Re: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel PreemptionPatch

From: Nick Piggin
Date: Fri Jul 23 2004 - 01:47:28 EST

Ingo Molnar wrote:
* Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:

this doesnt work either: once we've committed ourselves to do an
'immediate' softirq processing pass we are risking latencies. We cannot
preempt the idle task while it's processing softirqs the same way we can
do the lock-break if they are always deferred.

It is a preempt off region no matter where it is run. I don't see how
moving it to ksoftirqd can shorten that time any further.

look at my latest patches to see how it's done. We can preempt softirq
handlers via lock-break methods. The same method doesnt work in the idle

Are you referring to this patch?

Surely something similar could easily be done for irq context softirq
processing with a patch like my earlier one? And it would prevent spilling
to ksoftirq when a RT thread isn't waiting to run.

thread. With this method i've reduced worst-case softirq latencies from
~2-4 msecs to 100-200 usecs on a 2GHz x86 box.

Nice numbers.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at