Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030427AbWAXJoU (ORCPT ); Tue, 24 Jan 2006 04:44:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030430AbWAXJoU (ORCPT ); Tue, 24 Jan 2006 04:44:20 -0500 Received: from mustang.oldcity.dca.net ([216.158.38.3]:43142 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S1030427AbWAXJoT (ORCPT ); Tue, 24 Jan 2006 04:44:19 -0500 Subject: Re: RCU latency regression in 2.6.16-rc1 From: Lee Revell To: Ingo Molnar Cc: "Paul E. McKenney" , linux-kernel , Linus Torvalds In-Reply-To: <20060124092330.GA7060@elte.hu> References: <1138089139.2771.78.camel@mindpipe> <20060124075640.GA24806@elte.hu> <1138089483.2771.81.camel@mindpipe> <20060124080157.GA25855@elte.hu> <1138090078.2771.88.camel@mindpipe> <20060124081301.GC25855@elte.hu> <1138090527.2771.91.camel@mindpipe> <20060124091730.GA31204@us.ibm.com> <20060124092330.GA7060@elte.hu> Content-Type: text/plain Date: Tue, 24 Jan 2006 04:44:15 -0500 Message-Id: <1138095856.2771.103.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.5.4 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1836 Lines: 43 On Tue, 2006-01-24 at 10:23 +0100, Ingo Molnar wrote: > * Paul E. McKenney wrote: > > > > Have not tested yet but it appears that will reduce it substantially: > > > > > > $ grep "dst_destroy (dst_rcu_free)" /proc/latency_trace | wc -l > > > 3027 > > > > > > This implies the latency would be reduced to ~4ms, still not great but > > > it will be overshadowed by rt_run_flush/rt_garbage_collect. > > > > The other patch to try would be Dipankar Sarma's patch at: > > > > http://marc.theaimsgroup.com/?l=linux-kernel&m=113657112726596&w=2 > > > > This patch was primarily designed to reduce memory overhead, but given > > that it tends to reduce batch size, it should also reduce latency. > > if this solves Lee's problem, i think we should apply this as a fix, and > get it into v2.6.16. The patch looks straightforward and correct to me. > Does not compile: CC kernel/rcupdate.o kernel/rcupdate.c:76: warning: 'struct rcu_state' declared inside parameter list kernel/rcupdate.c:76: warning: its scope is only this definition or declaration, which is probably not what you want kernel/rcupdate.c: In function 'call_rcu': kernel/rcupdate.c:113: error: 'rcu_state' undeclared (first use in this function) kernel/rcupdate.c:113: error: (Each undeclared identifier is reported only once kernel/rcupdate.c:113: error: for each function it appears in.) kernel/rcupdate.c: In function 'call_rcu_bh': kernel/rcupdate.c:155: error: 'rcu_bh_state' undeclared (first use in this function) make[1]: *** [kernel/rcupdate.o] Error 1 make: *** [kernel] Error 2 Lee - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/