The patch titled
Subject: mm, page_alloc: only check PageCompound for high-order pages
has been added to the -mm tree. Its filename is
mm-page_alloc-only-check-pagecompound-for-high-order-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-only-check-pagecompound-for-high-order-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-only-check-pagecompound-for-high-order-pages.patch
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------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm, page_alloc: only check PageCompound for high-order pages
Another year, another round of page allocator optimisations focusing this
time on the alloc and free fast paths. This should be of help to
workloads that are allocator-intensive from kernel space where the cost of
zeroing is not nceessraily incurred.
The series is motivated by the observation that page alloc microbenchmarks
on multiple machines regressed between 3.12.44 and 4.4. Second, there is
discussions before LSF/MM considering the possibility of adding another
page allocator which is potentially hazardous but a patch series improving
performance is better than whining.
After the series is applied, there are still hazards. In the free paths,
the debugging checking and page zone/pageblock lookups dominate but there
was not an obvious solution to that. In the alloc path, the major
contributers are dealing with zonelists, new page preperation, the fair
zone allocation and numerous statistic updates. The fair zone allocator
is removed by the per-node LRU series if that gets merged so it's nor a
major concern at the moment.
On normal userspace benchmarks, there is little impact as the zeroing cost
is significant but it's visible
aim9
4.6.0-rc3 4.6.0-rc3
vanilla deferalloc-v3
Min page_test 828693.33 ( 0.00%) 887060.00 ( 7.04%)
Min brk_test 4847266.67 ( 0.00%) 4966266.67 ( 2.45%)
Min exec_test 1271.00 ( 0.00%) 1275.67 ( 0.37%)
Min fork_test 12371.75 ( 0.00%) 12380.00 ( 0.07%)
The overall impact on a page allocator microbenchmark for a range of orders
and number of pages allocated in a batch is
4.6.0-rc3 4.6.0-rc3
vanilla deferalloc-v3r7
Min alloc-odr0-1 428.00 ( 0.00%) 316.00 ( 26.17%)
Min alloc-odr0-2 314.00 ( 0.00%) 231.00 ( 26.43%)
Min alloc-odr0-4 256.00 ( 0.00%) 192.00 ( 25.00%)
Min alloc-odr0-8 222.00 ( 0.00%) 166.00 ( 25.23%)
Min alloc-odr0-16 207.00 ( 0.00%) 154.00 ( 25.60%)
Min alloc-odr0-32 197.00 ( 0.00%) 148.00 ( 24.87%)
