Performance & VMmark : Linux Timer Rate : Comments

RE: Linux Timer Rate

kefoster — Fri, 08 Aug 2008 18:26:27 GMT

Is this still a problem on ESX 3.5 UP1? The KB Article you listed only lists up to ESX 2.5 but I know we saw a problem like this in 3.0.2.

RE: Linux Timer Rate

drummonds — Tue, 12 Aug 2008 23:34:12 GMT

Well, I wouldn't say that it's ever a "problem". Operating systems need to be interrupted by their timer hardware. Unless we break the abstraction layer and let the guests access the underlying hardware, those interrupts will have to happen in software. It's an unavoidable fact of any virtualization platform.

Of course, when OSes are designed with specific features for virtualization, they can help the hypervisor to reduce the work. Most paravirt guests do precisely this. But again, that comes from the guest and not the hypervisor.

Despite the age of those articles, interrupt rates and timer virtualization for full virtualization have not changed since ESX 2.5.

RE: Linux Timer Rate

kefoster — Fri, 15 Aug 2008 22:39:40 GMT

Thank you for the information!

RE: Linux Timer Rate

dconvery — Wed, 09 Sep 2009 17:10:52 GMT

Scott -

KB #1420 gives me a message that I am not authorized to view it. Has the number been changed perhaps?

Dave Convery
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RE: Linux Timer Rate

drummonds — Mon, 14 Sep 2009 17:35:50 GMT

It looks like that KB has been deprecated and replaced by 1008284, 1005861, 1006072, 1006113, 1005953, 1006090, 1006086, 1006088, and 1005802. But I need to wade through these to find what I need to update this article.

Scott

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RE: Linux Timer Rate

dconvery — Mon, 14 Sep 2009 17:50:50 GMT

Thanks!

Dave Convery
VMware vExpert 2009
http://www.dailyhypervisor.com
http://twitter.com/dconvery

Careful. We don't want to learn from this.
Bill Watterson, "Calvin and Hobbes"