Re: Preempt? (was Re: Cannot enable DMA on SATA drive (SCSI-libsata, VIA SATA))

[Andrea Arcangeli]

On Tue, Oct 05, 2004 at 11:27:06PM -0400, Jeff Garzik wrote:
> You're ignoring the argument :)
> 
> If users and developers are presented with the _impression_ that long 
> latency code paths don't exist, then nobody is motivated to profile them 
> (with any tool), much less fix them.

well, you are assuming those latencies are visible with eyes. they might
be in extreme cases, but normally they're not (what people notices
normally are disk latencies, and few people uses an RT userspace
anyways which means they cannot claim the problem to be a lack of
cond_resched, but more likely they want shorter timeslices in the
scheduler etc..). So my point is that you need a measurement tool anyways...
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