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authorEric Dumazet <dada1@resalehost.networksolutions.com>2006-03-25 03:08:00 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-25 08:22:58 -0800
commit231bed205879236357171e50bd8965e70797ecdc (patch)
treefe3bb52388510eca3fc19548abd26f4009b94db1 /kernel
parent76c67de460b3d00b7ab8a96bb18f07ca47d65fba (diff)
downloadlinux-sh-231bed205879236357171e50bd8965e70797ecdc.tar.gz
[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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sys.c6
1 files changed, 0 insertions, 6 deletions
diff --git a/kernel/sys.c b/kernel/sys.c
index 421009cedb51..119fb0d9e24e 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;
}