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Date: Tue, 16 Nov 2010 10:39:24 -0800
From: Jeremy Fitzhardinge <jeremy@goop.org>
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Subject: Re: [RFC][PATCH v2 4/7] taskstats: Add per task steal time accounting
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To: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Michael Holzheu <holzheu@linux.vnet.ibm.com>, Shailabh Nagar <nagar1234@in.ibm.com>, Andrew Morton <akpm@linux-foundation.org>, Venkatesh Pallipadi <venki@google.com>, Suresh Siddha <suresh.b.siddha@intel.com>, Ingo Molnar <mingo@elte.hu>, Oleg Nesterov <oleg@redhat.com>, John stultz <johnstul@us.ibm.com>, Thomas Gleixner <tglx@linutronix.de>, Balbir Singh <balbir@linux.vnet.ibm.com>, Heiko Carstens <heiko.carstens@de.ibm.com>, Roland McGrath <roland@redhat.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>, Avi Kivity <avi@redhat.com>
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On 11/16/2010 08:05 AM, Martin Schwidefsky wrote:
>>> Yes and no. The tracepoint idea looks interesting in itself. But that does
>>> not completely replace the per-task steal time. The hypervisor can take
>>> away the cpu anytime, it is still interesting to know which task was hit
>>> hardest by that. You could view the cpu time lost by a hypercall as
>>> "synchronous" steal time for the task, the remaining delta to the total
>>> per-task steal time as "asynchronous" steal time. 
>> Right, so there is no way the guest knows about the vcpu getting
>> scheduled, it can only derive the fact from hardware clocks after the
>> fact?
> Correct.

Yes, same for Xen.

    J