Re: [PATCH v3 1/3] libgomp, nvptx: low-latency memory allocator
On 05.12.23 16:39, Andrew Stubbs wrote:
Hence, mentioning in this section in addition that
omp_low_lat_mem_space is honored on devices
seems to be the better location.
How about this?
LGTM – Thanks!
Tobias
--- a/libgomp/libgomp.texi
+++ b/libgomp/libgomp.texi
@@ -3012,9 +3012,9 @@ value.
@item omp_const_mem_alloc @tab omp_const_mem_space
@item omp_high_bw_mem_alloc @tab omp_high_bw_mem_space
@item omp_low_lat_mem_alloc @tab omp_low_lat_mem_space
-@item omp_cgroup_mem_alloc @tab --
-@item omp_pteam_mem_alloc @tab --
-@item omp_thread_mem_alloc @tab --
+@item omp_cgroup_mem_alloc @tab omp_low_lat_mem_space
(implementation defined)
+@item omp_pteam_mem_alloc @tab omp_low_lat_mem_space
(implementation defined)
+@item omp_thread_mem_alloc @tab omp_low_lat_mem_space
(implementation defined)
@end multitable
The predefined allocators use the default values for the traits,
@@ -3060,7 +3060,7 @@
OMP_ALLOCATOR=omp_low_lat_mem_space:pinned=true,partition=nearest
@item @emph{See also}:
@ref{Memory allocation}, @ref{omp_get_default_allocator},
-@ref{omp_set_default_allocator}
+@ref{omp_set_default_allocator}, @ref{Offload-Target Specific}
@item @emph{Reference}:
@uref{https://www.openmp.org/, OpenMP specification v5.0}, Section 6.21
@@ -5710,7 +5710,8 @@ For the memory spaces, the following applies:
@itemize
@item @code{omp_default_mem_space} is supported
@item @code{omp_const_mem_space} maps to @code{omp_default_mem_space}
-@item @code{omp_low_lat_mem_space} maps to @code{omp_default_mem_space}
+@item @code{omp_low_lat_mem_space} is only available on supported
devices,
+ and maps to @code{omp_default_mem_space} otherwise.
@item @code{omp_large_cap_mem_space} maps to
@code{omp_default_mem_space},
unless the memkind library is available
@item @code{omp_high_bw_mem_space} maps to @code{omp_default_mem_space},
@@ -5766,6 +5767,9 @@ Additional notes regarding the traits:
@item The @code{sync_hint} trait has no effect.
@end itemize
+See also:
+@ref{Offload-Target Specifics}
+
-
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Re: [PATCH v3 1/3] libgomp, nvptx: low-latency memory allocator
On 04/12/2023 16:04, Tobias Burnus wrote:
On 03.12.23 01:32, Andrew Stubbs wrote:
This patch adds support for allocating low-latency ".shared" memory on
NVPTX GPU device, via the omp_low_lat_mem_space and omp_alloc. The
memory
can be allocated, reallocated, and freed using a basic but fast
algorithm,
is thread safe and the size of the low-latency heap can be configured
using
the GOMP_NVPTX_LOWLAT_POOL environment variable.
The use of the PTX dynamic_smem_size feature means that low-latency
allocator
will not work with the PTX 3.1 multilib.
For now, the omp_low_lat_mem_alloc allocator also works, but that will
change
when I implement the access traits.
...
LGTM, however, I about the following:
diff --git a/libgomp/libgomp.texi b/libgomp/libgomp.texi
index e5fe7af76af..39d0749e7b3 100644
--- a/libgomp/libgomp.texi
+++ b/libgomp/libgomp.texi
@@ -3012,11 +3012,14 @@ value.
@item omp_const_mem_alloc @tab omp_const_mem_space
@item omp_high_bw_mem_alloc @tab omp_high_bw_mem_space
@item omp_low_lat_mem_alloc @tab omp_low_lat_mem_space
-@item omp_cgroup_mem_alloc @tab --
-@item omp_pteam_mem_alloc @tab --
-@item omp_thread_mem_alloc @tab --
+@item omp_cgroup_mem_alloc @tab omp_low_lat_mem_space
(implementation defined)
+@item omp_pteam_mem_alloc @tab omp_low_lat_mem_space
(implementation defined)
+@item omp_thread_mem_alloc @tab omp_low_lat_mem_space
(implementation defined)
@end multitable
+The @code{omp_low_lat_mem_space} is only available on supported devices.
