Messages in this thread | | | Subject | Re: [PATCH 1/3] Separate IRQ-stacks from 4K-stacks option | From | Lee Revell <> | Date | Sun, 12 Sep 2004 15:18:07 -0400 |
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On Fri, 2004-09-10 at 11:34, Arjan van de Ven wrote: > On Fri, Sep 10, 2004 at 05:28:52PM +0200, Andrea Arcangeli wrote: > > On Fri, Sep 10, 2004 at 05:15:38PM +0200, Arjan van de Ven wrote: > > > What we should consider regardless is disable the nesting of irqs for > > > performance reasons but that's an independent matter > > > > disabling nesting completely sounds a bit too aggressive, but limiting > > the nesting is probably a good idea. > > disabling is actually not a bad idea; hard irq handlers run for a very short > time
The glaring exception is the IDE io completion, which can run for 2000+ usec even with a modern chipset and drive. Here's a 600 usec trace:
http://krustophenia.net/testresults.php?dataset=2.6.8-rc4-bk3-O7#/var/www/2.6.8-rc4-bk3-O7/ide_irq_latency_trace.txt
The timer, RTC, and soundcard interrupts (among others) will not like being delayed this long. Ingo mentioned that this was not always done in hardirq context; presumaby the I/O completion was done in a softirq like SCSI. What was the motivation for moving such a long code path into the hard irq handler?
Lee
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