The patch titled
Subject: mm/vmalloc.c: halve the number of comparisons performed in pcpu_get_vm_areas()
has been added to the -mm tree. Its filename is
mm-vmalloc-reduce-half-comparison-during-pcpu_get_vm_areas.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-vmalloc-reduce-half-comparison-during-pcpu_get_vm_areas.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-vmalloc-reduce-half-comparison-during-pcpu_get_vm_areas.patch
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------------------------------------------------------
From: Wei Yang <richard.weiyang@xxxxxxxxx>
Subject: mm/vmalloc.c: halve the number of comparisons performed in pcpu_get_vm_areas()
In pcpu_get_vm_areas(), it checks each range is not overlapped. To make
sure it is, only (N^2)/2 comparison is necessary, while current code does
N^2 times. By starting from the next range, it achieves the goal and the
continue could be removed.
Also,
- the overlap check of two ranges could be done with one clause
- one typo in comment is fixed.
Link: http://lkml.kernel.org/r/20170803063822.48702-1-richard.weiyang@xxxxxxxxx
Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmalloc.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff -puN mm/vmalloc.c~mm-vmalloc-reduce-half-comparison-during-pcpu_get_vm_areas mm/vmalloc.c
--- a/mm/vmalloc.c~mm-vmalloc-reduce-half-comparison-during-pcpu_get_vm_areas
+++ a/mm/vmalloc.c
@@ -2479,7 +2479,7 @@ static unsigned long pvm_determine_end(s
* matching slot. While scanning, if any of the areas overlaps with
* existing vmap_area, the base address is pulled down to fit the
* area. Scanning is repeated till all the areas fit and then all
- * necessary data structres are inserted and the result is returned.
+ * necessary data structures are inserted and the result is returned.
*/
struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
const size_t *sizes, int nr_vms,
@@ -2507,15 +2507,11 @@ struct vm_struct **pcpu_get_vm_areas(con
if (start > offsets[last_area])
last_area = area;
- for (area2 = 0; area2 < nr_vms; area2++) {
+ for (area2 = area + 1; area2 < nr_vms; area2++) {
unsigned long start2 = offsets[area2];
unsigned long end2 = start2 + sizes[area2];
- if (area2 == area)
- continue;
-
- BUG_ON(start2 >= start && start2 < end);
- BUG_ON(end2 <= end && end2 > start);
+ BUG_ON(start2 < end && start < end2);
}
}
last_end = offsets[last_area] + sizes[last_area];
_
Patches currently in -mm which might be from richard.weiyang@xxxxxxxxx are
mm-memory_hotplug-just-build-zonelist-for-new-added-node.patch
mm-vmalloc-reduce-half-comparison-during-pcpu_get_vm_areas.patch
mm-page_alloc-return-0-in-case-this-node-has-no-page-within-the-zone.patch
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