Hi!

On 2022-07-07T23:18:03+0100, Andrew Stubbs <ams@codesourcery.com> wrote:
> On 07/07/2022 12:54, Tobias Burnus wrote:
>> On 07.07.22 12:34, Andrew Stubbs wrote:
>>> Implement the -foffload-memory=pinned option such that libgomp is
>>> instructed to enable fully-pinned memory at start-up.  The option is
>>> intended to provide a performance boost to certain offload programs
>>> without
>>> modifying the code.
>> ...
>>> gcc/ChangeLog:
>>>
>>>     * omp-builtins.def (BUILT_IN_GOMP_ENABLE_PINNED_MODE): New.
>>>     * omp-low.cc (omp_enable_pinned_mode): New function.
>>>     (execute_lower_omp): Call omp_enable_pinned_mode.
>>>
>>> libgomp/ChangeLog:
>>>
>>>     * config/linux/allocator.c (always_pinned_mode): New variable.
>>>     (GOMP_enable_pinned_mode): New function.
>>>     (linux_memspace_alloc): Disable pinning when always_pinned_mode set.
>>>     (linux_memspace_calloc): Likewise.
>>>     (linux_memspace_free): Likewise.
>>>     (linux_memspace_realloc): Likewise.
>>>     * libgomp.map: Add GOMP_enable_pinned_mode.
>>>     * testsuite/libgomp.c/alloc-pinned-7.c: New test.
>>> ...
>> ...
>>> --- a/gcc/omp-low.cc
>>> +++ b/gcc/omp-low.cc
>>> @@ -14620,6 +14620,68 @@ lower_omp (gimple_seq *body, omp_context *ctx)
>>>     input_location = saved_location;
>>>   }
>>> +/* Emit a constructor function to enable -foffload-memory=pinned
>>> +   at runtime.  Libgomp handles the OS mode setting, but we need to
>>> trigger
>>> +   it by calling GOMP_enable_pinned mode before the program proper
>>> runs.  */
>>> +
>>> +static void
>>> +omp_enable_pinned_mode ()
>>
>> Is there a reason not to use the mechanism of OpenMP's 'requires'
>> directive for this?

I agree.  (But I'm not working on that, for avoidance of doubt.)

>> (Okay, I have to admit that the final patch was only committed on
>> Monday. But still ...)
>
> Possibly, I had most of this done before then. I'll have a look next
> time I visit this patch.

Until then, let's at least document/verify 'GOMP_enable_pinned_mode';
I've pushed to devel/omp/gcc-12
commit 9657d906869e098340c23118c2eb8592d9e77ac5
"Prototype 'GOMP_enable_pinned_mode'", see attached.


Grüße
 Thomas


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