Date: Thu, 1 Dec 2005 12:09:49 -0800 (PST) From: Doug Ambrisko <ambrisko@ambrisko.com> To: Kris Kennaway <kris@obsecurity.org> Cc: freebsd-current@freebsd.org, Darren Pilgrim <dmp@bitfreak.org> Subject: Re: em interrupt storm Message-ID: <200512012009.jB1K9nXq016308@ambrisko.com> In-Reply-To: <20051201200242.GA4197@xor.obsecurity.org>
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Kris Kennaway writes: | On Thu, Dec 01, 2005 at 11:53:00AM -0800, Doug Ambrisko wrote: | > Kris Kennaway writes: | > | On Thu, Dec 01, 2005 at 11:32:10AM -0800, Doug Ambrisko wrote: | > | > On Thursday 24 November 2005 01:27 am, Kris Kennaway wrote: | > | > > On Wed, Nov 23, 2005 at 03:02:05PM -0800, Darren Pilgrim wrote: | > | > > > Until this gets "fixed" in FreeBSD, what should those of us who are | > | > > > effectively stuck with this hardware do to avoid the problem? Does the | > | > > > problem exist in RELENG_4? | > | > > | > | > > Yes, on the same machine I first mentioned. | > | > | > | > Is this is SMP on or off? I think it might be okay if SMP if off. | > | | > | With SMP, I don't recall if I tried it without. SMP is pretty useless | > | on 4.x (often hurts more than it helps), so this may be an acceptable | > | workaround for the OP. | > | > Could you try without SMP? I wonder if the BIOS sets things up okay | > in UP mode. I saw strangeness on our PE2850's in SMP mode that didn't | > happen in UP mode. This is with 4.X. | | Without SMP, the amr and em0 devices are both assigned to irq10. | There does not appear to be an interrupt storm coming from amr | activity (60 interrupts/sec on irq10), but I don't know if this irq | configuration would have stormed anyway, and of course the shared | interrupt is sub-optimal. That seems consistant with what I've seen. FWIW, I have a storm detector in our patched amr driver. If I see more then 500 calls to the interrupt handler per tick then I wait until they slow down. This prevents the death spiral I saw in SMP mode. It looks like we'll be looking into this more since we are seeing problems when adding more NIC's in the box. To date we've been band-aiding the problem. Thanks, Doug A.
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