Re: [PATCH] Configure IDE probe delays

Alan Cox
2004-09-01T19:49:39Z

On Mer, 2004-09-01 at 20:36, Lee Revell wrote:
> The effect can be measured using a recent version of the voluntary
> preemption patches, and disabling hardirq preemption. In this situation
> the IDE I/O completion is by far the longest non-preemptible code path,
> so can be easily profiled from the latency traces.

A lot of IDE controllers hold off the CPU for long times when you do I/O
cycles. The other factor is PIO which defaults to IRQ masking for safety
on old controllers. For PCI we should probably default the other way.