+See @ref{Offload-Target Specifics}.
+
Whether it would be clearer to have this wording not here for the
OMP_ALLOCATOR env, i.e.
https://gcc.gnu.org/onlinedocs/libgomp/OMP_005fALLOCATOR.html
but just a simple crossref like:
--- a/libgomp/libgomp.texi
+++ b/libgomp/libgomp.texi
@@ -3061,5 +3061,5 @@
OMP_ALLOCATOR=omp_low_lat_mem_space:pinned=true,partition=nearest
@item @emph{See also}:
@ref{Memory allocation}, @ref{omp_get_default_allocator},
-@ref{omp_set_default_allocator}
+@ref{omp_set_default_allocator}, @ref{Offload-Target Specifics}
@item @emph{Reference}:
And add your wording to:
https://gcc.gnu.org/onlinedocs/libgomp/Memory-allocation.html
As this sections mentions that "omp_low_lat_mem_space maps to
omp_default_mem_space" in general.
Hence, mentioning in this section in addition that
omp_low_lat_mem_space is honored on devices
seems to be the better location.
How about this?
--- a/libgomp/libgomp.texi
+++ b/libgomp/libgomp.texi
@@ -3012,9 +3012,9 @@ value.
@item omp_const_mem_alloc @tab omp_const_mem_space
@item omp_high_bw_mem_alloc @tab omp_high_bw_mem_space
@item omp_low_lat_mem_alloc @tab omp_low_lat_mem_space
-@item omp_cgroup_mem_alloc @tab --
-@item omp_pteam_mem_alloc @tab --
-@item omp_thread_mem_alloc @tab --
+@item omp_cgroup_mem_alloc @tab omp_low_lat_mem_space
(implementation defined)
+@item omp_pteam_mem_alloc @tab omp_low_lat_mem_space
(implementation defined)
+@item omp_thread_mem_alloc @tab omp_low_lat_mem_space
(implementation defined)
@end multitable
The predefined allocators use the default values for the traits,
@@ -3060,7 +3060,7 @@
OMP_ALLOCATOR=omp_low_lat_mem_space:pinned=true,partition=nearest
@item @emph{See also}:
@ref{Memory allocation}, @ref{omp_get_default_allocator},
-@ref{omp_set_default_allocator}
+@ref{omp_set_default_allocator}, @ref{Offload-Target Specific}
@item @emph{Reference}:
@uref{https://www.openmp.org, OpenMP specification v5.0}, Section 6.21
@@ -5710,7 +5710,8 @@ For the memory spaces, the following applies:
@itemize
@item @code{omp_default_mem_space} is supported
@item @code{omp_const_mem_space} maps to @code{omp_default_mem_space}
-@item @code{omp_low_lat_mem_space} maps to @code{omp_default_mem_space}
+@item @code{omp_low_lat_mem_space} is only available on supported devices,
+ and maps to @code{omp_default_mem_space} otherwise.
@item @code{omp_large_cap_mem_space} maps to @code{omp_default_mem_space},
unless the memkind library is available
@item @code{omp_high_bw_mem_space} maps to @code{omp_default_mem_space},
@@ -5766,6 +5767,9 @@ Additional notes regarding the traits:
@item The @code{sync_hint} trait has no effect.
@end itemize
+See also:
+@ref{Offload-Target Specifics}
+
@c -
@c Offload-Target Specifics
@c -
Tobias
-
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Re: [PATCH v3 1/3] libgomp, nvptx: low-latency memory allocator
Hi Andrew,
I now looked at the whole series - and the series LGTM,
except for some testcase issues, as outlined below.
First, I notice that there is no call to:
omp_destroy_allocator (gpu_lowlat);
While it might make sense to leave some of the testcases
without that call for testing purpose, I think at least one
it not all (but one?) should call it for completeness/testing
purpose.