Min alloc-odr0-64 193.00 ( 0.00%) 144.00 ( 25.39%)
Min alloc-odr0-128 191.00 ( 0.00%) 143.00 ( 25.13%)
Min alloc-odr0-256 203.00 ( 0.00%) 153.00 ( 24.63%)
Min alloc-odr0-512 212.00 ( 0.00%) 165.00 ( 22.17%)
Min alloc-odr0-1024 221.00 ( 0.00%) 172.00 ( 22.17%)
Min alloc-odr0-2048 225.00 ( 0.00%) 179.00 ( 20.44%)
Min alloc-odr0-4096 232.00 ( 0.00%) 185.00 ( 20.26%)
Min alloc-odr0-8192 235.00 ( 0.00%) 187.00 ( 20.43%)
Min alloc-odr0-16384 236.00 ( 0.00%) 188.00 ( 20.34%)
Min alloc-odr1-1 519.00 ( 0.00%) 450.00 ( 13.29%)
Min alloc-odr1-2 391.00 ( 0.00%) 336.00 ( 14.07%)
Min alloc-odr1-4 313.00 ( 0.00%) 268.00 ( 14.38%)
Min alloc-odr1-8 277.00 ( 0.00%) 235.00 ( 15.16%)
Min alloc-odr1-16 256.00 ( 0.00%) 218.00 ( 14.84%)
Min alloc-odr1-32 252.00 ( 0.00%) 212.00 ( 15.87%)
Min alloc-odr1-64 244.00 ( 0.00%) 206.00 ( 15.57%)
Min alloc-odr1-128 244.00 ( 0.00%) 207.00 ( 15.16%)
Min alloc-odr1-256 243.00 ( 0.00%) 207.00 ( 14.81%)
Min alloc-odr1-512 245.00 ( 0.00%) 209.00 ( 14.69%)
Min alloc-odr1-1024 248.00 ( 0.00%) 214.00 ( 13.71%)
Min alloc-odr1-2048 253.00 ( 0.00%) 220.00 ( 13.04%)
Min alloc-odr1-4096 258.00 ( 0.00%) 224.00 ( 13.18%)
Min alloc-odr1-8192 261.00 ( 0.00%) 229.00 ( 12.26%)
Min alloc-odr2-1 560.00 ( 0.00%) 753.00 (-34.46%)
Min alloc-odr2-2 424.00 ( 0.00%) 351.00 ( 17.22%)
Min alloc-odr2-4 339.00 ( 0.00%) 393.00 (-15.93%)
Min alloc-odr2-8 298.00 ( 0.00%) 246.00 ( 17.45%)
Min alloc-odr2-16 276.00 ( 0.00%) 227.00 ( 17.75%)
Min alloc-odr2-32 271.00 ( 0.00%) 221.00 ( 18.45%)
Min alloc-odr2-64 264.00 ( 0.00%) 217.00 ( 17.80%)
Min alloc-odr2-128 264.00 ( 0.00%) 217.00 ( 17.80%)
Min alloc-odr2-256 264.00 ( 0.00%) 218.00 ( 17.42%)
Min alloc-odr2-512 269.00 ( 0.00%) 223.00 ( 17.10%)
Min alloc-odr2-1024 279.00 ( 0.00%) 230.00 ( 17.56%)
Min alloc-odr2-2048 283.00 ( 0.00%) 235.00 ( 16.96%)
Min alloc-odr2-4096 285.00 ( 0.00%) 239.00 ( 16.14%)
Min alloc-odr3-1 629.00 ( 0.00%) 505.00 ( 19.71%)
Min alloc-odr3-2 472.00 ( 0.00%) 374.00 ( 20.76%)
Min alloc-odr3-4 383.00 ( 0.00%) 301.00 ( 21.41%)
Min alloc-odr3-8 341.00 ( 0.00%) 266.00 ( 21.99%)
Min alloc-odr3-16 316.00 ( 0.00%) 248.00 ( 21.52%)
Min alloc-odr3-32 308.00 ( 0.00%) 241.00 ( 21.75%)
Min alloc-odr3-64 305.00 ( 0.00%) 241.00 ( 20.98%)
Min alloc-odr3-128 308.00 ( 0.00%) 244.00 ( 20.78%)
Min alloc-odr3-256 317.00 ( 0.00%) 249.00 ( 21.45%)
Min alloc-odr3-512 327.00 ( 0.00%) 256.00 ( 21.71%)
Min alloc-odr3-1024 331.00 ( 0.00%) 261.00 ( 21.15%)
