From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH -rt] timer: upper bound on loops of __run_timers processing Date: Mon, 26 Jan 2015 19:12:31 -0200 Message-ID: <20150126211231.GA32649@amt.cnet> References: <20141230195228.GA3057@amt.cnet> <20150114172147.GA16570@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Clark Williams , Luiz Capitulino , Rik van Riel , linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org To: Thomas Gleixner , Steven Rostedt Return-path: Content-Disposition: inline In-Reply-To: <20150114172147.GA16570@amt.cnet> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org Ping ? On Wed, Jan 14, 2015 at 03:21:47PM -0200, Marcelo Tosatti wrote: > > Ping? > > On Tue, Dec 30, 2014 at 05:52:28PM -0200, Marcelo Tosatti wrote: > > > > Commit "timers: do not raise softirq unconditionally", allows for timer > > wheel processing (__run_timers) to be delayed for long periods of time. > > > > The effect is that > > > > loops = jiffies - base->timer_jiffies > > > > Can grow to very large values resulting in __run_timers taking hundreds > > of milliseconds to execute. > > > > Fix by creating an upper bound on the number of loops to be processed. > > This allows a nohz=off kernel to achieve desired latencies. > > > > Signed-off-by: Marcelo Tosatti > > > > diff --git a/kernel/timer.c b/kernel/timer.c > > index f59e18c..c128416 100644 > > --- a/kernel/timer.c > > +++ b/kernel/timer.c > > @@ -1488,6 +1488,12 @@ void run_local_timers(void) > > } > > #endif > > > > + if (time_after_eq(jiffies, base->timer_jiffies)) { > > + unsigned long jiffies_delta = jiffies - base->timer_jiffies; > > + if (jiffies_delta > TVR_SIZE) > > + raise_softirq(TIMER_SOFTIRQ); > > + } > > + > > if (!base->active_timers) > > goto out; > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html