Messages in this thread | | | Date | Sun, 08 Sep 2002 19:03:28 -0400 | From | Jeff Garzik <> | Subject | Re: [PATCH][RFC] per isr in_progress markers |
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Linus Torvalds wrote: > On Sun, 8 Sep 2002, Zwane Mwaikambo wrote: > >>Here is a newer (untested) patch incorporating Ingo's suggestions as well >>as adding an extra request_irq flag so that isrs can use isr_unmask_irq() >>to enable their interrupt lines. > > > Hmm.. I really don't get the point of what this is supposed to actually > help. > > Clearly, if the device doesn't share the irq line, this doesn't matter. > Similarly, it shouldn't matter if there is just one device that is active > (ie irq line sharing with some slow device where the interrupt happens > fairly seldom). > > As far as I can tell, the only time when this might be an advantage is an > SMP machine with multiple devices sharing an extremely busy irq line. Then > the per-isr in-progress bit allows multiple CPU's to actively handle > several of the devices at the same time.
IMO one should seek to avoid sharing an IRQ line at all. I dunno that you really want to tune for that case, when the user could vastly improve the situation by manipulating IRQs in BIOS setup or similar IRQ-distribution methods.
On an SMP box you especially want to distribute irqs to take best advantage of irq affinity.
Jeff
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