[Beowulf] Bernhard Kuhn's real time interrupt patch
atp at piskorski.com
Fri Mar 25 18:52:38 EST 2005
On Fri, Mar 25, 2005 at 04:10:15PM -0500, Patrick Geoffray wrote:
> I don't think this patch improves the interrupt latency or the interrupt
> overhead when there is no contention. Context switching is the metric
> you want to improve.
> With OS-bypass NICs, interrupts are rare and there is usually no contention.
Contention for what, the NIC?
I was thinking that Kuhn looked at interrupt latency under heavy CPU
usage, but I guess I was confused. What he actually measured was
greatly tightening up the distribtuion of interrupt latency under
varying network (ping), disk (looping on 'find /'), and "graphics"
(glxgears) loads. I don't understand the ramifications of that.
So is it true that kernel interrupt latency only matters for
non-OS-bypass NICs? (E.g., your typical ethernet card.) And stuff
like Myrinet and SCI doesn't care?
Andrew Piskorski <atp at piskorski.com>
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