From: Tobias Burnus <tobias@codesourcery.com>
To: Andrew Stubbs <ams@codesourcery.com>,
Jakub Jelinek <jakub@redhat.com>,
Thomas Schwinge <thomas@codesourcery.com>
Cc: <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH 02/17] libgomp: pinned memory
Date: Thu, 8 Dec 2022 16:02:11 +0100 [thread overview]
Message-ID: <265e852f-e31f-015a-1a3e-c6468f404c9b@codesourcery.com> (raw)
In-Reply-To: <ee1df1d3-3dfb-8b4f-f9d8-11b43b4eb304@codesourcery.com>
On 08.12.22 15:35, Andrew Stubbs wrote:
> On 08/12/2022 14:02, Tobias Burnus wrote:
>> With available, I assume that nvptx is an 'available device' (per OpenMP
>> definition, finally added in TR11), i.e. there is an image for nvptx and
>> - after omp_requires filtering - there remains at least one nvptx
>> device.
>
> If plugin-nvptx has been loaded then the function will be available.
> Do we need to get fancier than that?
I think it does not really make sense to use CUDA if there is no single device.
In terms of loading, the code does:
gomp_target_init(void)
{
...
cur = OFFLOAD_PLUGINS; /* This is a comma-separated string with the supported plugins. */
...
if (gomp_load_plugin_for_device (¤t_device, plugin_name))
{
int omp_req = omp_requires_mask & ~GOMP_REQUIRES_TARGET_USED;
new_num_devs = current_device.get_num_devices_func (omp_req);
Thus, CUDA is loaded at the 'gomp_load_plugin_for_device' line and at the
'new_num_devs =' line, it has been filtered for OpenMP's 'requires' demands.*
Thus, 'new_num_devs' contains the number of 'accessible devices' (OpenMP definition),
filtered for the 'requires'* (which part of the 'supported devices' requirements).
(* With some caveats related to late loading of offloading code from (shared) libraries.)
* * *
Admittedly, this does not yet cover the last suggested feature:
GOMP_offload_register_ver (...)
{
gomp_load_image_to_device (devicep, version,
which is relevant for the first part of:
'supported devices' - '... supported by the implementation for execution of target code ...
requires directive are fulfilled'.
(available = (intersection of 'accessible devices' and 'supported devices') possibly
filtered + reordered via the OMP_AVAILABLE_DEVICES env var.)
I am not sure how strictly it is required and when we know when the all offload_register are
over; I do note that OpenMP TR 11 has an over-engineered OMP_AVAILABLE_DEVICES environment
variable which permits to filter the list of available devices – which also requires early
access to the initial 'available devices' list. But it might be sufficient to rely on the
device-is-accessible + requires filtering and ignore whether an actual image is available.
Tobias
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next prev parent reply other threads:[~2022-12-08 15:02 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-07 10:34 [PATCH 00/17] openmp, nvptx, amdgcn: 5.0 Memory Allocators Andrew Stubbs
2022-07-07 10:34 ` [PATCH 01/17] libgomp, nvptx: low-latency memory allocator Andrew Stubbs
2022-12-08 11:40 ` Jakub Jelinek
2022-07-07 10:34 ` [PATCH 02/17] libgomp: pinned memory Andrew Stubbs
2022-12-08 12:11 ` Jakub Jelinek
2022-12-08 12:51 ` Andrew Stubbs
2022-12-08 14:02 ` Tobias Burnus
2022-12-08 14:35 ` Andrew Stubbs
2022-12-08 15:02 ` Tobias Burnus [this message]
2022-07-07 10:34 ` [PATCH 03/17] libgomp, openmp: Add ompx_pinned_mem_alloc Andrew Stubbs
2022-07-07 10:34 ` [PATCH 04/17] openmp, nvptx: low-lat memory access traits Andrew Stubbs
2022-07-07 10:34 ` [PATCH 05/17] openmp, nvptx: ompx_unified_shared_mem_alloc Andrew Stubbs
2022-07-07 10:34 ` [PATCH 06/17] openmp: Add -foffload-memory Andrew Stubbs
2022-07-07 10:34 ` [PATCH 07/17] openmp: allow requires unified_shared_memory Andrew Stubbs
2022-07-07 10:34 ` [PATCH 08/17] openmp: -foffload-memory=pinned Andrew Stubbs
2022-07-07 11:54 ` Tobias Burnus
2022-07-07 22:18 ` Andrew Stubbs
2022-07-08 9:00 ` Tobias Burnus
2022-07-08 9:55 ` Andrew Stubbs
2022-07-08 9:57 ` Tobias Burnus
2023-02-20 14:59 ` Prototype 'GOMP_enable_pinned_mode' (was: [PATCH 08/17] openmp: -foffload-memory=pinned) Thomas Schwinge
2022-07-07 10:34 ` [PATCH 09/17] openmp: Use libgomp memory allocation functions with unified shared memory Andrew Stubbs
2022-07-07 10:34 ` [PATCH 10/17] Add parsing support for allocate directive (OpenMP 5.0) Andrew Stubbs
2022-07-07 10:34 ` [PATCH 11/17] Translate " Andrew Stubbs
2022-07-07 10:34 ` [PATCH 12/17] Handle cleanup of omp allocated variables " Andrew Stubbs
2022-07-07 10:34 ` [PATCH 13/17] Gimplify allocate directive " Andrew Stubbs
2022-07-07 10:34 ` [PATCH 14/17] Lower " Andrew Stubbs
2022-07-07 10:34 ` [PATCH 15/17] amdgcn: Support XNACK mode Andrew Stubbs
2022-07-07 10:34 ` [PATCH 16/17] amdgcn, openmp: Auto-detect USM mode and set HSA_XNACK Andrew Stubbs
2022-07-07 10:34 ` [PATCH 17/17] amdgcn: libgomp plugin USM implementation Andrew Stubbs
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