Min alloc-odr3-2048 333.00 ( 0.00%) 266.00 ( 20.12%)
Min alloc-odr4-1 767.00 ( 0.00%) 572.00 ( 25.42%)
Min alloc-odr4-2 578.00 ( 0.00%) 429.00 ( 25.78%)
Min alloc-odr4-4 474.00 ( 0.00%) 346.00 ( 27.00%)
Min alloc-odr4-8 422.00 ( 0.00%) 310.00 ( 26.54%)
Min alloc-odr4-16 399.00 ( 0.00%) 295.00 ( 26.07%)
Min alloc-odr4-32 392.00 ( 0.00%) 293.00 ( 25.26%)
Min alloc-odr4-64 394.00 ( 0.00%) 293.00 ( 25.63%)
Min alloc-odr4-128 405.00 ( 0.00%) 305.00 ( 24.69%)
Min alloc-odr4-256 417.00 ( 0.00%) 319.00 ( 23.50%)
Min alloc-odr4-512 425.00 ( 0.00%) 326.00 ( 23.29%)
Min alloc-odr4-1024 426.00 ( 0.00%) 329.00 ( 22.77%)
Min free-odr0-1 216.00 ( 0.00%) 178.00 ( 17.59%)
Min free-odr0-2 152.00 ( 0.00%) 125.00 ( 17.76%)
Min free-odr0-4 120.00 ( 0.00%) 99.00 ( 17.50%)
Min free-odr0-8 106.00 ( 0.00%) 85.00 ( 19.81%)
Min free-odr0-16 97.00 ( 0.00%) 80.00 ( 17.53%)
Min free-odr0-32 92.00 ( 0.00%) 76.00 ( 17.39%)
Min free-odr0-64 89.00 ( 0.00%) 74.00 ( 16.85%)
Min free-odr0-128 89.00 ( 0.00%) 73.00 ( 17.98%)
Min free-odr0-256 107.00 ( 0.00%) 90.00 ( 15.89%)
Min free-odr0-512 117.00 ( 0.00%) 108.00 ( 7.69%)
Min free-odr0-1024 125.00 ( 0.00%) 118.00 ( 5.60%)
Min free-odr0-2048 132.00 ( 0.00%) 125.00 ( 5.30%)
Min free-odr0-4096 135.00 ( 0.00%) 130.00 ( 3.70%)
Min free-odr0-8192 137.00 ( 0.00%) 130.00 ( 5.11%)
Min free-odr0-16384 137.00 ( 0.00%) 131.00 ( 4.38%)
Min free-odr1-1 318.00 ( 0.00%) 289.00 ( 9.12%)
Min free-odr1-2 228.00 ( 0.00%) 207.00 ( 9.21%)
Min free-odr1-4 182.00 ( 0.00%) 165.00 ( 9.34%)
Min free-odr1-8 163.00 ( 0.00%) 146.00 ( 10.43%)
Min free-odr1-16 151.00 ( 0.00%) 135.00 ( 10.60%)
Min free-odr1-32 146.00 ( 0.00%) 129.00 ( 11.64%)
Min free-odr1-64 145.00 ( 0.00%) 130.00 ( 10.34%)
Min free-odr1-128 148.00 ( 0.00%) 134.00 ( 9.46%)
Min free-odr1-256 148.00 ( 0.00%) 137.00 ( 7.43%)
Min free-odr1-512 151.00 ( 0.00%) 140.00 ( 7.28%)
Min free-odr1-1024 154.00 ( 0.00%) 143.00 ( 7.14%)
Min free-odr1-2048 156.00 ( 0.00%) 144.00 ( 7.69%)
Min free-odr1-4096 156.00 ( 0.00%) 142.00 ( 8.97%)
Min free-odr1-8192 156.00 ( 0.00%) 140.00 ( 10.26%)
Min free-odr2-1 361.00 ( 0.00%) 457.00 (-26.59%)
Min free-odr2-2 258.00 ( 0.00%) 224.00 ( 13.18%)
Min free-odr2-4 208.00 ( 0.00%) 223.00 ( -7.21%)
Min free-odr2-8 185.00 ( 0.00%) 160.00 ( 13.51%)
Min free-odr2-16 173.00 ( 0.00%) 149.00 ( 13.87%)
Min free-odr2-32 166.00 ( 0.00%) 145.00 ( 12.65%)
Min free-odr2-64 166.00 ( 0.00%) 146.00 ( 12.05%)
Min free-odr2-128 169.00 ( 0.00%) 148.00 ( 12.43%)
