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.

[akpm@linux-foundation.org: use unlikely(order) in free_pages_prepare(), per Vlastimil]
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 8 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6d1c8b06b458..087ba3e417ec 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1024,24 +1024,33 @@ void __meminit reserve_bootmem_region(unsigned long start, unsigned long end)
 
 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 (unlikely(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;