From: Suresh Siddha <suresh.b.siddha@intel.com>
To: Mike Galbraith <efault@gmx.de>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@elte.hu>, Paul Turner <pjt@google.com>
Subject: Re: sched: Avoid SMT siblings in select_idle_sibling() if possible
Date: Mon, 27 Feb 2012 14:11:22 -0800 [thread overview]
Message-ID: <1330380683.23436.16.camel@sbsiddha-desk.sc.intel.com> (raw)
In-Reply-To: <1330158655.11655.58.camel@marge.simpson.net>
On Sat, 2012-02-25 at 09:30 +0100, Mike Galbraith wrote:
> My less rotund config shows the L2 penalty decidedly more prominently.
> We used to have avg_overlap as a synchronous wakeup hint, but it was
> broken by preemption and whatnot, got the axe to recover some cycles. A
> reliable and dirt cheap replacement would be a good thing to have.
>
> TCP_RR and tbench are far way away from the overlap breakeven point on
> E5620, whereas with Q6600s shared L2, you can start converting overlap
> into throughput almost immediately.
>
> 2.4 GHz E5620
> Throughput 248.994 MB/sec 1 procs SD_SHARE_PKG_RESOURCES
> Throughput 379.488 MB/sec 1 procs !SD_SHARE_PKG_RESOURCES
>
> 2.4 GHz Q6600
> Throughput 299.049 MB/sec 1 procs SD_SHARE_PKG_RESOURCES
> Throughput 300.018 MB/sec 1 procs !SD_SHARE_PKG_RESOURCES
>
Also it is not always about just the L2 cache being shared/not or
warm/cold etc. It also depends on the core c-states/p-states etc. It
will cost waking up an idle core and the cost will depend on the what
core-c state it is in. And also if we ping-pong between cores often,
cpufreq governor will come and request for a lower core p-state even
though the load was keeping one core or the other in the socket always
busy at any given point of time.
thanks,
suresh
next prev parent reply other threads:[~2012-02-27 22:12 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-15 9:46 sched: Avoid SMT siblings in select_idle_sibling() if possible Peter Zijlstra
2011-11-16 1:14 ` Suresh Siddha
2011-11-16 9:24 ` Mike Galbraith
2011-11-16 18:37 ` Suresh Siddha
2011-11-17 1:59 ` Mike Galbraith
2011-11-17 15:38 ` Mike Galbraith
2011-11-17 15:56 ` Peter Zijlstra
2011-11-17 16:38 ` Mike Galbraith
2011-11-17 17:36 ` Suresh Siddha
2011-11-18 15:14 ` Mike Galbraith
2011-11-18 15:17 ` [patch 1/6] sched: use rt.nr_cpus_allowed to recover select_task_rq() cycles Mike Galbraith
2011-11-18 15:35 ` Peter Zijlstra
2011-11-18 17:34 ` Mike Galbraith
2011-11-22 14:17 ` Mike Galbraith
2011-11-22 14:18 ` [patch 1/7] " Mike Galbraith
2011-12-06 9:50 ` [tip:sched/core] sched: Use " tip-bot for Mike Galbraith
2011-11-22 14:20 ` [patch 2/7] sched: save some hrtick_start_fair cycles Mike Galbraith
2011-12-06 20:20 ` [tip:sched/core] sched: Save " tip-bot for Mike Galbraith
2011-11-22 14:21 ` [patch 3/7] sched: set skip_clock_update in yield_task_fair() Mike Galbraith
2011-11-23 11:53 ` Peter Zijlstra
2011-11-23 12:06 ` Mike Galbraith
2011-11-23 14:48 ` Peter Zijlstra
2011-11-24 3:50 ` Mike Galbraith
2011-11-24 10:12 ` Peter Zijlstra
2011-11-25 6:39 ` Mike Galbraith
2011-12-06 9:51 ` [tip:sched/core] sched: Set " tip-bot for Mike Galbraith
2011-11-22 14:22 ` [patch 4/7] sched: convert rq->avg_idle to rq->avg_event Mike Galbraith
