Hi John,

I suggest using full system mode instead of SE mode if you're running a
multithreaded workload. In FS mode, there's a full OS so it can handle
thread switching, etc. For Parsec on x86 we've created a set of resources
for you to get started. See
https://gem5.googlesource.com/public/gem5-resources/+/refs/heads/stable/src/parsec/
for details.

Cheers,
Jason

On Fri, Apr 16, 2021 at 8:07 AM John Smith via gem5-users <
gem5-users@gem5.org> wrote:

> Hi All,
>
> I am sorry for the confusion.
>
> I am looking to run a multithreaded application on a mesh of 3x3 CPUs,
> where the benchmark spawns 9 threads and each thread runs on
> a single CPU (1:1). I went through the past discussions on this mailing
> list and saw that m5threads was needed to do this. I have some questions.
>
> (1) If there are 9 CPU, and the host CPU launches 9 threads, then are 8
> threads launched on the remaining 8 CPUs and the 9th thread has to wait for
> a
> thread to complete to begin execution. If not then where does it run as
> all the 9 CPUs are currently running a thread (1 host + 8 threads).
>
> (2) Anthony Gutierrez said that m5threads is no longer needed. Is that
> correct for gem5-21 ?
>      (Subject: Simulating multiprogrammed & multithreaded workloads in SE
> mode?)
>
> (3) Right now I am trying to build PARSEC 3.0 benchmarks with m5threads,
> but I am receiving some errors as follows and I am not sure why:
>
>
>
>
>
> *base_dir/local/gcc/bin/gcc -O3 -g -funroll-loops -fprefetch-loop-arrays
>  base_dir/gem5dev/parsec-3.0/pkgs/pthread.o -static-libgcc
> -Wl,--hash-style=both -Wl,--as-needed -DPARSEC_VERSION=3.0-beta-20150206 -o
> siman_tsp siman_tsp.o  -L base_dir/local/gcc/lib64 -L
> base_dir/local/gcc/lib ./.libs/libgslsiman.a ../rng/.libs/libgslrng.a
> ../ieee-utils/.libs/libgslieeeutils.a ../err/.libs/libgslerr.a
> ../sys/.libs/libgslsys.a ../utils/.libs/libutils.a -lpthread
> -lmbase_dir/gem5dev/parsec-3.0/pkgs/pthread.o: In function
> `__pthread_initialize_minimal':pthread.c:(.text+0x97): undefined reference
> to `_dl_phdr'pthread.c:(.text+0xd9): undefined reference to `_dl_phnum'*
>
> Generally how should I go about integrating the m5thread with any
> benchmark?
>
> (4) Also, what other CPU benchmarks are recommended which are
> multithreaded and can be run in a manner where I can
> launch a thread on each CPU ?
>
> Thank You,
> John Smith
>
> <https://www.mail-archive.com/search?l=gem5-users@gem5.org&q=from:%22Gutierrez%2C+Anthony%22>
>
> On Fri, Apr 16, 2021 at 1:50 AM Gabe Black via gem5-users <
> gem5-users@gem5.org> wrote:
>
>> That's essentially right, although gem5 does have some plumbing to run
>> multiple event queues within the same simulation which can coordinate with
>> each other within a small window (quantum) of time. gem5 has support for
>> fibers/threads/coroutines, but these are not typically used to model
>> events. Events are processed inline when they happen using a simple
>> function call.
>>
>> Gabe
>>
>> On Thu, Apr 15, 2021 at 2:46 AM gabriel.busnot--- via gem5-users <
>> gem5-users@gem5.org> wrote:
>>
>>> Hi John,
>>>
>>> Short answer : no, you can only run several simulations in parallel, but
>>> not a single simulation using one thread per CPU.
>>>
>>> Gem5 relies on Discrete Event Simulation (DES) to simulate the
>>> concurrent behavior of HW.
>>> DES is intrinsically sequential in its execution as it relies on
>>> coroutines (also called user user threads, greed threads, fibers, etc.).
>>> Parallelizing such application is a very hard task that often requires a
>>> lot of subtle code transformations to efficiently protect shared resources.
>>> If done correctly, then parallel DES does not have all the good
>>> properties of classic DES, especially determinism... Unless you add extra
>>> care to preserve it, which is hard, too. Trust me ;).
>>>
>>> This question has been discussed back in the days but seems stalled now:
>>> http://www.m5sim.org/Parallel_M5
>>>
>>> Cheers,
>>> Gabriel
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