Hi Maryam,
You need to tell the simulator how many thread contexts it needs at the
beginning of execution. There's no thread scheduler in SE mode like there'd be
in a real operating system. Since clone allows you to dynamically create a lot
of processes, they need to be bound to thread contexts. Since the simulator
doesn't know how many the application needs you need to tell it.
Pass in the -n option to the configs/example/se.py script. You could try
something like -n4 or w/e.
Regards,
Brandon
-----Original Message-----
From: gem5-dev <gem5-dev-boun...@gem5.org> On Behalf Of Maryam Babaie
Sent: Monday, March 18, 2019 1:56 PM
To: gem5 Developer List <gem5-dev@gem5.org>
Subject: Re: [gem5-dev] Syscall_Emulation for Shared Memory
Hi all,
I tried a simple program for testing clone system call on gem5 (SE mode, X86).
Eventhough clone is implemented in the list of system calls, via
cloneFunc<X86Linux64>; but it works like it's not implemented!
As I checked clone system call always returns in the if clause at
src/sim/syscall_emul.hh:1519 :
if (!(ctc = p->findFreeContext())) {
DPRINTF_SYSCALL(Verbose, "clone: no spare thread context in system"
"[cpu %d, thread %d]", tc->cpuId(), tc->threadId());
return -EAGAIN;
}
Obviously, the reason it returns originates from "ctc =
p->findFreeContext()", in which "findFreeContext()" returns nullptr,
p->but I
cant' figure out why it happens.
I appreciate if any one shares their insight in this regard.
Bests,
MB
On Mon, Mar 11, 2019 at 3:39 PM Potter, Brandon <brandon.pot...@amd.com>
wrote:
> Hi Maryam,
>
> The code that you are looking at is going to change soon. There is a
> changeset on the google reviewboard which will add some fidelity to
> the tracing of mmap/munmaps from the perspective of SE mode (
> https://gem5-review.googlesource.com/c/public/gem5/+/12307). Feel free
> to review it if it's interesting to you.
>
> 1) I don't understand what you are asking.
> 2) The new patch has an implementation.
> 3) We could probably add an implementation that flushes file-backed
> mmaps to the host file. I have never run into a situation where this
> was needed in an application that was being simulated (so it doesn't
> have an implementation).
> 4) It turns out that fork is not used in Linux to create a new
> process. It uses the clone system call instead. (You can verify this
> by using the Linux strace command with your application. You should
> only see a clone call.) You should take a look at the clone implementation.
>
> Regards,
> Brandon
>
> -----Original Message-----
> From: gem5-dev <gem5-dev-boun...@gem5.org> On Behalf Of Maryam Babaie
> Sent: Friday, March 8, 2019 4:06 PM
> To: m5-...@m5sim.org
> Subject: [gem5-dev] Syscall_Emulation for Shared Memory
>
> Hi all,
> I have some questions regarding the system calls available in SE mode
> on
> gem5 for X86. I appreciate if any one shares their insight about them:
>
> 1. For the mmap syscall, the function "mmapImpl" has been implemented.
> Up-to which extend this function will work properly for mmap syscall?
>
> 2. For munmap syscall, they have put the munmapFunc, but the body of
> the corresponding function is actually empty. So, does this mean it is
> actually not supported on gem5?
>
> 3. msync syscall is flagged as unimplementedFunc. So, does this mean
> that mmap will still work but the writes will not be reflected
> persistently in the region?
>
> 4. Since the fork syscall is also flagged as unimplementedFunc , how
> is the concept of Copy on Write (generally shared pages) able to be
> simulated and handled in gem5?
>
> Regards
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