2011-11-23 11:55 ` Peter Zijlstra
2011-11-23 12:09 ` Mike Galbraith
2011-11-23 12:27 ` Peter Zijlstra
2011-11-23 12:57 ` Mike Galbraith
2011-11-23 14:21 ` Mike Galbraith
2011-11-22 14:23 ` [patch 5/7] sched: ratelimit select_idle_sibling()for sync wakeups Mike Galbraith
2011-11-22 14:24 ` [patch 6/7] sched: use rq->avg_event to resurrect nohz ratelimiting Mike Galbraith
2011-11-23 11:57 ` Peter Zijlstra
2011-11-23 12:35 ` Mike Galbraith
2011-11-22 14:26 ` [patch 7/7] sched: only use TTWU_QUEUE when waker/wakee CPUs do not share top level cache Mike Galbraith
2011-11-23 12:08 ` Peter Zijlstra
2011-11-18 15:39 ` [patch 1/6] sched: use rt.nr_cpus_allowed to recover select_task_rq() cycles Hillf Danton
2011-11-18 15:18 ` [patch 2/6] sched: convert rq->avg_idle to rq->avg_event Mike Galbraith
2011-11-18 15:19 ` [patch 3/6] sched: use rq->avg_event to resurrect nohz ratelimiting Mike Galbraith
2011-11-18 15:36 ` Peter Zijlstra
2011-11-18 17:42 ` Mike Galbraith
2011-11-19 0:51 ` Van De Ven, Arjan
2011-11-19 4:15 ` Mike Galbraith
2011-11-18 15:20 ` [patch 4/6] sched: ratelimit select_idle_sibling()for sync wakeups Mike Galbraith
2011-11-18 15:22 ` [patch 5/6] sched: save some hrtick_start_fair cycles Mike Galbraith
2011-11-18 15:23 ` [patch 6/6] sched: set skip_clock_update in yield_task_fair() Mike Galbraith
2012-02-20 14:41 ` sched: Avoid SMT siblings in select_idle_sibling() if possible Peter Zijlstra
2012-02-20 15:03 ` Srivatsa Vaddagiri
2012-02-20 18:25 ` Mike Galbraith
2012-02-21 0:06 ` Srivatsa Vaddagiri
2012-02-21 6:37 ` Mike Galbraith
2012-02-21 8:09 ` Srivatsa Vaddagiri
2012-02-20 18:14 ` Mike Galbraith
2012-02-20 18:15 ` Peter Zijlstra
2012-02-20 19:07 ` Peter Zijlstra
2012-02-21 5:43 ` Mike Galbraith
2012-02-21 8:32 ` Srivatsa Vaddagiri
2012-02-21 9:21 ` Mike Galbraith
2012-02-21 10:37 ` Peter Zijlstra
2012-02-21 14:58 ` Srivatsa Vaddagiri
2012-02-23 10:49 ` Srivatsa Vaddagiri
2012-02-23 11:19 ` Ingo Molnar
2012-02-23 12:18 ` Srivatsa Vaddagiri
2012-02-23 11:20 ` Srivatsa Vaddagiri
2012-02-23 11:26 ` Ingo Molnar
2012-02-23 11:32 ` Srivatsa Vaddagiri
2012-02-23 16:17 ` Ingo Molnar
2012-02-23 11:21 ` Mike Galbraith
2012-02-25 6:54 ` Srivatsa Vaddagiri
2012-02-25 8:30 ` Mike Galbraith
2012-02-27 22:11 ` Suresh Siddha [this message]
2012-02-28 5:05 ` Mike Galbraith
2011-11-17 19:08 ` Suresh Siddha
2011-11-18 15:12 ` Peter Zijlstra
2011-11-18 15:26 ` Mike Galbraith
2011-12-06 9:49 ` [tip:sched/core] sched: Clean up domain traversal in select_idle_sibling() tip-bot for Suresh Siddha
2011-11-18 23:40 ` [tip:sched/core] sched: Avoid SMT siblings in select_idle_sibling() if possible tip-bot for Peter Zijlstra
[not found] <1329764866.2293.376.camhel@twins>
2012-03-05 15:24 ` Srivatsa Vaddagiri
2012-03-06 9:14 ` Ingo Molnar
2012-03-06 10:03 ` Srivatsa Vaddagiri
2012-03-22 15:32 ` Srivatsa Vaddagiri
2012-03-23 6:38 ` Mike Galbraith
2012-03-26 8:29 ` Peter Zijlstra
2012-03-26 8:36 ` Peter Zijlstra
2012-03-26 17:35 ` Srivatsa Vaddagiri
2012-03-26 18:06 ` Peter Zijlstra
2012-03-27 13:56 ` Mike Galbraith
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