Date: Tue, 22 Nov 2005 20:54:49 -0800 (PST) From: John Polstra <jdp@polstra.com> To: Kris Kennaway <kris@obsecurity.org> Cc: current@freebsd.org, net@freebsd.org Subject: RE: em interrupt storm Message-ID: <XFMail.20051122205449.jdp@polstra.com> In-Reply-To: <20051123030304.GA84202@xor.obsecurity.org>
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On 23-Nov-2005 Kris Kennaway wrote: > I am seeing the em driver undergoing an interrupt storm whenever the > amr driver receives interrupts. In this case I was running newfs on > the amr array and em0 was not in use: > > 28 root 1 -68 -187 0K 8K CPU1 1 0:32 53.98% irq16: em0 > 36 root 1 -64 -183 0K 8K RUN 1 0:37 27.75% irq24: amr0 > ># vmstat -i > interrupt total rate > irq1: atkbd0 2 0 > irq4: sio0 199 1 > irq6: fdc0 32 0 > irq13: npx0 1 0 > irq14: ata0 47 0 > irq15: ata1 931 5 > irq16: em0 6321801 37187 > irq24: amr0 28023 164 > cpu0: timer 337533 1985 > cpu1: timer 337285 1984 > Total 7025854 41328 > > When newfs finished (i.e. amr was idle), em0 stopped storming. > > MPTable: <INTEL SE7520BD22 > This is the dreaded interrupt aliasing problem that several of us have experienced with this chipset. High-numbered interrupts alias down to interrupts in the range 16..19 (or maybe 16..23), a multiple of 8 less than the original interupt. Nobody knows what causes it, and nobody knows how to fix it. John
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