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Re: [kvm-devel] [Qemu-devel] [PATCH] [RFC] Fix time drift of rtc clock +

From: Avi Kivity
Subject: Re: [kvm-devel] [Qemu-devel] [PATCH] [RFC] Fix time drift of rtc clock + general support
Date: Mon, 24 Mar 2008 09:47:28 +0200
User-agent: Thunderbird (X11/20080226)

Avi Kivity wrote:
Paul Brook wrote:
a new timer will be fired to try inject it again soon (==0.1msec)

If the guest is missing interrupts, the chances of a 0.1ms interval working are not great. Most likely It's either going trigger immediately, or be delayed significantly and you're going to end up even further behind.

If 0.1 ms is within qemu's timeslice, then qemu should get the wakeup on time (assuming a host with high resolution timers).

If triggering immediately is OK then why not do that all the time?

Triggering immediately doesn't help, the guest likely has interrupts blocked processing the same interrupt.

If triggering immediately is not acceptable then you're still going to loose interrupts.

You're still accounting for them, so if the load decreases eventually it's going to catch up.

btw, the better solution here is to wait until the guest is ready for timer interrupt injection again, but that's not as easy as arming a timer.

Do not meddle in the internals of kernels, for they are subtle and quick to 

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