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Subject: Re: Linux SMP

Author: Vincent Diepeveen

Date: 11:43:49 09/01/03

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On August 31, 2003 at 20:38:23, Russell Reagan wrote:

For many cpu's, IRIX is by far superior.

Linux support is improving day by day. Matter of time before kernel 2.6 will
work great.

Windows 2003 server is not so bad until a cpu or 8, if you can afford it.
On paper it runs till 64 cpu's or so. I do not know whether it still runs a
program then on cpu0 then on cpu 5 then on cpu 3. If it doesn't do that anymore
it will be fine.

Solaris is very stable OS, but it is not a NUMA system let's not forget it.

I guess your professor doesn't know much about NUMA other than what it is in
theory.

if you get solaris usually you'll get a slow 1Ghz cpu from Sun with it for
$$$$$. usually those cpu's execute 1 instruction a clock.

In 2004 they will come with a new cpu, using an old ultrasparc II core.
dual core 1Ghz. with a maximum of 1 instruction a cpu.

Sun stands for stability. They are more stable than linux and hot swappable
cpu's and such.

Very good for telecommunication.

SGI with irix is the only OS capable of running very good at cc-NUMA systems at
massive amounts of CPU's.

I will not comment on how stable or unstable it is. That would not be
appropriate. There is so little of those machines build that trivially each one
has their own diseases.

But let's compare prices.

16 processor SUN until not too long ago that was $10 million
64 processor SGI itanium2-madison 1.3Ghz - $1 MLN

Then you get linux 2.4.20-220r3 SGI kernel with it.

Irix will NOT be ported to itanium platform. Most likely only to opteron
platforms (Cray etc).

It is very hard to judge OSes without having worked with them.

I found working with ultrasparcs not so easy. The OS isn't very easy to use.
Linux is way easier than solaris to work with. Linux also way easier than IRIX.

I have worked veyr little with AIX so i could not comment on that, don't even
know whether it still gets used a lot. My memory is very good, but i'm not doing
effort to remember all the linux/unix/irix/solaris commands.

In that case solaris is hell to work with.

It may be very stable, which is important for an OS, and it may be hot
swappable, but it would be the last OS i would chose as my favourite one.

Windows has the DLL problem of course. Every product installs its own DLLs which
makes it instable.

Apart from that windows is by far superior to work with. Not so secure. Not so
stable, but far superior for the average user.

After that linux is by far superior to everything. It is a matter of time before
it will work very well at big systems too. It runs till 64 processors now and it
isn't doing it too bad.

Still major bugs in knowing where to schedule which process and how at cc-NUMA
machines. That requires knowledge of the architecture and in the linux world
they typically are not busy with that kind of stuff.

So i'm not sure whether kernel 2.6 will beat IRIX ever on such systems.

So where thanks to the hardware irix might not look superstable, as every few
months it needs a reboot for sure, for latency issues and such it is far
superior.

Good example is the latency measured at the new SGI systems with linux kernel.

If nothing runs there it is for 8 cpu's around 600 ns latency till 8 cpu's. on
average.

If something else runs , just 12 cpu's, then it's 1.0 us already.

16 cpu's 1.2 us.

IRIX there still achieved 800ns- 900 ns in both cases.

So from performance viewpoint nothing beats IRIX.

Solaris at a 8 processor SUN gives already 900ns. that's shared bus.

But of course hardware dependant.

Sun runs till 128 cpu's but that's shared bus. no comparision possible with
other oses.



>In a unix system administration class today, the professor said that the SMP
>support in Linux isn't very good. He said it's okay if you're doing 2x or maybe
>4x, but he said that anything higher than that and you should use something like
>Solaris, and gave the impression that Solaris was a very solid choice for an SMP
>machine.
>
>I was suprised that he said this, because (IIRC) Dr. Hyatt uses Redhat Linux,
>and he doesn't seem to think very highly of Sun, and he obviously knows a
>"little" about all things SMP ;-)
>
>I have a few questions in regards to how different operating systems compare in
>terms of SMP support.
>
>Which operating systems are preferred?
>
>Which operating systems should be avoided?
>
>How is Windows?
>
>How is FreeBSD? I heard Gian-Carlo saying something about FreeBSD not having
>good multithreaded support.
>
>If Linux has sub-par SMP support, will this be improved in kernel 2.6?



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