computation-friendly kernels

[Alexander Dalloz]

Am Do, den 08.01.2004 schrieb Bevan C. Bennett um 19:38:
> I suspect a full answer to this may be too involved for this list, but 
> maybe someone a little more into kernel hacking than I've been lately 
> could point me in the right direction.
> 
> I have two identical servers, one running FC1 and one running severn 
> (RHEL3beta). The installed kernels are:
> 
> kernel-smp-2.4.22-1.2138.nptl (FC1)
> kernel-smp-2.4.21-1.1931.2.399.ent (severn)

You mean not Severn, which was a Fedora beta, but you mean Taroon. I
just checked that over the kernel version you give and that matches.

> I have a very highly multithreaded application that runs generally 4x 
> slower on FC1, but occassionally takes 20x as long. Interestingly, the 
> "user" time in all cases is very consistant, and on the non-FC1 system 
> real time is only fractionally higher than user time.  So... I suspect 
> that there's some kernel parameter, memory management scheme or 
> scheduling configuration difference causing the performance disparity.

4 times up to 20 times faster on Taroon compared to Fedora Core 1 is
amazingly. Are you running one specific multithreaded application or a
set of those? How do you measure the time it takes - by "time program"?

> My question is whether there's any hope of discovering which difference 
> is involved and 'fixing' the FC1 system (or even of easily enumerating 
> what the differences actually are)?

The RHEL kernel is very optimized for big machines with much RAM,
multiprozessors and so on. Can you describe your machine park a little
bit?

> I know that FC is aimed more at a desktop/general user release (and is 
> the best Linux I've used so far for that purpose), and that ideally I'd 
> help support RedHat by purchasing 100 copies of RHEL for my heavy 
> computing, but there are unfortunate budgetary forces involved that 
> prohibit that at the moment. If the company situation improves, that's 
> the way I'd like to go eventually.
> 
> I'm willing to compile custom kernels for a 4x speedup and better 
> consistancy, but I'd like to keep the number of different distributions 
> in active use to a minimum (every different distribution adds more work 
> in creating and maintaining compatible configuration info).
> 
> Any informed suggestions from the community?

Maybe you should post you question on the fedora-devel list. It seems
the Redhat folks are paying there more attention to such questions than
here.

Regards

Alexander


-- 
Alexander Dalloz | Enger, Germany
PGP key valid: made 13.07.1999
PGP fingerprint: 2307 88FD 2D41 038E 7416  14CD E197 6E88 ED69 5653