Re: low-latency benchmarks: excellent results of RTC clock + SIGIO

Zack Brown (mingo@chiara.csoma.elte.hu)
Sat, 11 Sep 1999 17:46:01 +0200 (CEST)


On Sat, 11 Sep 1999, Benno Senoner wrote:

> Seems that under high disk I/O load,
> (very seldom, about every 30-100secs) the process
> gets woken up one IRQ period later.
> Ideas why this happens.

this could be a lost RTC IRQ. If you are using 2048 Hz RTC interrupts, it
just needs a single 1msec IRQ delay to lose an RTC IRQ. Especially SCSI
disk interrupts are known to sometimes cause 1-2 millisecs IRQ delays.
But before jumping to conclusions, what exactly are the symptoms, what
does 'one IRQ period later' mean exactly?

-- mingo

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