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| author |   Eric Dumazet <dada1@cosmosbay.com> | 2008-02-06 01:37:56 -0800 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-06 10:41:09 -0800 |
| commit | 1bf47346d75790ebd2563d909d48046961c7ffd5 (patch) | |
| tree | 0f478764beb8dc4e0c71c5f3d6a657535579fe3a /lib/smp_processor_id.c | |
| parent | idle_regs() must be __cpuinit (diff) | |
| download | linux-dev-1bf47346d75790ebd2563d909d48046961c7ffd5.tar.xz linux-dev-1bf47346d75790ebd2563d909d48046961c7ffd5.zip | |
kernel/sys.c: get rid of expensive divides in groups_sort()
groups_sort() can be quite long if user loads a large gid table.
This is because GROUP_AT(group_info, some_integer) uses an integer divide.
So having to do XXX thousand divides during one syscall can lead to very
high latencies. (NGROUPS_MAX=65536)
In the past (25 Mar 2006), an analog problem was found in groups_search()
(commit d74beb9f33a5f16d2965f11b275e401f225c949d ) and at that time I
changed some variables to unsigned int.
I believe that a more generic fix is to make sure NGROUPS_PER_BLOCK is
unsigned.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/smp_processor_id.c')
0 files changed, 0 insertions, 0 deletions