From: Waiman Long <waiman.long@hp.com>
To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: linux-arch@vger.kernel.org, Rik van Riel <riel@redhat.com>,
Gleb Natapov <gleb@redhat.com>,
kvm@vger.kernel.org,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Peter Zijlstra <peterz@infradead.org>,
Scott J Norton <scott.norton@hp.com>,
x86@kernel.org, Paolo Bonzini <paolo.bonzini@gmail.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Ingo Molnar <mingo@redhat.com>, Chegu Vinod <chegu_vinod@hp.com>,
David Vrabel <david.vrabel@citrix.com>,
"H. Peter Anvin" <hpa@zytor.com>,
xen-devel@lists.xenproject.org,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>,
Aswin Chandramouleeswaran <aswin@hp.com>
Subject: Re: [PATCH v8 00/10] qspinlock: a 4-byte queue spinlock with PV support
Date: Mon, 07 Apr 2014 12:38:13 -0400 [thread overview]
Message-ID: <5342D475.7060503@hp.com> (raw)
In-Reply-To: <5342425A.7040005@linux.vnet.ibm.com>
On 04/07/2014 02:14 AM, Raghavendra K T wrote:
>
>
> I tested the v7,v8 of qspinlock with unfair config on kvm guest.
> I was curious about unfair locks performance in undercommit cases.
> (overcommit case is expected to perform well)
>
> But I am seeing hang in overcommit cases. Gdb showed that many vcpus
> are halted and there was no progress. Suspecting the problem /race with
> halting, I removed the halt() part of kvm_hibernate(). I am yet to
> take a closer look at the code on halt() related changes.
It seems like there may still be race conditions where the current code
is not handling correctly. I will look into that to see where the
problem is. BTW, what test do you use to produce the hang condition?
>
> Patch series with that change gave around 20% improvement for dbench
> 2x and 30% improvement for ebizzy 2x cases. (1x has no significant
> loss/gain).
>
>
What is the baseline for the performance improvement? Is it without the
unfair lock and PV qspinlock?
-Longman
WARNING: multiple messages have this Message-ID (diff)
From: Waiman Long <waiman.long@hp.com>
To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-arch@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
xen-devel@lists.xenproject.org, kvm@vger.kernel.org,
Paolo Bonzini <paolo.bonzini@gmail.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Rik van Riel <riel@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
David Vrabel <david.vrabel@citrix.com>,
Oleg Nesterov <oleg@redhat.com>, Gleb Natapov <gleb@redhat.com>,
Aswin Chandramouleeswaran <aswin@hp.com>,
Scott J Norton <scott.norton@hp.com>,
Chegu Vinod <chegu_vinod@hp.com>
Subject: Re: [PATCH v8 00/10] qspinlock: a 4-byte queue spinlock with PV support
Date: Mon, 07 Apr 2014 12:38:13 -0400 [thread overview]
Message-ID: <5342D475.7060503@hp.com> (raw)
Message-ID: <20140407163813.PO9NxchrrzuowdWD1WYMC-qPFJFYdRufQne8QITgry0@z> (raw)
In-Reply-To: <5342425A.7040005@linux.vnet.ibm.com>
On 04/07/2014 02:14 AM, Raghavendra K T wrote:
>
>
> I tested the v7,v8 of qspinlock with unfair config on kvm guest.
> I was curious about unfair locks performance in undercommit cases.
> (overcommit case is expected to perform well)
>
> But I am seeing hang in overcommit cases. Gdb showed that many vcpus
> are halted and there was no progress. Suspecting the problem /race with
> halting, I removed the halt() part of kvm_hibernate(). I am yet to
> take a closer look at the code on halt() related changes.
It seems like there may still be race conditions where the current code
is not handling correctly. I will look into that to see where the
problem is. BTW, what test do you use to produce the hang condition?
>
> Patch series with that change gave around 20% improvement for dbench
> 2x and 30% improvement for ebizzy 2x cases. (1x has no significant
> loss/gain).
>
>
What is the baseline for the performance improvement? Is it without the
unfair lock and PV qspinlock?
