linux-kernel - Re: + paravirt-vmi-timer-patches.patch added to -mm tree

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Message-ID: <45A00BED.6030802@vmware.com>
Date:	Sat, 06 Jan 2007 12:51:57 -0800
From:	Zachary Amsden <zach@...are.com>
To:	Daniel Walker <dwalker@...sta.com>
CC:	linux-kernel@...r.kernel.org, ak@...e.de, chrisw@...s-sol.org,
	jeremy@...source.com, rusty@...tcorp.com.au
Subject: Re: + paravirt-vmi-timer-patches.patch added to -mm tree

Daniel Walker wrote:
> On Sat, 2007-01-06 at 12:37 -0800, Zachary Amsden wrote:
>
>   
>>> There is already a dynamic tick (NO_HZ) system in the -mm tree .. Given
>>> that this implementation seems unnecessary. Why do you need another
>>> different system to do this?
>>>   
>>>       
>> We don't.  This was written before the dynamic tick code, and now they 
>> need to be merged.  Until then, they can safely coexist.
>>     
>
> So really this can't go upstream till that merge happens. What's
> preventing you from just directly using NO_HZ without changes?
>   

For one thing, the fact that it doesn't account for stolen time.  But 
mostly because going through the regular PIT / APIC timer paths has a 
lot of overhead.  So we need a separate timer device, and weaving this 
in with the local APIC timer dependency for SMP on i386 requires changes 
on top of NO_HZ.

Zach
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