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From: Ingo Molnar <mingo@elte.hu>
To: Alexander Graf <agraf@suse.de>
Cc: Sasha Levin <levinsasha928@gmail.com>,
	penberg@kernel.org, kvm@vger.kernel.org, asias.hejun@gmail.com,
	gorcunov@gmail.com, prasadjoshi124@gmail.com
Subject: Re: [PATCH] kvm tools: Add MMIO coalescing support
Date: Sat, 4 Jun 2011 13:27:43 +0200	[thread overview]
Message-ID: <20110604112743.GA24146@elte.hu> (raw)
In-Reply-To: <A41FC14A-F48A-4CDB-94A7-F11E3F5B45D0@suse.de>


* Alexander Graf <agraf@suse.de> wrote:

> > So? I only inquired about latencies, asking what impact on 
> > latencies is. Regardless of the circumstances we do not want to 
> > introduce unbound latencies.
> > 
> > If there are no unbound latencies then i'm happy.
> 
> Sure, I'm just saying that the mechanism was invented for 
> unmodified guests :).

Well, but that does not excuse the introduction of unbound latencies. 
(if those latencies are introduced here - i don't know, i'm asking.)

> > Well, since user-space gets the MMIOs only once the guest exits 
> > it's not independent, is it?
> 
> If we don't know when a guest ends an MMIO stream, we can't 
> optimize it. Period. [...]

But that's no excuse. If you cannot optimize them without 
unnacceptable collateral damage then don't optimize it then.

That's why i asked what the damage is - if there's any damage.

Thanks,

	Ingo

  reply	other threads:[~2011-06-04 11:27 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-03 19:51 [PATCH] kvm tools: Add MMIO coalescing support Sasha Levin
2011-06-04  9:38 ` Ingo Molnar
2011-06-04 10:14   ` Sasha Levin
2011-06-04 10:17     ` Ingo Molnar
2011-06-04 10:28       ` Sasha Levin
2011-06-04 10:35         ` Ingo Molnar
2011-06-04 10:39           ` Alexander Graf
2011-06-04 10:47             ` Ingo Molnar
2011-06-04 10:54               ` Alexander Graf
2011-06-04 11:27                 ` Ingo Molnar [this message]
2011-06-04 11:53                   ` Alexander Graf
2011-06-04 14:46                     ` Ingo Molnar
2011-06-04 15:22                       ` Alexander Graf
2011-06-04 16:34                         ` Ingo Molnar
2011-06-04 16:50                           ` Sasha Levin

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