Min free-odr2-256 170.00 ( 0.00%) 152.00 ( 10.59%)
Min free-odr2-512 177.00 ( 0.00%) 156.00 ( 11.86%)
Min free-odr2-1024 182.00 ( 0.00%) 162.00 ( 10.99%)
Min free-odr2-2048 181.00 ( 0.00%) 160.00 ( 11.60%)
Min free-odr2-4096 180.00 ( 0.00%) 159.00 ( 11.67%)
Min free-odr3-1 431.00 ( 0.00%) 367.00 ( 14.85%)
Min free-odr3-2 306.00 ( 0.00%) 259.00 ( 15.36%)
Min free-odr3-4 249.00 ( 0.00%) 208.00 ( 16.47%)
Min free-odr3-8 224.00 ( 0.00%) 186.00 ( 16.96%)
Min free-odr3-16 208.00 ( 0.00%) 176.00 ( 15.38%)
Min free-odr3-32 206.00 ( 0.00%) 174.00 ( 15.53%)
Min free-odr3-64 210.00 ( 0.00%) 178.00 ( 15.24%)
Min free-odr3-128 215.00 ( 0.00%) 182.00 ( 15.35%)
Min free-odr3-256 224.00 ( 0.00%) 189.00 ( 15.62%)
Min free-odr3-512 232.00 ( 0.00%) 195.00 ( 15.95%)
Min free-odr3-1024 230.00 ( 0.00%) 195.00 ( 15.22%)
Min free-odr3-2048 229.00 ( 0.00%) 193.00 ( 15.72%)
Min free-odr4-1 561.00 ( 0.00%) 439.00 ( 21.75%)
Min free-odr4-2 418.00 ( 0.00%) 318.00 ( 23.92%)
Min free-odr4-4 339.00 ( 0.00%) 269.00 ( 20.65%)
Min free-odr4-8 299.00 ( 0.00%) 239.00 ( 20.07%)
Min free-odr4-16 289.00 ( 0.00%) 234.00 ( 19.03%)
Min free-odr4-32 291.00 ( 0.00%) 235.00 ( 19.24%)
Min free-odr4-64 298.00 ( 0.00%) 238.00 ( 20.13%)
Min free-odr4-128 308.00 ( 0.00%) 251.00 ( 18.51%)
Min free-odr4-256 321.00 ( 0.00%) 267.00 ( 16.82%)
Min free-odr4-512 327.00 ( 0.00%) 269.00 ( 17.74%)
Min free-odr4-1024 326.00 ( 0.00%) 271.00 ( 16.87%)
Min total-odr0-1 644.00 ( 0.00%) 494.00 ( 23.29%)
Min total-odr0-2 466.00 ( 0.00%) 356.00 ( 23.61%)
Min total-odr0-4 376.00 ( 0.00%) 291.00 ( 22.61%)
Min total-odr0-8 328.00 ( 0.00%) 251.00 ( 23.48%)
Min total-odr0-16 304.00 ( 0.00%) 234.00 ( 23.03%)
Min total-odr0-32 289.00 ( 0.00%) 224.00 ( 22.49%)
Min total-odr0-64 282.00 ( 0.00%) 218.00 ( 22.70%)
Min total-odr0-128 280.00 ( 0.00%) 216.00 ( 22.86%)
Min total-odr0-256 310.00 ( 0.00%) 243.00 ( 21.61%)
Min total-odr0-512 329.00 ( 0.00%) 273.00 ( 17.02%)
Min total-odr0-1024 346.00 ( 0.00%) 290.00 ( 16.18%)
Min total-odr0-2048 357.00 ( 0.00%) 304.00 ( 14.85%)
Min total-odr0-4096 367.00 ( 0.00%) 315.00 ( 14.17%)
Min total-odr0-8192 372.00 ( 0.00%) 317.00 ( 14.78%)
Min total-odr0-16384 373.00 ( 0.00%) 319.00 ( 14.48%)
Min total-odr1-1 838.00 ( 0.00%) 739.00 ( 11.81%)
Min total-odr1-2 619.00 ( 0.00%) 543.00 ( 12.28%)
Min total-odr1-4 495.00 ( 0.00%) 433.00 ( 12.53%)
Min total-odr1-8 440.00 ( 0.00%) 382.00 ( 13.18%)
Min total-odr1-16 407.00 ( 0.00%) 353.00 ( 13.27%)
