From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759916AbYLQALT (ORCPT ); Tue, 16 Dec 2008 19:11:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759753AbYLQAGR (ORCPT ); Tue, 16 Dec 2008 19:06:17 -0500 Received: from kroah.org ([198.145.64.141]:41380 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1759719AbYLQAGN (ORCPT ); Tue, 16 Dec 2008 19:06:13 -0500 Date: Tue, 16 Dec 2008 16:04:35 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , Willy Tarreau , Rodrigo Rubira Branco , Jake Edge , Eugene Teo , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Trond Myklebust Subject: [patch 18/22] SUNRPC: Fix a performance regression in the RPC authentication code Message-ID: <20081217000435.GS4504@kroah.com> References: <20081216235704.347182084@mini.kroah.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline; filename="sunrpc-fix-a-performance-regression-in-the-rpc-authentication-code.patch" In-Reply-To: <20081217000306.GA4504@kroah.com> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.27-stable review patch. If anyone has any objections, please let us know. ------------------ From: Trond Myklebust commit 23918b03060f6e572168fdde1798a905679d2e06 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/auth_generic.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) --- 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)