|
xen-devel
Re: [Xen-devel] Performance overhead of paravirt_ops on nativeidentified
|
To: |
Jan Beulich <JBeulich@xxxxxxxxxx> |
|
Subject: |
Re: [Xen-devel] Performance overhead of paravirt_ops on nativeidentified |
|
From: |
Peter Zijlstra <peterz@xxxxxxxxxxxxx> |
|
Date: |
Thu, 14 May 2009 10:33:59 +0200 |
|
Cc: |
Nick Piggin <npiggin@xxxxxxx>, Xiaohui Xin <xiaohui.xin@xxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Xin Li <xin.li@xxxxxxxxx>, Jun Nakajima <jun.nakajima@xxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx> |
|
Delivery-date: |
Fri, 15 May 2009 06:32:04 -0700 |
|
Envelope-to: |
www-data@xxxxxxxxxxxxxxxxxxx |
|
In-reply-to: |
<4A0BED040200007800000DB0@xxxxxxxxxxxxxxxxxx> |
|
List-help: |
<mailto:xen-devel-request@lists.xensource.com?subject=help> |
|
List-id: |
Xen developer discussion <xen-devel.lists.xensource.com> |
|
List-post: |
<mailto:xen-devel@lists.xensource.com> |
|
List-subscribe: |
<http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe> |
|
List-unsubscribe: |
<http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe> |
|
References: |
<4A0B62F7.5030802@xxxxxxxx> <4A0BED040200007800000DB0@xxxxxxxxxxxxxxxxxx> |
|
Sender: |
xen-devel-bounces@xxxxxxxxxxxxxxxxxxx |
On Thu, 2009-05-14 at 09:05 +0100, Jan Beulich wrote:
> Wouldn't a third solution be to use ticket spinlocks everywhere, i.e.
> eliminate
> the current indirection, and replace it by an indirection for just the
> contention
> case? As I view it, the problem for Xen aren't really the ticket locks by
> themselves, but rather the extra spinning involved, which is of concern only
> if a lock is contended. We're using ticket locks quite happily in our kernels,
> with directed instead of global wakeup from the unlock path. The only open
> issue we currently have is that while for native keeping interrupts disabled
> while spinning may be acceptable (though I'm not sure how -rt folks are
> viewing this), in a pv environment one should really re-enable interrupts
> here due to the potentially much higher latency.
the -rt folks don't nearly have as many spinlocks, and for those we do
like ticket locks, because they are much fairer and give better worst
case contention behaviour.
Also, for the -rt folks, preempt disable is about as bad as irq disable.
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
|
|
|
Home