linux-kernel - Re: Lossy interrupts on x86

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Message-Id: <200709171224.07016.jbarnes@virtuousgeek.org>
Date:	Mon, 17 Sep 2007 12:24:06 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Chris Snook <csnook@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org
Subject: Re: Lossy interrupts on x86_64

On Thursday, September 13, 2007, Chris Snook wrote:
> Jesse Barnes wrote:
> > I just narrowed down a weird problem where I was losing more than
> > 50% of my vblank interrupts to what seems to be the hires timers
> > patch.  Stock 2.6.23-rc5 works fine, but the latest (171) kernel
> > from rawhide drops most of my interrupts unless I also have another
> > interrupt source running (e.g. if I hold down a key or move the
> > mouse I get the expected number of vblank interrupts, otherwise I
> > get between 3 and 30 instead of the expected 60 per second).
> >
> > Any ideas?  It seems like it might be bad APIC programming, but I
> > haven't gone through those mods to look for suspects...
>
> What happens if you boot with 'noapic' or 'pci=nomsi'?  Please post
> dmesg as well so we can see how the kernel is initializing the
> relevant hardware.

noapic gives me the same behavior as nohz=off and pci=nomsi doesn't seem 
to do anything (still get the same lossy interrupts behavior).

dmesg from stock booth (i.e. lossy problem) attached.

Jesse

View attachment "dmesg.txt" of type "text/plain" (27624 bytes)