[parsec-users] Simulation time of "facesim" and "vips"

Muhammad abid Mughal mabidm_pieas at yahoo.com
Tue Jun 1 20:58:34 EDT 2010


Thank you very much for your detailed answer. I really appreciate your time.

Take Care

Best Regards,
Muhammad abid



________________________________
From: Jim Dempsey <jim at quickthreadprogramming.com>
To: PARSEC Users <parsec-users at lists.cs.princeton.edu>
Sent: Tuesday, June 1, 2010 22:16:09
Subject: Re: [parsec-users] Simulation time of "facesim" and "vips"

 
Oops, make that "Back in the early 1970's..." (1972 
actually)
 


________________________________
 From: parsec-users-bounces at lists.cs.princeton.edu 
[mailto:parsec-users-bounces at lists.cs.princeton.edu] On Behalf Of Jim 
Dempsey
Sent: Tuesday, June 01, 2010 8:09 AM
To: 'PARSEC 
Users'
Subject: Re: [parsec-users] Simulation time of "facesim" and 
"vips"


>>As far as I understand your response you are asking me to 
Optimize I/O of "facesim" and "vips" using actual and virtual 
time.
 
Back in the late 1960's when I worked at Digital 
Equipment Corporation I used a simulator on their PDP10 that would simulate a 
PDP8-I computer system including all the I/O devices. The computer being 
simulated was single core and therefore the virtual time was elastic. By this I 
mean I/O wait time could be simulated, or estimated, or instantaneous 
(immediately complete in virtual system).
 
The simulator 
you use simulates multi-core systems. Not being a user of this system, I can 
only hypothesize. 
 
The simulator 
you use:
 
    may
    may not
   
 or have option to control
 
simulation of 
disk level I/O. If your simulator (settings) present a fully accurate disk 
sub-system, then the I/O wait time by one thread is not elastic. Meaning the 
virtual I/O wait time by one simulated core is available run time for remaining 
simulated cores (and available for the I/O initiating core since the initiating 
software thread is likely context switched out). If your simulator is executing 
at, for example, 1/100th the rate a real system operates at, then I/O operations 
on physical system that takes 8ms will consume wall clock time of 800ms. The 
actual consumption will depend on the difference between your wall clock time 
and virtual time (i.e. performance of simulator).
 
Check your 
documentation to see if the I/O wait time is tunable. (or choose to simulate a 
SSD or RAM-disk)
 
The point I 
was making is if you can set a tuning parameter to eliminate I/O wait time, then 
you may also wish to accumulate the physical I/O wait time when you run stand 
alone, and accumulate the virtual no wait I/O wait time (likely non-zero). With 
the two lists at hand you can now re-adjust the results data for a better 
estimate on the relative performance. This won't be completely accurate, but it 
may be a better estimate of the virtual performance.
 
Also, with 
the list of timestamp differentials in your real simulation, and knowing the 
simulation rate of facsim in your simulation, you can now let your simulation 
run for ? 8 hours (you pick convenient time), extract the number of iterations 
of the major loop, then extrapolate the completion time. This will be a rough 
estimate which is better than no estimate.
 
Jim 
Dempsey
 
 
 


________________________________
 From: parsec-users-bounces at lists.cs.princeton.edu 
[mailto:parsec-users-bounces at lists.cs.princeton.edu] On Behalf Of Muhammad abid Mughal
Sent: Tuesday, June 01, 2010 12:35 
AM
To: PARSEC Users
Subject: Re: [parsec-users] Simulation 
time of "facesim" and "vips"


Hi Jim Dempsey,    
               
          Thanks for quick response.
I have already successfully run "facesim" and "vips" 
using "parsecmgmt -a run -p vips -c gcc-hooks -i simsmall -n 8 -x pre-simics" 
command on
    my real sun machine  and 
simulated machine inside simics (ie functonal simulation).In addition, i 
disabled all SMF services of solaris 10 inside my 
simulated machine so that these services don't interfere 
with my PARSEC benchmark.

As far as i understand your response you are asking me to 
Optimize I/O of "facesim" and "vips" using actual and virtual time.

My simulated machine is 8-chip 
distributed shared memory machine and i am working on prefetching/memory 
streaming using Hardware Prefecher.
I am confused because i was 
planning to run simulations using "simmedium" data set but i would not be 
possible because of simulation speed.

I am wondering if i increase 
number of threads for facesim and vips to finish simulation quickly. Any more 
suggestion.


Regards,
Muhammad 
abid
  



________________________________
 From: Jim Dempsey 
<jim at quickthreadprogramming.com>
To: PARSEC Users 
<parsec-users at lists.cs.princeton.edu>
Sent: Tuesday, June 1, 2010 
11:39:56
Subject: Re: 
[parsec-users] Simulation time of "facesim" and "vips"

 
Muhammad,
 
Have you verified first that your configuration runs well in 
native mode on an x86 processor? This is to make sure your input data and 
command line arguments are correct. And will give you a base line measurement 
for a given processor model.
 
The next thing to do is look at the major loop in facesim to 
see if you can instrument that in native mode. e.g. on the native mode run, use 
RDTSC (or other high precision timer) and record the time intervals for each 
iteration of the major loop. After you have this collection of times (convert to 
seconds) then recode to use a virtual timer in your simulation mode, however 
also modify the simulator such that you get progress information such as the 
virtual time elapsed .AND. the actual time elapsed at each major loop interval. 
Now then instead of running simulation to end of benchmark program, you can run 
the simulation for as many iterations as you deem practical and which provides 
the timing information you want.
 
Also, while you are adding your RDTSC insturmentation, measure 
the time for each file I/O. Then you can use this data to normalize the I/O 
within the simulator.
 
Jim Dempsey
 


________________________________
 From: parsec-users-bounces at lists.cs.princeton.edu 
[mailto:parsec-users-bounces at lists.cs.princeton.edu] On Behalf Of Muhammad abid Mughal
Sent: Monday, May 31, 2010 8:32 
PM
To: Parsec group
Subject: [parsec-users] Simulation time 
of "facesim" and "vips"


Hi guys/Chris,
                     
   Hope you all doing good. I am running timing simulation of 
above-said benchmarks using "simsmall" data set.
But its been running for almost 7 days. Is there anyway to reduce this huge 
simulation time for these benchmarks without compromising on the performance 
measurement accuracy? ie performance measurement must be representative of the 
work done by these benchmarks.

i find it hard to switch to another Simulator fast simulator (ie Flexus) . 
I am using GEMS simulator.



Regards,
Muhammad abid

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.cs.princeton.edu/pipermail/parsec-users/attachments/20100601/f6a61124/attachment.html>


More information about the parsec-users mailing list