The problem most likely stems from the way syscall emulation is
implemented for MP systems. I was trying to enable M5 to run SPLASH
programs compiled for the Tru64 pthreads library, but it turns out that
was much more complicated than I hoped. To run a fully general pthreads
program in SE mode requires implementing a thread scheduler in M5, which
I did not want to do. I was hoping that by restricting the domain to
SPLASH programs where the max number of threads is equal to the number
of processors, it wouldn't be so bad, but it still turned out to have
complications. For example, the Tru64 threads library seems to create
an extra management thread, so even on a 4-CPU system with 4 SPLASH
threads you still have a fifth thread you have to deal with. I thought
I had everything working for the SPLASH benchmarks, but from the problem
you're having it sounds like perhaps with larger numbers of processors
it still breaks. I'm not sure if it always breaks with 16 CPUs or only
for some benchmarks.
Anwyway, there are two directions to go to address this. Given that we
have full-system up, it doesn't make sense to reimplement a major OS
feature like thread scheduling in the simulator. One approach is just
to use the actual OS, i.e., run in full-system mode. The other approach
is to stick with SE mode, but give up on using the pthreads library
underneath the SPLASH macros and define a set of m5-specific calls that
support what the SPLASH benchmarks do but not the full generality of
pthreads (which we don't handle anyway). This is what most other
simulators do. Note that I started down this path already with some of
the synchronization operations. If you want to tackle this latter idea
I could give you some pointers.
Steve
Jeff wrote:
I'm running the Splash-2 benchmarks.
It seems that in ALPHA_SE mode, 16 procs doesn't work.
Do you know what could be the cause of this? I'd like to fix it if possible,
but i just don't know where the problem is or where to start looking for it.
thanks,
jeff
-----Original Message-----
From: Lisa Hsu <[EMAIL PROTECTED]>
Sent: Feb 10, 2006 4:34 PM
To: Jeff <[EMAIL PROTECTED]>
Cc: m5 <[email protected]>
Subject: Re: [m5sim-users] Sampler support in ALPHA_FS
yes, we normally use sampler in full-system mode, though i don't think we've
ever gone up to 16 procs before for experimental purposes. i think at one
point we booted 64 but the kernel spent so much time managing the 64 procs
that no work got done, so that could be really slow and i don't know how
well our linux kernel handles 16 procs.
what kind of benchmarks are you running?
lisa
On 2/9/06, Jeff <[EMAIL PROTECTED]> wrote:
Hi,
I was wondering if it is possible to use the Sampler in full system mode.
I really need to run simulations with 16 or more processors and it seems
that ALPHA_SE doesn't handle that too well when running in detailed mode.
jeff
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