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From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Lieven <pl@dlhnet.de>
Cc: Vadim Rozenfeld <vrozenfe@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	kvm@vger.kernel.org, gleb@redhat.com, pl@dlh.net
Subject: Re: [RFC PATCH v2 1/2] add support for Hyper-V reference time counter
Date: Thu, 23 May 2013 15:40:23 +0200	[thread overview]
Message-ID: <519E1C47.3070700@redhat.com> (raw)
In-Reply-To: <519E1A09.5080601@dlhnet.de>

Il 23/05/2013 15:30, Peter Lieven ha scritto:
>>>> So I would prefer to remove kvm->arch.hv_ref_count altogether.
>>>
>>> But only if the migration support is guaranteed.
>>
>> Migration support wouldn't work yet anyway, you need to recompute the
>> scale and sequence.  But that could be done by KVM_SET_CLOCK.
> 
> hv_ref_counter does work out of the box. what I was trying to say is
> even it is slower than iTSC, it is significantly faster than hpet
> or pmtimer and I can confirm it works flawlessly with migration.

I can't see how without a userspace patch to migrate hv_ref_count.

>>> And what if we have a host which lacks invariant TSC support?
>>
>> Then the sequence must be set to 0 or 0xFFFFFFFF, I still haven't
>> understood. :)
> 
> yes, but windows does then fall back to pmtimer or hpet which is much
> slower then reference counter.

IIUC, with 0 it doesn't.

Paolo


  reply	other threads:[~2013-05-23 13:40 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-05-19  7:06 [RFC PATCH v2 0/2] Hyper-V timers Vadim Rozenfeld
2013-05-19  7:06 ` [RFC PATCH v2 1/2] add support for Hyper-V reference time counter Vadim Rozenfeld
2013-05-19 13:47   ` Gleb Natapov
2013-05-19 14:37   ` Paolo Bonzini
2013-05-22  0:46   ` Marcelo Tosatti
2013-05-22  3:28     ` Gleb Natapov
2013-05-22  3:32       ` Marcelo Tosatti
2013-05-22  3:38         ` Gleb Natapov
2013-05-22 14:31           ` Marcelo Tosatti
2013-05-22  7:32     ` Vadim Rozenfeld
2013-05-22 21:55       ` Paolo Bonzini
2013-05-23  6:17         ` Peter Lieven
2013-05-23  9:54           ` Paolo Bonzini
2013-05-23 10:45             ` Peter Lieven
2013-05-23 12:25           ` Vadim Rozenfeld
2013-05-23 13:18             ` Paolo Bonzini
2013-05-23 13:20               ` Peter Lieven
2013-05-23 13:23                 ` Paolo Bonzini
2013-05-23 13:30                   ` Peter Lieven
2013-05-23 13:40                     ` Paolo Bonzini [this message]
2013-05-19  7:06 ` [RFC PATCH v2 2/2] add support for Hyper-V invariant TSC Vadim Rozenfeld
2013-05-22  0:50   ` Marcelo Tosatti
2013-05-22  7:22     ` Vadim Rozenfeld
2013-05-22 21:23       ` Marcelo Tosatti
2013-05-23  6:18         ` Peter Lieven
2013-05-23  9:13           ` Gleb Natapov
2013-05-23 13:35             ` Marcelo Tosatti
2013-05-23 15:14               ` Gleb Natapov
2013-05-24  9:57               ` Vadim Rozenfeld
2013-05-23 12:33           ` Vadim Rozenfeld
2013-05-23 12:44             ` Peter Lieven
2013-05-23 12:45               ` Gleb Natapov
2013-05-23 12:54               ` Vadim Rozenfeld
2013-05-23  9:12         ` Gleb Natapov
2013-05-23 13:53           ` Marcelo Tosatti
2013-05-23 15:31             ` Gleb Natapov
2013-05-24 10:11               ` Vadim Rozenfeld
2013-05-24 19:41                 ` Marcelo Tosatti
2013-05-27 12:33                   ` Vadim Rozenfeld
2013-05-23 12:21         ` Vadim Rozenfeld
2013-05-23 13:47           ` Marcelo Tosatti
2013-05-24 10:01             ` Vadim Rozenfeld
2013-05-23 16:44   ` Paolo Bonzini
2013-05-24 10:16     ` Vadim Rozenfeld

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