From: Peter Zijlstra <peterz@infradead.org>
To: "Ma, Chinang" <chinang.ma@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
Mike Galbraith <efault@gmx.de>,
Gregory Haskins <ghaskins@novell.com>,
Steven Rostedt <rostedt@goodmis.org>,
Nick Piggin <nickpiggin@yahoo.com.au>,
"Siddha, Suresh B" <suresh.b.siddha@intel.com>,
"Wilcox, Matthew R" <matthew.r.wilcox@intel.com>,
"Tripathi, Sharad C" <sharad.c.tripathi@intel.com>,
"Chilukuri, Harita" <harita.chilukuri@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: 2.6.27-rc5 OLTP performance regression
Date: Mon, 08 Sep 2008 20:04:12 +0200 [thread overview]
Message-ID: <1220897052.18239.147.camel@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1220896833.18239.141.camel@twins.programming.kicks-ass.net>
On Mon, 2008-09-08 at 20:00 +0200, Peter Zijlstra wrote:
> On Mon, 2008-09-08 at 10:58 -0700, Ma, Chinang wrote:
> > We found the group scheduler in 2.6.27-rc5 has negative performance
> > impact on TPC Online Transaction Processing workload. The test was
> > conducted on a dual-socket quad-core Xeon server. OLTP workload is
> > disk i/o intensive and we have over 200 database shadow processes
> > running in the server during this test. Enabling group scheduler
> > (CONFIG_GROUP_SCHED=y) reduced performance by 2.0%. Oprofile data
> > indicates significant amount of cycles are spent in tg_shares_up().
> > This is new regression as we did not find the same issue with 2.6.26
> > kernel group scheduler. Is anybody looking into group scheduler
> > performance and any idea for reducing the performance impact?
>
> Because the .26 group scheduler wasn't SMP aware. The extra cost comes
> from the fact that .27 is.
What you can do it increase the /proc/sys/kernel/sched_shares_ratelimit
value and thereby decrease the accuracy of the SMP fairness of the group
scheduler.
next prev parent reply other threads:[~2008-09-08 18:04 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <BC02C49EEB98354DBA7F5DD76F2A9E8002FE60F751@azsmsx501.amr.corp.intel.com>
2008-09-08 18:00 ` Peter Zijlstra
2008-09-08 18:04 ` Peter Zijlstra [this message]
2008-09-09 21:39 ` Ma, Chinang
2008-09-10 12:26 ` Ingo Molnar
2008-09-10 16:14 ` Ma, Chinang
2008-09-10 17:34 ` Ingo Molnar
2008-09-11 0:07 ` Ma, Chinang
2008-09-25 21:04 ` Ma, Chinang
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