From: Trond Myklebust Date: Thu, 20 Nov 2008 21:06:21 +0000 (-0500) Subject: SUNRPC: Fix a performance regression in the RPC authentication code X-Git-Tag: v2.6.28-rc6~4 X-Git-Url: http://www.pilppa.org/gitweb/gitweb.cgi?p=linux-2.6-omap-h63xx.git;a=commitdiff_plain;h=23918b03060f6e572168fdde1798a905679d2e06 SUNRPC: Fix a performance regression in the RPC authentication code 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 Signed-off-by: Linus Torvalds --- diff --git a/net/sunrpc/auth_generic.c b/net/sunrpc/auth_generic.c index 744b79fdcb1..4028502f052 100644 --- a/net/sunrpc/auth_generic.c +++ b/net/sunrpc/auth_generic.c @@ -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)