From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964837AbWAZTSh (ORCPT ); Thu, 26 Jan 2006 14:18:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964840AbWAZTSh (ORCPT ); Thu, 26 Jan 2006 14:18:37 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:17309 "EHLO e35.co.us.ibm.com") by vger.kernel.org with ESMTP id S964837AbWAZTSg (ORCPT ); Thu, 26 Jan 2006 14:18:36 -0500 Date: Thu, 26 Jan 2006 11:18:09 -0800 From: "Paul E. McKenney" To: Lee Revell Cc: dipankar@in.ibm.com, Ingo Molnar , linux-kernel , Linus Torvalds Subject: Re: RCU latency regression in 2.6.16-rc1 Message-ID: <20060126191809.GC6182@us.ibm.com> Reply-To: paulmck@us.ibm.com References: <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> <1138095856.2771.103.camel@mindpipe> <20060124162846.GA7139@in.ibm.com> <20060124213802.GC7139@in.ibm.com> <1138224506.3087.22.camel@mindpipe> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1138224506.3087.22.camel@mindpipe> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 25, 2006 at 04:28:25PM -0500, Lee Revell wrote: > On Wed, 2006-01-25 at 03:08 +0530, Dipankar Sarma wrote: > > On Tue, Jan 24, 2006 at 09:58:46PM +0530, Dipankar Sarma wrote: > > > On Tue, Jan 24, 2006 at 04:44:15AM -0500, Lee Revell wrote: > > > > On Tue, 2006-01-24 at 10:23 +0100, Ingo Molnar wrote: > > > > > * Paul E. McKenney wrote: > > > > > > > > > > > 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 > > > > > > My original patch was against a much older kernel. > > > I will send out a more uptodate patch as soon as I am done with some > > > testing. > > > > Here is an updated version of that patch against 2.6.16-rc1. I have > > sanity-tested it on ppc64 and x86_64 using dbench and kernbench. > > I have also tested this for OOM situations - open()/close() in > > a tight loop in my x86_64 which earlier used to reach file limit > > if I set batch limit to 10 and found no problem. This patch does set > > default RCU batch limit to 10 and changes it only when there is an RCU > > flood. > > OK this seems to work, I can't tell yet whether it help the latency I > reported, but rt_run_flush still produces terrible latencies. > > Ingo, should I try the softirq preemption patch + Dipankar's patch + > latency tracing patch? > > preemption latency trace v1.1.5 on 2.6.16-rc1 > -------------------------------------------------------------------- > latency: 7418 us, #6397/6397, CPU#0 | (M:rt VP:0, KP:0, SP:0 HP:0) > ----------------- > | task: gmplayer-8638 (uid:1000 nice:-20 policy:0 rt_prio:0) > ----------------- > > _------=> CPU# > / _-----=> irqs-off > | / _----=> need-resched > || / _---=> hardirq/softirq > ||| / _--=> preempt-depth > |||| / > ||||| delay > cmd pid ||||| time | caller > \ / ||||| \ | / > Xorg-2154 0d.s2 1us : __trace_start_sched_wakeup (try_to_wake_up) > Xorg-2154 0d.s2 2us : __trace_start_sched_wakeup <<...>-8638> (64 0) > Xorg-2154 0d.s. 3us+: wake_up_process (hrtimer_run_queues) > Xorg-2154 0d.s. 6us : rt_secret_rebuild (run_timer_softirq) > Xorg-2154 0d.s. 7us : rt_cache_flush (rt_secret_rebuild) > Xorg-2154 0d.s1 7us : del_timer (rt_cache_flush) > Xorg-2154 0d.s. 9us : local_bh_enable (rt_cache_flush) > Xorg-2154 0d.s. 10us : rt_run_flush (rt_cache_flush) > Xorg-2154 0d.s. 11us : get_random_bytes (rt_run_flush) > Xorg-2154 0d.s. 12us : extract_entropy (get_random_bytes) > Xorg-2154 0d.s. 13us : xfer_secondary_pool (extract_entropy) > Xorg-2154 0d.s. 15us : extract_entropy (xfer_secondary_pool) > Xorg-2154 0d.s. 16us : xfer_secondary_pool (extract_entropy) > Xorg-2154 0d.s. 17us+: account (extract_entropy) > Xorg-2154 0d.s. 19us : extract_buf (extract_entropy) > Xorg-2154 0d.s. 20us : sha_init (extract_buf) > Xorg-2154 0d.s. 21us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 29us+: __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 32us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 39us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 40us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 47us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 48us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 55us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 56us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 63us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 64us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 71us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 73us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 79us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 81us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 87us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 81us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 87us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 89us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 91us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 98us : __add_entropy_words (xfer_secondary_pool) > Xorg-2154 0d.s. 100us : credit_entropy_store (xfer_secondary_pool) > Xorg-2154 0d.s. 101us : account (extract_entropy) > Xorg-2154 0d.s1 102us : __wake_up (account) > Xorg-2154 0d.s2 103us : __wake_up_common (__wake_up) > Xorg-2154 0d.s. 104us : extract_buf (extract_entropy) > Xorg-2154 0d.s. 105us : sha_init (extract_buf) > Xorg-2154 0d.s. 106us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 113us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 114us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 121us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 122us : __add_entropy_words (extract_buf) > Xorg-2154 0d.s. 124us+: sha_transform (extract_buf) > Xorg-2154 0d.s. 132us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 133us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 134us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 135us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 136us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 137us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 139us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 140us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 141us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 142us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 143us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 145us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 146us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 148us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 149us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 150us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 151us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 152us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 154us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 155us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 156us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 157us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 158us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 159us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 161us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 162us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 163us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 164us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 166us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 167us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 168us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 169us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 170us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 172us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 173us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 174us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 175us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 176us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 178us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 179us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 180us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 181us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 182us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 184us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 185us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 186us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 187us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 188us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 190us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 191us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 192us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 193us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 194us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 195us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 197us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 198us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 199us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 200us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 201us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 202us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 204us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 205us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 206us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 207us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 208us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 210us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 211us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 212us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 213us : call_rcu_bh (rt_run_flush) > Xorg-2154 0d.s. 215us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 216us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 217us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 218us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 219us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 220us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 222us : local_bh_enable (rt_run_flush) > Xorg-2154 0d.s. 223us : call_rcu_bh (rt_run_flush) > > [ zillions of these deleted ] > > Xorg-2154 0d.s. 7335us : local_bh_enable (rt_run_flush) Dipankar's latest patch should hopefully address this problem. Could you please give it a spin when you get a chance? Thanx, Paul