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SUNRPC: Fix a performance regression in the RPC authentication code

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Fix a regression reported by Max Kellermann whereby kernel profiling
showed that his clients were spending 45% of their time in
rpcauth_lookup_credcache.

It turns out that although his processes had identical uid/gid/groups,
generic_match() was failing to detect this, because the task->group_info
pointers were not shared. This again lead to the creation of a huge number
of identical credentials at the RPC layer.

The regression is fixed by comparing the contents of task->group_info
if the actual pointers are not identical.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Trond Myklebust 2008-11-20 16:06:21 -05:00 committed by Linus Torvalds
parent 0cb39aa0ac
commit 23918b0306
1 changed files with 18 additions and 2 deletions
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20
net/sunrpc/auth_generic.c
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@ -133,13 +133,29 @@ static int
generic_match(struct auth_cred *acred, struct rpc_cred *cred, int flags)
{
struct generic_cred *gcred = container_of(cred, struct generic_cred, gc_base);
int i;
if (gcred->acred.uid != acred->uid ||
gcred->acred.gid != acred->gid ||
gcred->acred.group_info != acred->group_info ||
gcred->acred.machine_cred != acred->machine_cred)
return 0;
goto out_nomatch;
/* Optimisation in the case where pointers are identical... */
if (gcred->acred.group_info == acred->group_info)
goto out_match;
/* Slow path... */
if (gcred->acred.group_info->ngroups != acred->group_info->ngroups)
goto out_nomatch;
for (i = 0; i < gcred->acred.group_info->ngroups; i++) {
if (GROUP_AT(gcred->acred.group_info, i) !=
GROUP_AT(acred->group_info, i))
goto out_nomatch;
}
out_match:
return 1;
out_nomatch:
return 0;
}
void __init rpc_init_generic_auth(void)