Re: Performance is weird (fwd)

Manfred Spraul (manfred@colorfullife.com)
Thu, 15 Mar 2001 19:08:03 +0100

One difference between idle and a running user space app is that the
kernel->user space return path checks for pending softirqs, but the ide
thread doesn't.

Perhaps cpu_idle() should also check for pending softirq's before
hlt'ing?

idle thread is running.
* hw interrupt
* * hw interrupt handler
* * * packet arrives
* * * softirq marked
* * hw interrupt handler returns
* do_softirq
* * net_rx called
* * * an hw interrupt interrupts net_rx
* * * * a second packet arrives, softirq marked again.
* * * hw interrupt returns
* * net_rx returns
* do_softirq notices that net_rx is queued again, but doesn't process
it immediately (otherwise it would cause an endless loop)
* hw interrupt returns
idle thread sleeps again.
!! one packet is waiting unprocessed

What about adding if(softirq_active...) do_softirq() into default_idle?

--
    Manfred




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