Min total-odr1-32 398.00 ( 0.00%) 341.00 ( 14.32%)
Min total-odr1-64 389.00 ( 0.00%) 336.00 ( 13.62%)
Min total-odr1-128 392.00 ( 0.00%) 341.00 ( 13.01%)
Min total-odr1-256 391.00 ( 0.00%) 344.00 ( 12.02%)
Min total-odr1-512 396.00 ( 0.00%) 349.00 ( 11.87%)
Min total-odr1-1024 402.00 ( 0.00%) 357.00 ( 11.19%)
Min total-odr1-2048 409.00 ( 0.00%) 364.00 ( 11.00%)
Min total-odr1-4096 414.00 ( 0.00%) 366.00 ( 11.59%)
Min total-odr1-8192 417.00 ( 0.00%) 369.00 ( 11.51%)
Min total-odr2-1 921.00 ( 0.00%) 1210.00 (-31.38%)
Min total-odr2-2 682.00 ( 0.00%) 576.00 ( 15.54%)
Min total-odr2-4 547.00 ( 0.00%) 616.00 (-12.61%)
Min total-odr2-8 483.00 ( 0.00%) 406.00 ( 15.94%)
Min total-odr2-16 449.00 ( 0.00%) 376.00 ( 16.26%)
Min total-odr2-32 437.00 ( 0.00%) 366.00 ( 16.25%)
Min total-odr2-64 431.00 ( 0.00%) 363.00 ( 15.78%)
Min total-odr2-128 433.00 ( 0.00%) 365.00 ( 15.70%)
Min total-odr2-256 434.00 ( 0.00%) 371.00 ( 14.52%)
Min total-odr2-512 446.00 ( 0.00%) 379.00 ( 15.02%)
Min total-odr2-1024 461.00 ( 0.00%) 392.00 ( 14.97%)
Min total-odr2-2048 464.00 ( 0.00%) 395.00 ( 14.87%)
Min total-odr2-4096 465.00 ( 0.00%) 398.00 ( 14.41%)
Min total-odr3-1 1060.00 ( 0.00%) 872.00 ( 17.74%)
Min total-odr3-2 778.00 ( 0.00%) 633.00 ( 18.64%)
Min total-odr3-4 632.00 ( 0.00%) 510.00 ( 19.30%)
Min total-odr3-8 565.00 ( 0.00%) 452.00 ( 20.00%)
Min total-odr3-16 524.00 ( 0.00%) 424.00 ( 19.08%)
Min total-odr3-32 514.00 ( 0.00%) 415.00 ( 19.26%)
Min total-odr3-64 515.00 ( 0.00%) 419.00 ( 18.64%)
Min total-odr3-128 523.00 ( 0.00%) 426.00 ( 18.55%)
Min total-odr3-256 541.00 ( 0.00%) 438.00 ( 19.04%)
Min total-odr3-512 559.00 ( 0.00%) 451.00 ( 19.32%)
Min total-odr3-1024 561.00 ( 0.00%) 456.00 ( 18.72%)
Min total-odr3-2048 562.00 ( 0.00%) 459.00 ( 18.33%)
Min total-odr4-1 1328.00 ( 0.00%) 1011.00 ( 23.87%)
Min total-odr4-2 997.00 ( 0.00%) 747.00 ( 25.08%)
Min total-odr4-4 813.00 ( 0.00%) 615.00 ( 24.35%)
Min total-odr4-8 721.00 ( 0.00%) 550.00 ( 23.72%)
Min total-odr4-16 689.00 ( 0.00%) 529.00 ( 23.22%)
Min total-odr4-32 683.00 ( 0.00%) 528.00 ( 22.69%)
Min total-odr4-64 692.00 ( 0.00%) 531.00 ( 23.27%)
Min total-odr4-128 713.00 ( 0.00%) 556.00 ( 22.02%)
Min total-odr4-256 738.00 ( 0.00%) 586.00 ( 20.60%)
Min total-odr4-512 753.00 ( 0.00%) 595.00 ( 20.98%)
Min total-odr4-1024 752.00 ( 0.00%) 600.00 ( 20.21%)
This patch (of 27):
order-0 pages by definition cannot be compound so avoid the check in the
fast path for those pages.