However, the real issue is:
On 03.12.23 01:32, Andrew Stubbs wrote:
* testsuite/libgomp.c/omp_alloc-4.c: New test.
* testsuite/libgomp.c/omp_alloc-6.c: New test.
In particular: If you run this without offloading
(not configured, -foffload=disable, or no hardware available)
Result: This will fail all over the place.
I am not sure whether some tests should remain with hostfallback.
If yes, I think you need a check whether
omp_get_initial_device() == omp_get_default_device()
or something similar.
If not, you should expect it to fail unless
{ target offload_device }
In any case, I get with host fallback the following for the -4.c test:
62: allocate did not coalesce first two chunks
66: allocate did not split first chunk (1)
68: allocate did not split first chunk (2)
73: allocate did not coalesce middle two chunks
77: allocate did not split second chunk (1)
79: allocate did not split second chunk (2)
84: allocate did not coalesce first two chunks, reverse free
95: allocate did not coalesce second two chunks, reverse free
107: allocate did not coalesce first three chunks
111: allocate did not split first chunk (1)
115: allocate did not split first chunk (3)
121: allocate did not coalesce last three chunks
125: allocate did not split second chunk (1)
129: allocate did not split second chunk (3)
135: allocate did not coalesce first three chunks, reverse free
149: allocate did not coalesce second three chunks, reverse free
163: allocate did not coalesce first three chunks, mixed free
167: allocate did not split first chunk (1), mixed free
169: allocate did not split first chunk (2), mixed free
177: allocate did not coalesce second three chunks, mixed free
181: allocate did not split second chunk (1), mixed free
183: allocate did not split second chunk (2), mixed free
192: allocate did not coalesce all memory
And with ASAN already for:
49: allocate did not reuse first chunk
53: allocate did not reuse second chunk
57: allocate did not reuse third chunk
AddressSanitizer:DEADLYSIGNAL
=
==1395708==ERROR: AddressSanitizer: SEGV on unknown address 0xfffb
(pc 0x7ffa2f649025 bp 0xfffb sp 0x7ffe22a90910 T0)
...
#4 0x401748 in main._omp_fn.0 libgomp/testsuite/libgomp.c/omp_alloc-4.c:59
And the -6 tests fails with:
72: realloc did not extend into whole next chunk
free(): invalid pointer
Segmentation fault (core dumped)
where the free() crash is at:
74 p = omp_realloc (b, size3, lowlat, lowlat);
And with ASAN it fails already with:
48: realloc did not reuse same size chunk, no space after
=
==1396453==ERROR: AddressSanitizer: heap-use-after-free on address
0x504000b0 at pc 0x7f83c3ef9406 bp 0x7fffc48d7e10 sp 0x7fffc48d75d0
...
READ of size 8 at 0x504000b0 thread T0
...
#5 0x401358 in main libgomp/testsuite/libgomp.c/omp_alloc-6.c:23
freed by thread T0 here:
#1 0x7f83c459af6a in omp_realloc
../../../repos/gcc/libgomp/config/linux/../../allocator.c:1219
previously allocated by thread T0 here:
#1 0x7f83c459a13b in omp_aligned_alloc
../../../repos/gcc/libgomp/config/linux/../../allocator.c:626
Tobias
-
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Re: [PATCH v3 1/3] libgomp, nvptx: low-latency memory allocator
On 03.12.23 01:32, Andrew Stubbs wrote:
This patch adds support for allocating low-latency ".shared" memory on
NVPTX GPU device, via the omp_low_lat_mem_space and omp_alloc. The memory
can be allocated, reallocated, and freed using a basic but fast algorithm,
is thread safe and the size of the low-latency heap can be configured using
the GOMP_NVPTX_LOWLAT_POOL environment variable.
The use of the PTX dynamic_smem_size feature means that low-latency allocator
will not work with the PTX 3.1 multilib.
For now, the omp_low_lat_mem_alloc allocator also works, but that will change
when I implement the access traits.
...
LGTM, however, I about the following:
diff --git a/libgomp/libgomp.texi b/libgomp/libgomp.texi
index e5fe7af76af..39d0749e7b3 100644
--- a/libgomp/libgomp.texi
+++ b/libgomp/libgomp.texi
@@ -3012,11 +3012,14 @@ value.
