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From: Davidlohr Bueso <dave@stgolabs.net>
To: Waiman Long <Waiman.Long@hpe.com>
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 v6 4/6] locking/pvqspinlock: Collect slowpath lock statistics
Date: Fri, 11 Sep 2015 16:13:55 -0700	[thread overview]
Message-ID: <20150911231355.GD19736@linux-q0g1.site> (raw)
In-Reply-To: <1441996658-62854-5-git-send-email-Waiman.Long@hpe.com>

On Fri, 11 Sep 2015, Waiman Long wrote:

>A sample of statistics counts after system bootup (with vCPU
>overcommit) was:
>
>hash_hops_count=9001
>kick_latencies=138047878
>kick_unlock_count=9001
>kick_wait_count=9000
>spurious_wakeup=3
>wait_again_count=2
>wait_head_count=10
>wait_node_count=8994
>wake_latencies=713195944

Any reason you chose not to make the stats per-cpu? The locking
numbers don't have to be exact, so you can easily get away with
it and suffer from much less overhead that resorting to atomics.
Obviously assuming that reading/collecting the stats is done
infrequently, such as between workloads or at bootup as you did.

Thanks,
Davidlohr

  reply	other threads:[~2015-09-11 23:14 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-11 18:37 [PATCH v6 0/6] locking/qspinlock: Enhance pvqspinlock performance Waiman Long
2015-09-11 18:37 ` [PATCH v6 1/6] locking/qspinlock: relaxes cmpxchg & xchg ops in native code Waiman Long
2015-09-11 22:27   ` Davidlohr Bueso
2015-09-14 12:06     ` Peter Zijlstra
2015-09-14 18:40       ` Waiman Long
2015-09-14 15:16     ` Waiman Long
2015-09-11 18:37 ` [PATCH v6 2/6] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL Waiman Long
2015-09-18  8:50   ` [tip:locking/core] locking/pvqspinlock: Kick the PV CPU unconditionally when _Q_SLOW_VAL tip-bot for Waiman Long
2015-09-11 18:37 ` [PATCH v6 3/6] locking/pvqspinlock, x86: Optimize PV unlock code path Waiman Long
2015-09-11 18:37 ` [PATCH v6 4/6] locking/pvqspinlock: Collect slowpath lock statistics Waiman Long
2015-09-11 23:13   ` Davidlohr Bueso [this message]
2015-09-14 15:25     ` Waiman Long
2015-09-14 21:41       ` Davidlohr Bueso
2015-09-15  3:47         ` Waiman Long
2015-09-11 18:37 ` [PATCH v6 5/6] locking/pvqspinlock: Allow 1 lock stealing attempt Waiman Long
2015-09-14 13:57   ` Peter Zijlstra
2015-09-14 19:02     ` Waiman Long
2015-09-14 14:00   ` Peter Zijlstra
2015-09-14 19:15     ` Waiman Long
2015-09-14 19:38       ` Waiman Long
2015-09-15  8:24       ` Peter Zijlstra
2015-09-15 15:29         ` Waiman Long
2015-09-16 15:01           ` Peter Zijlstra
2015-09-17 15:08             ` Waiman Long
2015-09-14 14:04   ` Peter Zijlstra
2015-09-14 19:19     ` Waiman Long
2015-09-11 18:37 ` [PATCH v6 6/6] locking/pvqspinlock: Queue node adaptive spinning Waiman Long
2015-09-14 14:10   ` Peter Zijlstra
2015-09-14 19:37     ` Waiman Long
2015-09-15  8:38       ` Peter Zijlstra
2015-09-15 15:32         ` Waiman Long
2015-09-16 15:03           ` Peter Zijlstra

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