Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760220Ab0FQO4U (ORCPT ); Thu, 17 Jun 2010 10:56:20 -0400 Received: from sprinkles.athenacr.com ([64.95.46.210]:19548 "EHLO sprinkles.inp.in.athenacr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756173Ab0FQO4T (ORCPT ); Thu, 17 Jun 2010 10:56:19 -0400 Message-ID: <4C1A378F.7070604@athenacr.com> Date: Thu, 17 Jun 2010 10:56:15 -0400 From: Brian Bloniarz User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100423 Thunderbird/3.0.4 MIME-Version: 1.0 To: Peter Zijlstra CC: Mike Galbraith , Jiri Kosina , Chris Wedgwood , Linus Torvalds , Greg KH , Alan Cox , OGAWA Hirofumi , Jef Driesen , linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner Subject: Re: Slow pty's (was Re: libdivecomputer interfaces?) References: <20100610181042.GA19210@puku.stupidest.org> <4C116652.8010408@athenacr.com> <1276701411.30669.6.camel@marge.simson.net> <1276756770.8248.20.camel@marge.simson.net> <1276758038.9628.1.camel@marge.simson.net> <1276771844.8121.14.camel@marge.simson.net> <1276781044.27822.309.camel@twins> In-Reply-To: <1276781044.27822.309.camel@twins> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2395 Lines: 73 On 06/17/2010 09:24 AM, Peter Zijlstra wrote: > On Thu, 2010-06-17 at 12:50 +0200, Mike Galbraith wrote: > >> sched: do not ratelimit NOHZ when the tick is stopped. >> >> Chris Wedgwood reports that 39c0cbe sched: Rate-limit nohz causes a serial >> console regression, unresponsiveness, and indeed it does. The below fixes >> it by not skipping out when the tick has been stopped. >> >> Tested that the throughput benefit of ratelimiting is still intact. It is. >> >> Signed-off-by: Mike Galbraith >> Reported-by: Chris Wedgwood > >> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c >> index 5f171f0..83c5129 100644 >> --- a/kernel/time/tick-sched.c >> +++ b/kernel/time/tick-sched.c >> @@ -315,7 +315,7 @@ void tick_nohz_stop_sched_tick(int inidle) >> goto end; >> } >> >> - if (nohz_ratelimit(cpu)) >> + if (!ts->tick_stopped && nohz_ratelimit(cpu)) >> goto end; >> >> ts->idle_calls++; >> > > > Humm,. the code around there suggests something like the below, but I > must admit its been a while since I really read all that nohz stuff, > Thomas, any preferences? I tested Peter's variant, it eliminates the kvm console echo latency that I was seeing. (I haven't tried Mike's earlier variant). Tested-by: Brian Bloniarz > --- > kernel/time/tick-sched.c | 5 +---- > 1 files changed, 1 insertions(+), 4 deletions(-) > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > index 5f171f0..e0707ea 100644 > --- a/kernel/time/tick-sched.c > +++ b/kernel/time/tick-sched.c > @@ -315,9 +315,6 @@ void tick_nohz_stop_sched_tick(int inidle) > goto end; > } > > - if (nohz_ratelimit(cpu)) > - goto end; > - > ts->idle_calls++; > /* Read jiffies and the time when jiffies were updated last */ > do { > @@ -328,7 +325,7 @@ void tick_nohz_stop_sched_tick(int inidle) > } while (read_seqretry(&xtime_lock, seq)); > > if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) || > - arch_needs_cpu(cpu)) { > + arch_needs_cpu(cpu) || nohz_ratelimit(cpu)) { > next_jiffies = last_jiffies + 1; > delta_jiffies = 1; > } else { > -- 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/