From: Waiman Long <waiman.long@hp.com>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Scott J Norton <scott.norton@hp.com>,
Douglas Hatch <doug.hatch@hp.com>
Subject: Re: [PATCH v3 3/7] locking/pvqspinlock: Collect slowpath lock statistics
Date: Mon, 27 Jul 2015 13:33:53 -0400 [thread overview]
Message-ID: <55B66B81.1070508@hp.com> (raw)
In-Reply-To: <1437959674.25997.30.camel@stgolabs.net>
On 07/26/2015 09:14 PM, Davidlohr Bueso wrote:
> On Wed, 2015-07-22 at 16:12 -0400, Waiman Long wrote:
>> This patch enables the accumulation of kicking and waiting related
>> PV qspinlock statistics when the new QUEUED_LOCK_STAT configuration
>> option is selected. It also enables the collection of kicking and
>> wakeup latencies which have a heavy dependency on the CPUs being used.
>>
>> The measured latencies for different CPUs are:
>>
>> CPU Wakeup Kicking
>> --- ------ -------
>> Haswell-EX 89.8us 7.4us
>> Westmere-EX 67.6us 9.3us
>>
> But you don't mention anything about the overhead of enabling
> QUEUED_LOCK_STAT. This does several atomic ops, thus potentially
> thrashing workloads.
>
Yes, QUEUED_LOCK_STAT will slow performance a bit. It is like enabling
LOCK_STAT and you will expect some slow down too. It is essentially a
debugging option to see what had actually happened in the system. It
should be turned off in a production system.
Cheers,
Longman
next prev parent reply other threads:[~2015-07-27 17:33 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-22 20:12 [PATCH v3 0/7] locking/qspinlock: Enhance pvqspinlock performance Waiman Long
2015-07-22 20:12 ` [PATCH v3 1/7] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL Waiman Long
2015-07-25 22:31 ` Davidlohr Bueso
2015-07-27 1:46 ` Davidlohr Bueso
2015-07-27 17:50 ` Waiman Long
2015-07-27 18:41 ` Davidlohr Bueso
2015-07-31 8:39 ` Peter Zijlstra
2015-07-31 17:01 ` Waiman Long
2015-07-22 20:12 ` [PATCH v3 2/7] locking/pvqspinlock: Add pending bit support Waiman Long
2015-07-26 23:09 ` Davidlohr Bueso
2015-07-27 17:11 ` Waiman Long
2015-07-26 23:48 ` Davidlohr Bueso
2015-07-27 0:56 ` Davidlohr Bueso
2015-07-27 17:30 ` Waiman Long
2015-07-27 19:39 ` Davidlohr Bueso
2015-07-29 20:49 ` Waiman Long
2015-07-27 20:08 ` Davidlohr Bueso
2015-07-22 20:12 ` [PATCH v3 3/7] locking/pvqspinlock: Collect slowpath lock statistics Waiman Long
2015-07-27 1:14 ` Davidlohr Bueso
2015-07-27 17:33 ` Waiman Long [this message]
2015-07-22 20:12 ` [PATCH v3 4/7] locking/pvqspinlock: Enable deferment of vCPU kicking to unlock call Waiman Long
2015-07-22 20:12 ` [PATCH v3 5/7] locking/pvqspinlock: Allow vCPUs kick-ahead Waiman Long
2015-07-22 20:12 ` [PATCH v3 6/7] locking/pvqspinlock: Queue node adaptive spinning Waiman Long
2015-07-22 20:12 ` [PATCH v3 7/7] locking/pvqspinlock, x86: Optimize PV unlock code path Waiman Long
2015-07-27 1:18 ` [PATCH v3 0/7] locking/qspinlock: Enhance pvqspinlock performance Davidlohr Bueso
2015-07-27 17:36 ` Waiman Long
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