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| author | Eric Dumazet <dada1@resalehost.networksolutions.com> | 2006-03-25 03:08:00 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-25 08:22:58 -0800 |
| commit | 231bed205879236357171e50bd8965e70797ecdc (patch) | |
| tree | fe3bb52388510eca3fc19548abd26f4009b94db1 | |
| parent | 76c67de460b3d00b7ab8a96bb18f07ca47d65fba (diff) | |
| download | linux-3.10-231bed205879236357171e50bd8965e70797ecdc.tar.gz linux-3.10-231bed205879236357171e50bd8965e70797ecdc.tar.bz2 linux-3.10-231bed205879236357171e50bd8965e70797ecdc.zip | |
[PATCH] No need to protect current->group_info in sys_getgroups(), in_group_p() and in_egroup_p()
While doing some benchmarks of an Apache/PHP SMP server, I noticed high
oprofile numbers in in_group_p() and _atomic_dec_and_lock().
rank percent
1 4.8911 % __link_path_walk
2 4.8503 % __d_lookup
*3 4.2911 % _atomic_dec_and_lock
4 3.9307 % __copy_to_user_ll
5 4.9004 % sysenter_past_esp
*6 3.3248 % in_group_p
It appears that in_group_p() does an uncessary
get_group_info(current->group_info); /* atomic_inc() */
... /* access current->group_info */
put_group_info(current->group_info); /* _atomic_dec_and_lock */
It is not necessary to do this, because the current task holds a reference
on its own group_info, and this reference cannot change during the lookup.
This patch deletes the get_group_info()/put_group_info() pair from
sys_getgroups(), in_group_p() and in_egroup_p() functions.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: Tim Hockin <thockin@hockin.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | kernel/sys.c | 6 |
1 files changed, 0 insertions, 6 deletions
diff --git a/kernel/sys.c b/kernel/sys.c index 421009cedb5..119fb0d9e24 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1421,7 +1421,6 @@ asmlinkage long sys_getgroups(int gidsetsize, gid_t __user *grouplist) return -EINVAL; /* no need to grab task_lock here; it cannot change */ - get_group_info(current->group_info); i = current->group_info->ngroups; if (gidsetsize) { if (i > gidsetsize) { @@ -1434,7 +1433,6 @@ asmlinkage long sys_getgroups(int gidsetsize, gid_t __user *grouplist) } } out: - put_group_info(current->group_info); return i; } @@ -1475,9 +1473,7 @@ int in_group_p(gid_t grp) { int retval = 1; if (grp != current->fsgid) { - get_group_info(current->group_info); retval = groups_search(current->group_info, grp); - put_group_info(current->group_info); } return retval; } @@ -1488,9 +1484,7 @@ int in_egroup_p(gid_t grp) { int retval = 1; if (grp != current->egid) { - get_group_info(current->group_info); retval = groups_search(current->group_info, grp); - put_group_info(current->group_info); } return retval; } |