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| author | Wei Yang <richard.weiyang@gmail.com> | 2017-09-06 16:24:09 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-09-06 17:27:29 -0700 |
| commit | c568da282bbc8f09c4b49201177fa259fe184c47 (patch) | |
| tree | 5d64a076386bd15715c4c287edcd079a17640650 /mm/vmalloc.c | |
| parent | 88d6ac40c1c6b2334046d3f89f1911a3c8febd4c (diff) | |
| download | linux-0-day-c568da282bbc8f09c4b49201177fa259fe184c47.tar.gz linux-0-day-c568da282bbc8f09c4b49201177fa259fe184c47.tar.xz | |
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@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmalloc.c')
| -rw-r--r-- | mm/vmalloc.c | 10 |
1 files changed, 3 insertions, 7 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index a47e3894c7756..fa409c9092be0 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2482,7 +2482,7 @@ static unsigned long pvm_determine_end(struct vmap_area **pnext, * 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, @@ -2510,15 +2510,11 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, 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]; |