@item omp_const_mem_alloc @tab omp_const_mem_space
@item omp_high_bw_mem_alloc @tab omp_high_bw_mem_space
@item omp_low_lat_mem_alloc @tab omp_low_lat_mem_space
-@item omp_cgroup_mem_alloc @tab --
-@item omp_pteam_mem_alloc @tab --
-@item omp_thread_mem_alloc @tab --
+@item omp_cgroup_mem_alloc @tab omp_low_lat_mem_space (implementation
defined)
+@item omp_pteam_mem_alloc @tab omp_low_lat_mem_space (implementation
defined)
+@item omp_thread_mem_alloc @tab omp_low_lat_mem_space (implementation
defined)
@end multitable
+The @code{omp_low_lat_mem_space} is only available on supported devices.
+See @ref{Offload-Target Specifics}.
+
Whether it would be clearer to have this wording not here for the OMP_ALLOCATOR
env, i.e.
https://gcc.gnu.org/onlinedocs/libgomp/OMP_005fALLOCATOR.html
but just a simple crossref like:
--- a/libgomp/libgomp.texi
+++ b/libgomp/libgomp.texi
@@ -3061,5 +3061,5 @@
OMP_ALLOCATOR=omp_low_lat_mem_space:pinned=true,partition=nearest
@item @emph{See also}:
@ref{Memory allocation}, @ref{omp_get_default_allocator},
-@ref{omp_set_default_allocator}
+@ref{omp_set_default_allocator}, @ref{Offload-Target Specifics}
@item @emph{Reference}:
And add your wording to:
https://gcc.gnu.org/onlinedocs/libgomp/Memory-allocation.html
As this sections mentions that "omp_low_lat_mem_space maps to
omp_default_mem_space" in general.
Hence, mentioning in this section in addition that omp_low_lat_mem_space is
honored on devices
seems to be the better location.
Tobias
-
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
[PATCH v3 1/3] libgomp, nvptx: low-latency memory allocator
This patch adds support for allocating low-latency ".shared" memory on
NVPTX GPU device, via the omp_low_lat_mem_space and omp_alloc. The memory
can be allocated, reallocated, and freed using a basic but fast algorithm,
is thread safe and the size of the low-latency heap can be configured using
the GOMP_NVPTX_LOWLAT_POOL environment variable.
The use of the PTX dynamic_smem_size feature means that low-latency allocator
will not work with the PTX 3.1 multilib.
For now, the omp_low_lat_mem_alloc allocator also works, but that will change
when I implement the access traits.
libgomp/ChangeLog:
* allocator.c (MEMSPACE_ALLOC): New macro.
(MEMSPACE_CALLOC): New macro.
(MEMSPACE_REALLOC): New macro.
(MEMSPACE_FREE): New macro.
(predefined_alloc_mapping): New array. Add _Static_assert to match.
(ARRAY_SIZE): New macro.
(omp_aligned_alloc): Use MEMSPACE_ALLOC.
Implement fall-backs for predefined allocators. Simplify existing
fall-backs.
(omp_free): Use MEMSPACE_FREE.
(omp_calloc): Use MEMSPACE_CALLOC. Implement fall-backs for
predefined allocators. Simplify existing fall-backs.
(omp_realloc): Use MEMSPACE_REALLOC, MEMSPACE_ALLOC, and MEMSPACE_FREE.
Implement fall-backs for predefined allocators. Simplify existing
fall-backs.
* config/nvptx/team.c (__nvptx_lowlat_pool): New asm variable.
(__nvptx_lowlat_init): New prototype.
(gomp_nvptx_main): Call __nvptx_lowlat_init.
* libgomp.texi: Update memory space table.
* plugin/plugin-nvptx.c (lowlat_pool_size): New variable.
(GOMP_OFFLOAD_init_device): Read the GOMP_NVPTX_LOWLAT_POOL envvar.
(GOMP_OFFLOAD_run): Apply lowlat_pool_size.
* basic-allocator.c: New file.
* config/nvptx/allocator.c: New file.
