Messages in this thread | | | Date | Mon, 13 Sep 2004 16:26:43 -0400 | From | Bill Davidsen <> | Subject | Re: [PATCH 1/3] Separate IRQ-stacks from 4K-stacks option |
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Lee Revell wrote: > 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?
Certainly if you run ppp the serial port won't like being ignored that long, and if you pull down data on a parallel port that really won't like it. The soundcard is probably only a problem if you're recording input, in spite of some posts here about skipping, the world doesn't end if you get a skip, although 2ms shouldn't cause that anyway.
-- bill davidsen <davidsen@tmr.com> CTO TMR Associates, Inc Doing interesting things with small computers since 1979 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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