[Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19

Andy Nelson
2005-11-04T17:04:03Z

>On Fri, 4 Nov 2005, Andy Nelson wrote:
>>
>> My measurements of factors of 3-4 on more than one hw arch don't
>> mean anything then?
>
>When I _know_ that modern hardware does what you tested at least two
>orders of magnitude better than the hardware you tested?

Ok. In other posts you have skeptically accepted Power as a
`modern' architecture. I have just now dug out some numbers
of a slightly different problem running on a Power 5. Specifically
a IBM p575 I think. These tests were done in June, while the others
were done more than 2.5 years ago. In other words, there may be
other small tuning optimizations that have gone in since then too.

The problem is a different configuration of particles, and about
2 times bigger (7Million) than the one in comp.arch (3million I think).
I would estimate that the data set in this test spans something like
2-2.5GB or so.

Here are the results:

cpus 4k pages 16m pages
1 4888.74s 2399.36s
2 2447.68s 1202.71s
4 1225.98s 617.23s
6 790.05s 418.46s
8 592.26s 310.03s
12 398.46s 210.62s
16 296.19s 161.96s

These numbers were on a recent Linux. I don't know which one.

Now it looks like it is down to a factor 2 or slightly more. That
is a totally different arch, that I think you have accepted as
`modern', running the OS that you say doesn't need big page support.

Still a bit more than insignificant I would say.

>Think about it.

Likewise.

Andy