[OT] Linux stability despite unstable hardware

[OT] Linux stability despite unstable hardware

[Timothy Miller]

I have had some issues recently with memory errors when using aggressive 
memory timings.  Although memory tests pass fine, gcc would tend to crash 
and would generate incorrect code when compiling other things. Gcc couldn't 
even build itself properly under those conditions.

The really interesting thing is that the Linux kernel was totally 
unaffected.  Compiling the Linux kernel is often thought of as a stressful 
thing for a system, yet compiling a kernel with a broken gcc on a system 
with intermittent memory errors goes through error free, and the kernel is 
100% stable when running.

But until the memory errors were fixed, things like KDE wouldn't build 
without gcc crashing.

So, what is it about Linux that makes it build properly with a broken GCC 
and run perfectly despite memory errors?

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Re: [OT] Linux stability despite unstable hardware

[Rob Couto]

On Friday 21 May 2004 05:57 pm, you wrote:

> So, what is it about Linux that makes it build properly with a broken GCC
> and run perfectly despite memory errors?

probably just the sources... i built a bunch of gentoo on a flaky machine, and 
ran into trouble with mozilla. it was mozilla 1.6 that demostrated the 
problems and prevented me from continuing to build gnome. i ended up 
rebuilding the whole thing on a speedy box over a weekend, for a far weaker 
architecture that wasn't flaky (despite 4 or 5 brutal soldering adventures on 
the motherboard!!!)

-- 
Rob Couto [rpc@cafe4111.org]
computer safety tip: use only a non-conducting, static-free hammer.
--

Re: [OT] Linux stability despite unstable hardware

[Horst von Brand]

"Timothy Miller" <theosib@hotmail.com> said:
> I have had some issues recently with memory errors when using aggressive 
> memory timings.  Although memory tests pass fine, gcc would tend to crash 
> and would generate incorrect code when compiling other things. Gcc couldn't 
> even build itself properly under those conditions.

Really? memtest86 <http://www,memtest86.com> did finish its run without
errors? I'm sure they'd want to get their hands on the broken RAM...

> The really interesting thing is that the Linux kernel was totally 
> unaffected.  Compiling the Linux kernel is often thought of as a stressful 
> thing for a system, yet compiling a kernel with a broken gcc on a system 
> with intermittent memory errors goes through error free, and the kernel is 
> 100% stable when running.

Sure enough, if the kernel lives (mostly) in unaffected memory, and
furthermore doesn't bang on it quite as hard as a compiler run does (the
kernel only runs for a tiny fraction of the time).
-- 
Dr. Horst H. von Brand                   User #22616 counter.li.org
Departamento de Informatica                     Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria              +56 32 654239
Casilla 110-V, Valparaiso, Chile                Fax:  +56 32 797513

Re: [OT] Linux stability despite unstable hardware

[Steve Dover]

Horst von Brand wrote:
> "Timothy Miller" <theosib@hotmail.com> said:
> 
>>I have had some issues recently with memory errors when using aggressive 
>>memory timings.  Although memory tests pass fine, gcc would tend to crash 
>>and would generate incorrect code when compiling other things. Gcc couldn't 
>>even build itself properly under those conditions.
> 
> 
> Really? memtest86 <http://www,memtest86.com> did finish its run without
> errors? I'm sure they'd want to get their hands on the broken RAM...
> 
Or these days <http:/www.memtest.org/>

Re: [OT] Linux stability despite unstable hardware

[Bryan Andersen]

Timothy Miller wrote:
> I have had some issues recently with memory errors when using aggressive 
> memory timings.  Although memory tests pass fine, gcc would tend to 
> crash and would generate incorrect code when compiling other things. Gcc 
> couldn't even build itself properly under those conditions.
> 
> The really interesting thing is that the Linux kernel was totally 
> unaffected.  Compiling the Linux kernel is often thought of as a 
> stressful thing for a system, yet compiling a kernel with a broken gcc 
> on a system with intermittent memory errors goes through error free, and 
> the kernel is 100% stable when running.
> 
> But until the memory errors were fixed, things like KDE wouldn't build 
> without gcc crashing.
> 
> So, what is it about Linux that makes it build properly with a broken 
> GCC and run perfectly despite memory errors?

It could just be heat buildup in an critical area when under sustained 
heavy load.  It may take a while for enough heat to build up to cause 
problems.  I just recently found one of these.  It would take 4-6 hours 
of heavy intensive processing before an error would happen.  I placed a 
fan pointing at the motherboard chipset and memory to keep them cooler 
and the problem seams to have gone away.

For testing I wrote a script that kept compiling the kernel again and 
agian in a while(true) loop.  Effectively a repeat until crash loop. 
For each compile it saved the stdout/stderr output and diffed it against 
the first run.  Any differnces were flagged for checking latter.

- Bryan

Re: [OT] Linux stability despite unstable hardware

[Jesse Pollard]

On Friday 21 May 2004 16:57, Timothy Miller wrote:
> I have had some issues recently with memory errors when using aggressive
> memory timings.  Although memory tests pass fine, gcc would tend to crash
> and would generate incorrect code when compiling other things. Gcc couldn't
> even build itself properly under those conditions.
>
> The really interesting thing is that the Linux kernel was totally
> unaffected.  Compiling the Linux kernel is often thought of as a stressful
> thing for a system, yet compiling a kernel with a broken gcc on a system
> with intermittent memory errors goes through error free, and the kernel is
> 100% stable when running.
>
> But until the memory errors were fixed, things like KDE wouldn't build
> without gcc crashing.
>
> So, what is it about Linux that makes it build properly with a broken GCC
> and run perfectly despite memory errors?

Been there, seen that too.

I think it has to do with smaller files. This reduces the memory pressure and
the power requirements of the overall system. Once the compiler gets loaded in
memory, it stayes there, small files (without too many includes) keep the
buffer requirements down, and reuses memory that may be better.

I fixed mine by just treating everything as the next lower grade memory 
(switched the BIOS from 60ns to 70ns). I didn't even see a significant
performance reduction either.

[OT] Linux stability despite unstable hardware

[Timothy Miller]

I have had some issues recently with memory errors when using aggressive 
memory timings.  Although memory tests (like memtest86) pass fine, gcc 
would tend to crash and would generate incorrect code when compiling 
other things.  Gcc couldn't even build itself properly under those 
conditions.

The really interesting thing is that the Linux kernel was totally
unaffected.  Compiling the Linux kernel is often thought of as a
stressful thing for a system, yet compiling a kernel with a broken gcc
on a system with intermittent memory errors goes through error free, and
the kernel is 100% stable when running.

But until the memory errors were fixed, things like KDE wouldn't build
without gcc crashing.

So, what is it about Linux that makes it build properly with a broken
GCC and run perfectly despite memory errors?

Re: [OT] Linux stability despite unstable hardware

[Andrew Walrond]

On Friday 21 May 2004 19:04, Timothy Miller wrote:
>
> But until the memory errors were fixed, things like KDE wouldn't build
> without gcc crashing.
>
> So, what is it about Linux that makes it build properly with a broken
> GCC and run perfectly despite memory errors?
>

The linux kernel is all c and assembler, and probably doesn't use too much mem 
during build. Kde on the other hand is all c++ and rather huge. It will 
likely use every bit of ram you have during the build, greatly increasing the 
chances of the memory error hitting you.

But.... Recompile your kernel with the good ram, just in case...