On Mon, 4 Jun 2007, Ray Lee wrote:
On 6/4/07, Jesse Barnes <[email protected]> wrote:
On Sunday, June 3, 2007 2:15:06 Matt Keenan wrote:
> Justin Piszcz wrote:
> > On Sat, 2 Jun 2007, Andi Kleen wrote:
> >>> I feel, having a silent/transparent workaround is not a good idea.
> >>> With that
> >>
> >> If enough RAM is chopped off users will notice. They tend to complain
> >> when they miss RAM. I don't like panic very much because for many
> >> users it will be a show stopper (even when they are not blessed
> >> with "quiet" boots like some distributions do)
> >>
> >> The message in dmesg could be also emphasized a bit with a little
> >> ASCII art (but no <blink> tag in there)
> >>
> >> The problem I'm more worried about is if the system will be really
> >> stable --- could it be that the memory controller is still
> >> misconfigured and cause other stability issues? (we've had such
> >> cases in the past). Also I'm not sure we can handle the case of
> >> the MTRR wrong not at the end of memory but at the hole sanely.
> >>
> >> -Andi
> >
> > So far I have been booting with mem=8832M and have run stress/loaded
> > the memory subsystem pretty good; what other tests should I run?
> >
> > It'd be nice if we could pose some sort of solution/warning for the
> > future so other people do not have to experience the same problems.
> >
> > What are the next steps?
>
> Wouldn't it be possible for the e820/MTRR set up code detect the problem
> and suggest a mem=xxxx that would fix the problem (while also
> complaining that the BIOS is broken)?
Yes, that should be fairly easy, though as Andi points out, if there are
holes
in the MTRR setup, things get a little trickier (I had an earlier patch to
deal with this, but ended up with too many early boot issues).
Maybe what Venki suggested would be best: just detect the condition and
panic, with a string telling the user to use mem=xxx (we can figure that
out)
and/or upgrade their BIOS.
Ick. Systems that used to boot fine would then panic on a kernel
upgrade. That's rather rude for a condition that's merely an
optimization (using all memory), rather than one of correctness. A
panic seems entirely inappropriate.
Ray
While I am unsure of the 'best' solution, if they boot and it does not
panic but takes 10 minutes to boot, people are going to seriously wonder
what is going on?
Justin.
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