[og12] libgomp: Document OpenMP 'pinned' memory (was: [PATCH] libgomp, openmp: pinned memory)
Commit Message
Hi!
On 2023-03-27T09:27:31+0000, "Stubbs, Andrew" <andrew.stubbs@siemens.com> wrote:
>> -----Original Message-----
>> From: Thomas Schwinge <thomas@codesourcery.com>
>> Sent: 24 March 2023 15:50
>>
>> On 2022-01-04T15:32:17+0000, Andrew Stubbs <ams@codesourcery.com>
>> wrote:
>> > This patch implements the OpenMP pinned memory trait [...]
>>
>> I figure it may be helpful to document the current og12 state of affairs; does
>> the attached "libgomp: Document OpenMP 'pinned' memory" look good to
>> you?
>
> I don't really know what "allocated via the device" means?
Heh, you're right.
> I mean, I presume you mean "via CUDA", but I don't think this is obvious to the average reader.
> Maybe "allocation is optimized for the device" or some such thing?
As we're in sections that are documenting GCN vs. nvptx specifics, we
might indeed call out which exact interfaces we're using.
How's the updated "libgomp: Document OpenMP 'pinned' memory", see
attached?
Grüße
Thomas
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Comments
On 27/03/2023 12:26, Thomas Schwinge wrote:
> Hi!
>
> On 2023-03-27T09:27:31+0000, "Stubbs, Andrew" <andrew.stubbs@siemens.com> wrote:
>>> -----Original Message-----
>>> From: Thomas Schwinge <thomas@codesourcery.com>
>>> Sent: 24 March 2023 15:50
>>>
>>> On 2022-01-04T15:32:17+0000, Andrew Stubbs <ams@codesourcery.com>
>>> wrote:
>>>> This patch implements the OpenMP pinned memory trait [...]
>>>
>>> I figure it may be helpful to document the current og12 state of affairs; does
>>> the attached "libgomp: Document OpenMP 'pinned' memory" look good to
>>> you?
>>
>> I don't really know what "allocated via the device" means?
>
> Heh, you're right.
>
>> I mean, I presume you mean "via CUDA", but I don't think this is obvious to the average reader.
>> Maybe "allocation is optimized for the device" or some such thing?
>
> As we're in sections that are documenting GCN vs. nvptx specifics, we
> might indeed call out which exact interfaces we're using.
>
> How's the updated "libgomp: Document OpenMP 'pinned' memory", see
> attached?
LGTM, FWIW.
Andrew
From 03e09ad4e0b4cd2232e8bb036dd2562b18ea2686 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <thomas@codesourcery.com>
Date: Fri, 24 Mar 2023 15:14:57 +0100
Subject: [PATCH] libgomp: Document OpenMP 'pinned' memory
libgomp/
* libgomp.texi (AMD Radeon, nvptx): Document OpenMP 'pinned'
memory.
---
libgomp/libgomp.texi | 8 ++++++++
1 file changed, 8 insertions(+)
@@ -4456,6 +4456,9 @@ The implementation remark:
@item OpenMP code that has a requires directive with @code{unified_address} or
@code{unified_shared_memory} will remove any GCN device from the list of
available devices (``host fallback'').
+@item OpenMP @emph{pinned} memory (@code{omp_atk_pinned},
+ @code{ompx_pinned_mem_alloc}, for example)
+ is allocated via @code{mmap}, @code{mlock}.
@end itemize
@@ -4518,6 +4521,11 @@ The implementation remark:
@item OpenMP code that has a requires directive with @code{unified_address}
or @code{unified_shared_memory} will remove any nvptx device from the
list of available devices (``host fallback'').
+@item OpenMP @emph{pinned} memory (@code{omp_atk_pinned},
+ @code{ompx_pinned_mem_alloc}, for example)
+ is allocated via @code{cuMemHostAlloc} (CUDA Driver API).
+ This potentially helps optimization of host <-> device data
+ transfers.
@end itemize
--
2.25.1