Hi!

On 2021-07-27T12:01:18+0200, I wrote:
> On 2021-06-29T16:42:03-0700, Julian Brown <julian@codesourcery.com> wrote:
>> This patch fixes several places in libgomp/target.c where "ephemeral" data
>> (on the stack or in temporary heap locations) may be used as the source of
>> an asynchronous host-to-device copy that may not complete before the host
>> data disappears.  Versions of the patch have been posted several times
>> before, but this one (at Chung-Lin Tang's prior suggesion, IIRC) moves
>> all logic into target.c rather than pushing it out to each target plugin.
>
> Thanks for the re-work!

>> +/* Copy host memory to an offload device.  In asynchronous mode (if AQ is
>> +   non-NULL), when the source data is stack or may otherwise be deallocated
>> +   before the asynchronous copy takes place, EPHEMERAL must be passed as
>> +   TRUE.  The CBUF isn't used for non-ephemeral asynchronous copies, because
>> +   the host data might not be computed yet (by an earlier asynchronous compute
>> +   region).  */
>> +
>>  [gomp_copy_host2dev]
>
> Code changes related to the latter sentence have moved into a separate
> "Don't use libgomp 'cbuf' buffering with OpenACC 'async'", pushed to
> master branch in commit d88a6951586c7229b25708f4486eaaf4bf4b5bbe, [...]

Re this TODO comment:

> +   TODO ... but we could allow CBUF usage for EPHEMERAL data?  (Open question:
> +   is it more performant to use libgomp CBUF buffering or individual device
> +   asyncronous copying?)  */

Pushed to master branch commit 2b2340e236c0bba8aaca358ea25a5accd8249fbd
"Allow libgomp 'cbuf' buffering with OpenACC 'async' for 'ephemeral' data",
see attached.


Grüße
 Thomas


-----------------
Siemens Electronic Design Automation GmbH; Anschrift: Arnulfstraße 201, 80634 München; Gesellschaft mit beschränkter Haftung; Geschäftsführer: Thomas Heurung, Frank Thürauf; Sitz der Gesellschaft: München; Registergericht München, HRB 106955