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)
diff -puN mm/page_alloc.c~mm-page_alloc-only-check-pagecompound-for-high-order-pages mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_alloc-only-check-pagecompound-for-high-order-pages
+++ a/mm/page_alloc.c
@@ -1024,24 +1024,33 @@ void __meminit reserve_bootmem_region(un
static bool free_pages_prepare(struct page *page, unsigned int order)
{
- bool compound = PageCompound(page);
- int i, bad = 0;
+ int bad = 0;
VM_BUG_ON_PAGE(PageTail(page), page);
- VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
trace_mm_page_free(page, order);
kmemcheck_free_shadow(page, order);
kasan_free_pages(page, order);
+ /*
+ * Check tail pages before head page information is cleared to
+ * avoid checking PageCompound for order-0 pages.
+ */
+ if (order) {
+ bool compound = PageCompound(page);
+ int i;
+
+ VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
+
+ for (i = 1; i < (1 << order); i++) {
+ if (compound)
+ bad += free_tail_pages_check(page, page + i);
+ bad += free_pages_check(page + i);
+ }
+ }
if (PageAnon(page))
page->mapping = NULL;
bad += free_pages_check(page);
- for (i = 1; i < (1 << order); i++) {
- if (compound)
- bad += free_tail_pages_check(page, page + i);
- bad += free_pages_check(page + i);
- }
if (bad)
return false;
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-page_alloc-only-check-pagecompound-for-high-order-pages.patch
mm-page_alloc-use-new-pageanonhead-helper-in-the-free-page-fast-path.patch
mm-page_alloc-reduce-branches-in-zone_statistics.patch
mm-page_alloc-inline-zone_statistics.patch
mm-page_alloc-inline-the-fast-path-of-the-zonelist-iterator.patch
mm-page_alloc-use-__dec_zone_state-for-order-0-page-allocation.patch
mm-page_alloc-avoid-unnecessary-zone-lookups-during-pageblock-operations.patch
mm-page_alloc-convert-alloc_flags-to-unsigned.patch
mm-page_alloc-convert-nr_fair_skipped-to-bool.patch
mm-page_alloc-remove-unnecessary-local-variable-in-get_page_from_freelist.patch
mm-page_alloc-remove-unnecessary-initialisation-in-get_page_from_freelist.patch
mm-page_alloc-remove-redundant-check-for-empty-zonelist.patch
mm-page_alloc-simplify-last-cpupid-reset.patch
mm-page_alloc-move-might_sleep_if-check-to-the-allocator-slowpath.patch
mm-page_alloc-move-__gfp_hardwall-modifications-out-of-the-fastpath.patch
mm-page_alloc-check-once-if-a-zone-has-isolated-pageblocks.patch
mm-page_alloc-shorten-the-page-allocator-fast-path.patch
mm-page_alloc-reduce-cost-of-fair-zone-allocation-policy-retry.patch
mm-page_alloc-shortcut-watermark-checks-for-order-0-pages.patch
mm-page_alloc-avoid-looking-up-the-first-zone-in-a-zonelist-twice.patch
mm-page_alloc-remove-field-from-alloc_context.patch
mm-page_alloc-check-multiple-page-fields-with-a-single-branch.patch
mm-page_alloc-remove-unnecessary-variable-from-free_pcppages_bulk.patch
mm-page_alloc-inline-pageblock-lookup-in-page-free-fast-paths.patch
mm-page_alloc-defer-debugging-checks-of-freed-pages-until-a-pcp-drain.patch
mm-page_alloc-defer-debugging-checks-of-pages-allocated-from-the-pcp.patch
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