From: Peter Zijlstra <peterz@infradead.org>
To: paulmck@linux.vnet.ibm.com
Cc: "Alex,Shi" <alex.shi@intel.com>,
"Li, Shaohua" <shaohua.li@intel.com>, Ingo Molnar <mingo@elte.hu>,
lkml <linux-kernel@vger.kernel.org>,
"Chen, Tim C" <tim.c.chen@intel.com>,
rostedt@goodmis.org
Subject: Re: rcu: performance regression
Date: Tue, 14 Jun 2011 15:18:42 +0200 [thread overview]
Message-ID: <1308057522.19856.41.camel@twins> (raw)
In-Reply-To: <1308057298.19856.40.camel@twins>
On Tue, 2011-06-14 at 15:14 +0200, Peter Zijlstra wrote:
> On Tue, 2011-06-14 at 06:02 -0700, Paul E. McKenney wrote:
> > > This commit also cause hackbench process mode performance dropping, and
> > > Shaohua's patch do recovered this. But in hackbench testing, the vmstat
> > > show context switch have some reduce. And perf tool show
> > > root_domain->cpupri->prio_to_cpu[]->lock has contention with the commit.
> >
> > Steven, Peter, would any of the recent fixes address this lock contention?
>
> No. People occasionally run into that thing, but given the constraints
> on SCHED_FIFO SMP (run the n highest priority tasks on m cpus; n<=m)
> there isn't really much we can do.
>
> IIRC Chris Mason once proposed a lockless version, but that opened up
> race windows, Steve might know the details better.
Note that even a lockless version will die of cacheline contention.
next prev parent reply other threads:[~2011-06-14 13:19 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-14 5:26 rcu: performance regression Shaohua Li
2011-06-14 8:13 ` Ingo Molnar
2011-06-14 12:56 ` Paul E. McKenney
2011-06-14 8:33 ` Alex,Shi
2011-06-14 11:37 ` Alex,Shi
2011-06-14 13:02 ` Paul E. McKenney
2011-06-14 13:07 ` Shi, Alex
2011-06-14 13:14 ` Peter Zijlstra
2011-06-14 13:18 ` Peter Zijlstra [this message]
2011-06-14 15:01 ` Paul E. McKenney
2011-06-14 15:10 ` Peter Zijlstra
2011-06-14 15:32 ` Paul E. McKenney
2011-06-14 12:43 ` Paul E. McKenney
2011-06-14 16:48 ` Paul E. McKenney
2011-06-14 20:50 ` Paul E. McKenney
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