Isn't it the case that GCC uses pthreads threads as implemented by MinGW? Maybe
I don't understand the architecture but it seems GCC doesn't have Windows
specific thread creating functions. It just uses pthreads and MinGW project
have Windows specific implementation of specific routines. For example:
int
pthread_create (pthread_t *th, const pthread_attr_t *attr, void *(* func)(void
*), void *arg)
is in mingw-w64-libraries\winpthreads\src\thread.c
and as long as it uses _beginthreadex it will never be able to use thread on
another CPU.
Similarly as long as there is this in thread.c in MinGW:
int
pthread_num_processors_np(void)
{
int r = 0;
DWORD_PTR ProcessAffinityMask, SystemAffinityMask;
if (GetProcessAffinityMask(GetCurrentProcess(), &ProcessAffinityMask,
&SystemAffinityMask))
{
for(; ProcessAffinityMask != 0; ProcessAffinityMask >>= 1)
r += (ProcessAffinityMask & 1) != 0;
}
/* assume at least 1 */
return r ? r : 1;
}
GCC itself can't do much about finding more CPUs.
GCC implementation of OpenMP is able to use more than 64 logical CPUs just not
on Windows.
I am new to this. If I could understand the architecture better I might try
fixing it.
On Sat, Jun 16, 2018, at 9:44 AM, Liu Hao wrote:
> 在 2018/6/16 15:38, [email protected] 写道:
> > Counting CPUs is only one problems. You also need to take into account CPU
> > groups when creating threads. The linked docs suggest using
> > CreateRemoteThreadEx instead _beginthreadex. Handling affinity settings
> > becomes more difficult as well (there is scatter, bind etc.). I've seen
> > some code for it in Clang OpenMP source, for example:
> > __kmp_affinity_bind_thread(int proc)
> >
> > It seems Clang also uses system_affinity (_kmp_get_system_affinity) which
> > contains affinities for all CPU groups.
> > Unfortunately I am not competent enough to understand how to do it
> > correctly nor suggest a patch. I have nearly 0 experience in Windows
> > specific programming.
> >
> >
>
> OpenMP is implemented by GCC and consequently out of our control. This
> change will have to be done in GCC code and submitted to GCC developers.
> Hopefully someone will be interested in it.
>
>
> --
> Best regards,
> LH_Mouse
>
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