Messages in this thread | | | Date | Thu, 16 Nov 2006 04:21:09 +0100 | From | Andi Kleen <> | Subject | Re: [discuss] Re: 2.6.19-rc5: known regressions (v3) |
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On Wed, Nov 15, 2006 at 12:21:18PM -0800, Andrew Morton wrote: > Andi Kleen <ak@suse.de> wrote: > > > > > > The fact is, it used to work, and the kernel changed interfaces, so now it > > > doesn't. > > > > No, it didn't work. oprofile may have done something, but it > > just silently killed the NMI watchdog in the process. > > That was never acceptable. > > But people could get profiles out. I know, I've seen them!
Just the nmi watchdog was gone then.
> > > Now we do proper accounting of NMI sources and also proper allocation > > of performance counters. > > > > > > > Yes, "oprofile" should be fixed to not depend on that, but the kernel > > > shouldn't change the interfaces, and we should add back the zero entry. > > > > That would break the nmi watchdog again. > > > > Anyways, there is a sysctl to disable the nmi watchdog if someone > > is desperate. > > > > But I think it is clearly oprofile who did wrong here and needs > > to be fixed. > > > > Is it correct to say that oprofile-on-2.6.18 works, and that > oprofile-on-2.6.19-rc5 does not? > > Or is there some sort of workaround for this, or does 2.6.19-rc5 only fail
echo 0 > /proc/sys/kernel/nmi_watchdog before the oprofile module is loaded. With builtin oprofile probably nmi_watchdog=0
> in some particular scenarios?
On x86-64 and on newer i386 machines (based on DMI year)
> > If it's really true that oprofile is simply busted then that's a serious > problem and we should find some way of unbusting it. If that means just > adding a dummy "0" entry which always returns zero or something like that, > then fine.
That could be probably done.
> But we can't just go and bust it.
It just did something unbelievable broken before. I would say it busted itself.
-Andi
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