Messages in this thread | | | Date | Sun, 11 Jan 2004 11:50:12 -0500 | From | Joe Korty <> | Subject | Re: 2.6.1 and irq balancing |
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On Sun, Jan 11, 2004 at 10:51:22AM +0100, Arjan van de Ven wrote: > On Sun, 2004-01-11 at 00:14, Ethan Weinstein wrote: > > Greetings all, > > > > I upgraded my server to 2.6.1, and I'm finding I'm saddled with only > > interrupting on CPU0 again. 2.6.0 does this as well. This is the > > Supermicro X5DPL-iGM-O (E7501 chipset), 2 Xeons@2.4ghz HT enabled. > > /proc/cpuinfo is normal as per HT, displaying 4 cpus. > > you should run the userspace irq balance daemon: > http://people.redhat.com/arjanv/irqbalance/
I have long wondered what is so evil about most interrupts going to CPU 0 that we felt we had to have a pair of irqdaemons in 2.6. From my (admittedly imperfect) experience, the APIC will route an interrupt to CPU 1 if CPU 0 is busy with another interrupt, to CPU 2 if 0 and 1 are so occupied, and so on. I see no harm in this other than the strangely lopsided /proc/interrupt displays, which I can live with.
Earlier APICs had a variation where the search for where each new interrupt was to go started with first cpu after the one that got the last interrupt. If we call this 'round-robin' allocation, then today's technique could be described as 'first fit'.
If I am wrong about this, I would dearly love to be corrected :) Joe - 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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