-Longman
next prev parent reply other threads:[~2014-04-07 16:38 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-02 13:27 [PATCH v8 00/10] qspinlock: a 4-byte queue spinlock with PV support Waiman Long
2014-04-02 13:27 ` [PATCH v8 01/10] qspinlock: A generic 4-byte queue spinlock implementation Waiman Long
2014-04-02 13:27 ` Waiman Long
2014-04-04 13:00 ` Peter Zijlstra
2014-04-04 13:00 ` Peter Zijlstra
2014-04-04 14:59 ` Waiman Long
2014-04-04 14:59 ` Waiman Long
2014-04-04 17:53 ` Ingo Molnar
2014-04-04 17:53 ` Ingo Molnar
2014-04-07 14:16 ` Peter Zijlstra
2014-04-07 14:16 ` Peter Zijlstra
2014-04-04 16:57 ` Konrad Rzeszutek Wilk
2014-04-04 16:57 ` Konrad Rzeszutek Wilk
2014-04-04 17:08 ` Waiman Long
2014-04-04 17:08 ` Waiman Long
2014-04-04 17:54 ` Ingo Molnar
2014-04-04 17:54 ` Ingo Molnar
2014-04-07 14:09 ` Peter Zijlstra
2014-04-07 14:09 ` Peter Zijlstra
2014-04-07 16:59 ` Waiman Long
2014-04-07 16:59 ` Waiman Long
2014-04-07 14:12 ` Peter Zijlstra
2014-04-07 14:12 ` Peter Zijlstra
2014-04-07 14:33 ` Konrad Rzeszutek Wilk
2014-04-07 14:33 ` Konrad Rzeszutek Wilk
2014-04-02 13:27 ` [PATCH v8 02/10] qspinlock, x86: Enable x86-64 to use queue spinlock Waiman Long
2014-04-02 13:27 ` Waiman Long
2014-04-02 13:27 ` [PATCH v8 03/10] qspinlock: More optimized code for smaller NR_CPUS Waiman Long
2014-04-02 13:27 ` Waiman Long
2014-04-02 13:27 ` [PATCH v8 04/10] qspinlock: Optimized code path for 2 contending tasks Waiman Long
2014-04-02 13:27 ` [PATCH v8 05/10] pvqspinlock, x86: Allow unfair spinlock in a PV guest Waiman Long
2014-04-02 13:27 ` Waiman Long
2014-04-02 13:27 ` [PATCH v8 06/10] pvqspinlock: Enable lock stealing in queue lock waiters Waiman Long
2014-04-02 13:27 ` [PATCH v8 07/10] pvqspinlock, x86: Rename paravirt_ticketlocks_enabled Waiman Long
2014-04-02 13:27 ` Waiman Long
2014-04-02 13:27 ` [PATCH v8 08/10] pvqspinlock, x86: Add qspinlock para-virtualization support Waiman Long
2014-04-02 13:27 ` Waiman Long
2014-04-02 13:27 ` [PATCH v8 09/10] pvqspinlock, x86: Enable qspinlock PV support for KVM Waiman Long
2014-04-02 13:27 ` [PATCH v8 10/10] pvqspinlock, x86: Enable qspinlock PV support for XEN Waiman Long
2014-04-02 13:27 ` Waiman Long
2014-04-02 14:39 ` Konrad Rzeszutek Wilk
2014-04-02 14:39 ` Konrad Rzeszutek Wilk
2014-04-02 20:38 ` Waiman Long
2014-04-02 20:38 ` Waiman Long
2014-04-02 14:32 ` [PATCH v8 00/10] qspinlock: a 4-byte queue spinlock with PV support Konrad Rzeszutek Wilk
2014-04-02 14:32 ` Konrad Rzeszutek Wilk
2014-04-02 20:35 ` Waiman Long
2014-04-03 2:10 ` Waiman Long
2014-04-03 2:10 ` Waiman Long
2014-04-03 17:23 ` Konrad Rzeszutek Wilk
2014-04-03 17:23 ` Konrad Rzeszutek Wilk
2014-04-04 2:57 ` Waiman Long
2014-04-04 2:57 ` Waiman Long
2014-04-04 16:55 ` Konrad Rzeszutek Wilk
2014-04-04 16:55 ` Konrad Rzeszutek Wilk
2014-04-04 17:13 ` Waiman Long
2014-04-04 17:13 ` Waiman Long
2014-04-04 17:58 ` Konrad Rzeszutek Wilk
2014-04-04 17:58 ` Konrad Rzeszutek Wilk
2014-04-04 18:33 ` Konrad Rzeszutek Wilk
2014-04-04 18:33 ` Konrad Rzeszutek Wilk
2014-04-04 18:14 ` Marcos E. Matsunaga
2014-04-04 15:25 ` Konrad Rzeszutek Wilk
2014-04-04 15:25 ` Konrad Rzeszutek Wilk
2014-04-07 6:14 ` Raghavendra K T
2014-04-07 16:38 ` Waiman Long [this message]
2014-04-07 16:38 ` Waiman Long
2014-04-07 17:51 ` Raghavendra K T
2014-04-07 17:51 ` Raghavendra K T
2014-04-08 19:15 ` Waiman Long
2014-04-08 19:15 ` Waiman Long
2014-04-09 12:08 ` Raghavendra K T
-- strict thread matches above, loose matches on Subject: below --
2014-04-01 20:47 Waiman Long
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