Re: CONFIG_NO_HZ breaks blktrace timestamps

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On Fri, Jan 11 2008, Ingo Molnar wrote:
> 
> * Jens Axboe <jens.axboe@xxxxxxxxxx> wrote:
> 
> > > they are from the scheduler git tree (except the first debug patch), 
> > > but queued up for v2.6.25 at the moment.
> > 
> > So this means that blktrace will be broken with CONFIG_NO_HZ for 
> > 2.6.24? That's clearly a regression.
> 
> 64-bit CONFIG_NO_HZ is a new feature in v2.6.24. If it happens on 32-bit 
> too and it didnt happen in v2.6.23 32-bit then it's a regression.

If blktrace worked in 2.6.23 and it doesn't in 2.6.24 because of some
option that isn't immediately apparent, then it's a regression. Period.

> all this comes from blktrace's original decision of using sched_clock()
> :-) It's not a global timesource and it's not trivial to turn it into a
> halfways usable global timesource.

Hey, it was a high res time source and the only one easily available :)
I'm fine with using another timesource, I'll take suggestions or patches
any day!

-- 
Jens Axboe

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