Re: Problem with Gdt driver under smp?

[Pedro Pla <pedropla@holidaymarketing.com>]

Doug Ledford wrote:

>On Tue, Nov 05, 2002 at 06:01:37PM +0800, Pedro Pla wrote:
>  
>
>>Been running the script all day and still no errors yet, and yes, it 
>>seems to have used up all the memory or so says a cat /proc/meminfo with 
>>only a few megs free and no swap activated. This is under a no smp 
>>compiled kernel, under an smp compiled kernel I think it could die while 
>>ungzipping the first source directory.. yeah it's that bad, no "subtle" 
>>problem, just an asap kernel oops or segmentation fault.. can't switch 
>>to mp 1.1 from mp 1.4 on this motherboard either, or at least I haven't 
>>found out how yet, it's an intel scb2, intel says nothing about how to 
>>do so on their sites, and the bios has no such option... at least the 
>>machine runs flawlessly all tests in non-smp mode which makes me think 
>>it isn't hardware..
>>    
>>
>
>Why would you think that?  You don't really think that the linux kernel 
>SMP support is so flaky that it can't survive the first round of 
>ungizzipping on an SMP machine do you?  I mean, after all, millions of SMP 
>boxes are out there running the linux kernel every day without a glitch.  
>If the kernel were that bad, they would *all* be dying.
>
Of course not :) I have been running linux smp machines for nearly 4 
years, since I had to compile the smp support in by putting the smp = 1 
manually ;) and it has been a breeze, that's why initially I did think 
it was definately a hardware issue, however these are "branded" machines 
and I have tried two different setups with the same kind of peices 
(identical cpu's, ram, motherboard, raid controller, etc) and both have 
failed. Yes it could be a fundamental flaw in the design or build of 
both of these machines, although that is a little out of the ordinary, 
that is why I suspected it might be some flaw somewhere in the kernel 
that gave it a hard time running on this particular setup. Or maybe a 
design flaw in the hardware that makes it not run correctly under linux? 
However all this hardware is certified to run under Redhat by both the 
manufacturer intel, and Redhat...

>  OTOH, several 
>things on the motherboard change when running SMP mode.  Power consumption 
>goes up (so a bad power supply can cause these problems), you start using 
>a CPU that isn't being used now (so a totally busted CPU could cause this, 
>swapping CPU sockets might make it start failing in UP mode as well), 
>amount of data your are pumping to RAM from CPU goes up (because you have 
>two CPUs pumping data instead of one, and if the memory controller or 
>cache coherency controller or RAM itself can't handle the increased speed 
>of data throughput you get all sorts of errors), etc.  There are *tons* of 
>things that change going from UP to SMP in the hardware and all sorts of 
>things that used to work fine can start breaking.  The fact that your 
>machine works OK in UP mode means absolutley nothing about how it will 
>work in SMP mode or whether or not the hardware is up to running SMP.
>
>  
>
Point taken, I will wait till I receive the other 4 machines with 
identical configurations, and if each and every one fails under smp mode 
must I still think it is hardware? that would be 6 seperate machines 
with identical configurations failing in smp? These are all pure intel 
except ram and hard disks. Although I did read on the intel site that 
the raid controller scrmr had problems with the scb2 motherboard, and I 
did apply the bios upgrade, but it still fails... sigh... maybe I should 
find a less stressful profession ;) after being on comps for 12 years 
you wonder just what more can fail when you are pressed for time and 
bosses are looking over your shoulder ;)