clarity)

Baseline vanilla kernel
  time-unmap-14426   [...] free_pcppages_bulk: free   63 count  378 high  378
  time-unmap-14426   [...] free_pcppages_bulk: free   63 count  378 high  378
  time-unmap-14426   [...] free_pcppages_bulk: free   63 count  378 high  378
  time-unmap-14426   [...] free_pcppages_bulk: free   63 count  378 high  378
  time-unmap-14426   [...] free_pcppages_bulk: free   63 count  378 high  378

With patches
  time-unmap-7724    [...] free_pcppages_bulk: free  126 count  814 high  814
  time-unmap-7724    [...] free_pcppages_bulk: free  252 count  814 high  814
  time-unmap-7724    [...] free_pcppages_bulk: free  504 count  814 high  814
  time-unmap-7724    [...] free_pcppages_bulk: free  751 count  814 high  814
  time-unmap-7724    [...] free_pcppages_bulk: free  751 count  814 high  814

Signed-off-by: Mel Gorman <redacted>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>

Acked-by: Vlastimil Babka <redacted>

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