Re: Linux scalability?

Dan Kegel
2001-05-18T18:04:11Z

Sasi Peter <sape@iq.rulez.org> wrote:
> I am just writing an essay, an have mentioned TUX as a performance and
> scalability linearity recort holder with TUX, referencing the specweb99
> website summary page:
>
> http://www.spec.org/osg/web99/results/web99.html
>
> However, taking a closer look, it turns out, that the above statement
> holds true only for 1 and 2 processor machines. Scalability already
> suffers at 4 processors, and at 8 processors, TUX 2.0 (7500) gets beaten
> by IIS 5.0 (8001), and these were measured on the same kind of box!
>
> How come, TUX is soooo good at the lowend (1 and 2 CPUs), and scales this
> bad?

Let's look at the scores. (BTW, SPECweb99 gets harder
as the scores get better; the document tree required to achieve a score of
3222 is twice as large as that required to achieve a score of 1438.)

SPECweb99 result summary:
date #cpu #nics L2 cache/cpu RAM tree score sw model MHz
1/2001 1 1 256K 2G 5G 1438 tux2 Compq Proliant DL320 800
6/2000 1 1 256K 2G 4G 1270 tux1 Dell Poweredge 6400 667
6/2000 2 2 256K 4G 7G 2200 tux1 Dell Poweredge 4400 800
3/2001 2 4 256K 4G 10G 3222 tux2 Dell Poweredge 2500 1000

2/2001 1 3 2M 8G 9G 2700 tux2 IBM xSeries 370 900
2/2001 2 4 2M 16G 13G 3999 tux2 IBM xSeries 370 900
6/2000 4 4 2M 8G 14G 4200 tux1 Dell Poweredge 6400 700
7/2000 8 8 2M 32G 21G 6387 tux1 Dell Poweredge 8450 700
11/2000 8 8 2M 32G 24G 7500 tux2 Dell Poweredge 8450 700
12/2000 8 8 2M 32G 21G 6407 tux1 IBM Netfinity 8500R 700

3/2001 2 3 256K 4G 8G 2499 IIS5/SWC HP NetserverLP2000r 1000
4/2001 8 8 2M 32G 26G 8000 IIS5/SWC Dell Poweredge 8450 700

IIS5/SWC only has two results on record, at 2 and 8 CPUs. They're hard
to compare, because they have different cache and RAM sizes and CPU speeds,
but it's safe to say that it performs poorly at 2 CPUs (compared to the 3/2001
results from Dell) and scales nearly linearly to perform comparatively well at 8 CPUs.

Looking at the IBM 1 and 2 CPU results, twice the CPU only got 1.4 times
the performance. Not sure TUX is scaling especially well even at 2 CPU's.
(And you can't blame this on disk drives, please don't try.)

So I agree, Tux doesn't seem to scale as well to multiple CPUs as does IIS5/SWC.

About comparing the Tux and IIS/SWC results on the Dell 8 CPU box:
the Tux measurement is 5 months older than the IIS/SWC measurement.
It's interesting to speculate how tux2 would do if tested today;
It looks like tux2 is about 12% faster than tux1 on 8-CPU machines.
In other words, 5 months of further development on tux and the 2.4 kernel yielded
a 12% speedup. Since IIS was only 4% faster than TUX, If Tux were measured today,
it might have improved enough to beat IIS/SWC, who knows.

- Dan