From: Dave Hansen <dave.hansen@intel.com>
To: paulmck@linux.vnet.ibm.com
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com,
ak@linux.intel.com, cl@gentwo.org, umgwanakikbuti@gmail.com
Subject: Re: [PATCH tip/core/rcu] Reduce overhead of cond_resched() checks for RCU
Date: Mon, 23 Jun 2014 10:34:19 -0700 [thread overview]
Message-ID: <53A8651B.4010607@intel.com> (raw)
In-Reply-To: <20140623171644.GH4603@linux.vnet.ibm.com>
On 06/23/2014 10:16 AM, Paul E. McKenney wrote:
> On Mon, Jun 23, 2014 at 09:55:21AM -0700, Dave Hansen wrote:
>> This still has a regression. Commit 1ed70de (from Paul's git tree),
>> gets a result of 52231880. If I back up two commits to v3.16-rc1 and
>> revert ac1bea85 (the original culprit) the result goes back up to 57308512.
>>
>> So something is still going on here.
>
> And commit 1ed70de is in fact the right one, so...
>
> The rcutree.jiffies_till_sched_qs boot/sysfs parameter controls how
> long RCU waits before asking for quiescent states. The default is
> currently HZ/20. Does increasing this parameter help? Easy for me to
> increase the default if it does.
Making it an insane value:
echo 12 > /sys/module/rcutree/parameters/jiffies_till_sched_qs
average:52248706
echo 9999999 > /sys/module/rcutree/parameters/jiffies_till_sched_qs
average:55712533
gets us back up _closer_ to our original 57M number, but it's still not
quite there.
next prev parent reply other threads:[~2014-06-23 17:34 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-21 2:59 [PATCH tip/core/rcu] Reduce overhead of cond_resched() checks for RCU Paul E. McKenney
2014-06-21 4:29 ` Josh Triplett
2014-06-21 6:06 ` Paul E. McKenney
2014-06-23 13:53 ` Christoph Lameter
2014-06-23 15:26 ` Paul E. McKenney
2014-06-23 6:26 ` Peter Zijlstra
2014-06-23 13:33 ` Paul E. McKenney
2014-06-23 13:51 ` Christoph Lameter
2014-06-23 16:45 ` Paul E. McKenney
2014-06-23 15:49 ` Andi Kleen
2014-06-23 16:43 ` Paul E. McKenney
2014-06-23 17:19 ` Andi Kleen
2014-06-23 17:42 ` Paul E. McKenney
2014-06-23 16:55 ` Dave Hansen
2014-06-23 17:16 ` Paul E. McKenney
2014-06-23 17:34 ` Dave Hansen [this message]
2014-06-23 17:17 ` Dave Hansen
2014-06-23 18:09 ` Paul E. McKenney
2014-06-23 23:30 ` Dave Hansen
2014-06-24 0:15 ` Paul E. McKenney
2014-06-24 0:20 ` Dave Hansen
2014-06-24 0:39 ` Paul E. McKenney
2014-06-24 16:18 ` Dave Hansen
2014-06-24 20:43 ` Dave Hansen
2014-06-24 21:15 ` Paul E. McKenney
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