From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
To: Waiman Long <Waiman.Long@hp.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>,
Davidlohr Bueso <dave@stgolabs.net>
Subject: Re: [PATCH v2 5/6] locking/pvqspinlock: Opportunistically defer kicking to unlock time
Date: Wed, 15 Jul 2015 11:44:06 +0530 [thread overview]
Message-ID: <55A5FA2E.1040406@linux.vnet.ibm.com> (raw)
In-Reply-To: <1436926417-20256-6-git-send-email-Waiman.Long@hp.com>
On 07/15/2015 07:43 AM, Waiman Long wrote:
> Performing CPU kicking at lock time can be a bit faster if there
> is no kick-ahead. On the other hand, deferring it to unlock time is
> preferrable when kick-ahead can be performed or when the VM guest is
> having too few vCPUs that a vCPU may be kicked twice before getting
> the lock. This patch implements the deferring kicking when either
> one of the above 2 conditions is true.
>
> Linux kernel builds were run in KVM guest on an 8-socket, 4
> cores/socket Westmere-EX system and a 4-socket, 8 cores/socket
> Haswell-EX system. Both systems are configured to have 32 physical
> CPUs. The kernel build times before and after the patch were:
>
> Westmere Haswell
> Patch 32 vCPUs 48 vCPUs 32 vCPUs 48 vCPUs
> ----- -------- -------- -------- --------
> Before patch 3m27.4s 10m32.0s 2m00.8s 14m52.5s
> After patch 3m01.3s 9m50.9s 2m00.5s 13m28.1s
>
> On Westmere, both 32/48 vCPUs case showed some sizeable increase
> in performance. For Haswell, there was some improvement in the
> overcommitted (48 vCPUs) case.
>
> Signed-off-by: Waiman Long <Waiman.Long@hp.com>
> ---
Hi Waiman,
For virtual guests, from my experiments, lock waiter preemption was the
main concern especially with fair locks.
I find that these set of patches are in right direction to address them.
Thanks for the patches.
next prev parent reply other threads:[~2015-07-15 6:14 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-15 2:13 [PATCH 0/6 v2] locking/qspinlock: Enhance pvqspinlock performance Waiman Long
2015-07-15 2:13 ` [PATCH v2 1/6] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL Waiman Long
2015-07-15 9:10 ` Peter Zijlstra
2015-07-16 0:18 ` Waiman Long
2015-07-16 5:42 ` Peter Zijlstra
2015-07-16 14:07 ` Waiman Long
2015-07-16 15:04 ` Waiman Long
2015-07-16 15:10 ` Will Deacon
2015-08-03 16:59 ` [tip:locking/core] locking/Documentation: Clarify failed cmpxchg( ) memory ordering semantics tip-bot for Will Deacon
2015-08-03 17:36 ` Davidlohr Bueso
2015-07-15 2:13 ` [PATCH v2 2/6] locking/pvqspinlock: Add pending bit support Waiman Long
2015-07-15 2:13 ` [PATCH v2 3/6] locking/pvqspinlock: Collect slowpath lock statistics Waiman Long
2015-07-15 2:13 ` [PATCH v2 4/6] locking/pvqspinlock: Allow vCPUs kick-ahead Waiman Long
2015-07-15 9:39 ` Peter Zijlstra
2015-07-16 2:01 ` Waiman Long
2015-07-16 5:46 ` Peter Zijlstra
2015-07-16 14:51 ` Waiman Long
2015-07-15 2:13 ` [PATCH v2 5/6] locking/pvqspinlock: Opportunistically defer kicking to unlock time Waiman Long
2015-07-15 6:14 ` Raghavendra K T [this message]
2015-07-15 10:03 ` Peter Zijlstra
2015-07-16 2:18 ` Waiman Long
2015-07-16 5:49 ` Peter Zijlstra
2015-07-15 2:13 ` [PATCH v2 6/6] locking/pvqspinlock: Queue node adaptive spinning Waiman Long
2015-07-15 10:01 ` Peter Zijlstra
2015-07-16 2:13 ` Waiman Long
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