From: Dave Hansen <dave.hansen@intel.com>
To: paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org
Cc: 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 10:17:19 -0700 [thread overview]
Message-ID: <53A8611F.1000804@intel.com> (raw)
In-Reply-To: <53A85BF9.7030006@intel.com>
On 06/23/2014 09:55 AM, 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.
>
> I'll go back and compare the grace period ages to see if I can tell what
> is going on.
RCU_TRACE interferes with the benchmark a little bit, and it lowers the
delta that the regression causes. So, evaluate this cautiously.
According to rcu_sched/rcugp, the average "age" is:
v3.16-rc1, with ac1bea85 reverted: 10.7
v3.16-rc1, plus e552592e: 6.1
Paul, have you been keeping an eye on rcugp? Even if I run my system
with only 10 threads, I still see this basic pattern where the average
"age" is lower when I see lower performance. It seems to be a
reasonable proxy that could be used instead of waiting on me to re-run
tests.
next prev parent reply other threads:[~2014-06-23 17:17 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
2014-06-23 17:17 ` Dave Hansen [this message]
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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