Re: [Gems-users] very slow performance

[Dan Gibson <degibson@xxxxxxxx>]

ls might seem like a simple command, but it may end up sending disk requests if you are ls-ing a part of your file system that isn't in the target's OS FS cache. Ruby will, of course, do its best to faithfully model the memory system for the duration of a disk access or two, which would be quite a long time.

Regards,
Dan

Thomas De Schampheleire wrote:

Hi, it is normal that there are significant slowdowns when simulating
with gems. I have posted some results of my own in the following
thread:
https://lists.cs.wisc.edu/archive/gems-users/2007-March/msg00075.shtml

In order to simulate a second (75000000 cycles) on a 4-processor
(75MHz) sarek/serengeti machine running OpenSolaris b57, it took me
about 2 hours. If we assume that we can scale the runtime linearly
with the number of processors, extrapolating that to 16 processors
would take 8 hours.
These tests are with a cpu-switch-time of 1, and ran on a Intel Core
Duo (2x1.66 GHz) with 1GB of DDR2 RAM.

You can speedup simulation quite a bit using a higher cpu-switch-time,
for example 1000 or 10000. This will loose some accuracy in the
timing, but maybe you don't need that.

Thomas

On 4/13/07, Fengguang Song <song@xxxxxxxxxx> wrote:
  

Hi,

I've tried to build a 16 CPU system. There was no problem
when following the QuickStart document. But it is extremely
slow, an "ls" command takes about 40 minutes.
A small system with 1 CPU took a couple of seconds to run "ls".

I only loaded the ruby module. Without ruby, simics runs
pretty fast even on the 16-cpu system (for "ls").
I'm wondering if I run a one-minute program, the simulation
might take several days. Is it normal, or it is just related
to Solaris console? Is there anything I could do to make it
run faster?

As ruby reported, 208669177 instructions (for "ls" command)
took 42.6038 minutes (~81KIPS). Is the number normal?

Here is the machine I'm using:
OS: Red Hat AS4
Processor: 4x3.0Ghz Intel Core 2 Duo
Ram: 4G

Thanks much,
Fengguang
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