linux-kernel - Re: [Qemu-devel] [RFC] Next gen kvm api

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Message-ID: <4F31132F.3010100@redhat.com>
Date:	Tue, 07 Feb 2012 14:03:59 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Anthony Liguori <anthony@...emonkey.ws>
CC:	Rob Earhart <earhart@...gle.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>
Subject: Re: [Qemu-devel] [RFC] Next gen kvm api

On 02/06/2012 09:11 PM, Anthony Liguori wrote:
>
> I'm not so sure.  ioeventfds and a future mmio-over-socketpair have to 
> put the kthread to sleep while it waits for the other end to process 
> it.  This is effectively equivalent to a heavy weight exit.  The 
> difference in cost is dropping to userspace which is really neglible 
> these days (< 100 cycles).

On what machine did you measure these wonderful numbers?

But I agree a heavyweight exit is probably faster than a double context 
switch on a remote core.


-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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