* testsuite/libgomp.c/omp_alloc-1.c: New test.
* testsuite/libgomp.c/omp_alloc-2.c: New test.
* testsuite/libgomp.c/omp_alloc-3.c: New test.
* testsuite/libgomp.c/omp_alloc-4.c: New test.
* testsuite/libgomp.c/omp_alloc-5.c: New test.
* testsuite/libgomp.c/omp_alloc-6.c: New test.
Co-authored-by: Kwok Cheung Yeung
Co-Authored-By: Thomas Schwinge
---
libgomp/allocator.c | 246 --
libgomp/basic-allocator.c | 380 ++
libgomp/config/nvptx/allocator.c | 120 +++
libgomp/config/nvptx/team.c | 18 +
libgomp/libgomp.texi | 9 +-
libgomp/plugin/plugin-nvptx.c | 23 +-
libgomp/testsuite/libgomp.c/omp_alloc-1.c | 56
libgomp/testsuite/libgomp.c/omp_alloc-2.c | 64
libgomp/testsuite/libgomp.c/omp_alloc-3.c | 42 +++
libgomp/testsuite/libgomp.c/omp_alloc-4.c | 196 +++
libgomp/testsuite/libgomp.c/omp_alloc-5.c | 63
libgomp/testsuite/libgomp.c/omp_alloc-6.c | 117 +++
12 files changed, 1231 insertions(+), 103 deletions(-)
create mode 100644 libgomp/basic-allocator.c
create mode 100644 libgomp/config/nvptx/allocator.c
create mode 100644 libgomp/testsuite/libgomp.c/omp_alloc-1.c
create mode 100644 libgomp/testsuite/libgomp.c/omp_alloc-2.c
create mode 100644 libgomp/testsuite/libgomp.c/omp_alloc-3.c
create mode 100644 libgomp/testsuite/libgomp.c/omp_alloc-4.c
create mode 100644 libgomp/testsuite/libgomp.c/omp_alloc-5.c
create mode 100644 libgomp/testsuite/libgomp.c/omp_alloc-6.c
diff --git a/libgomp/allocator.c b/libgomp/allocator.c
index b4e50e2ad72..fa398128368 100644
--- a/libgomp/allocator.c
+++ b/libgomp/allocator.c
@@ -37,6 +37,47 @@
#define omp_max_predefined_alloc omp_thread_mem_alloc
+/* These macros may be overridden in config//allocator.c.
+ The following definitions (ab)use comma operators to avoid unused
+ variable errors. */
+#ifndef MEMSPACE_ALLOC
+#define MEMSPACE_ALLOC(MEMSPACE, SIZE) \
+ malloc (((void)(MEMSPACE), (SIZE)))
+#endif
+#ifndef MEMSPACE_CALLOC
+#define MEMSPACE_CALLOC(MEMSPACE, SIZE) \
+ calloc (1, (((void)(MEMSPACE), (SIZE
+#endif
+#ifndef MEMSPACE_REALLOC
+#define MEMSPACE_REALLOC(MEMSPACE, ADDR, OLDSIZE, SIZE) \
+ realloc (ADDR, (((void)(MEMSPACE), (void)(OLDSIZE), (SIZE
+#endif
+#ifndef MEMSPACE_FREE
+#define MEMSPACE_FREE(MEMSPACE, ADDR, SIZE) \
+ free (((void)(MEMSPACE), (void)(SIZE), (ADDR)))
+#endif
+
+/* Map the predefined allocators to the correct memory space.
+ The index to this table is the omp_allocator_handle_t enum value.
+ When the user calls omp_alloc with a predefined allocator this
+ table determines what memory they get. */
+static const omp_memspace_handle_t predefined_alloc_mapping[] = {
+ omp_default_mem_space, /* omp_null_allocator doesn't actually use this. */
+ omp_default_mem_space, /* omp_default_mem_alloc. */
+ omp_large_cap_mem_space, /* omp_large_cap_mem_alloc. */
+ omp_const_mem_space, /* omp_const_mem_alloc. */
+ omp_high_bw_mem_space, /* omp_high_bw_mem_alloc. */
