diff mbox series

[committed,OG10] amdgcn, openmp: Fix concurrency in low-latency allocator

Message ID c5a95ca2-d7e8-280d-1351-c9dfb5b26de3@codesourcery.com
State Unresolved
Headers
Series [committed,OG10] amdgcn, openmp: Fix concurrency in low-latency allocator |

Checks

Context Check Description
snail/gcc-patch-check warning Git am fail log

Commit Message

Andrew Stubbs April 20, 2023, 1:29 p.m. UTC 
  I've committed this to the devel/omp/gcc-12 branch.

The patch fixes a concurrency issue where the spin-locks didn't work 
well if many GPU threads tried to free low-latency memory all at once.

Adding a short sleep instruction is enough for the hardware thread to 
yield and allow another to proceed. The alloc routine already had this 
feature, so this just corrects an accidental omission.

This patch will get folded into the previous OG12 patch series when I 
repost it for mainline.

Andrew
amdgcn, openmp: Fix concurrency in low-latency allocator

The previous code works fine on Fiji and Vega 10 devices, but bogs down in The
spin locks on Vega 20 or newer.  Adding the sleep instructions fixes the
problem.

libgomp/ChangeLog:

	* basic-allocator.c (basic_alloc_free): Use BASIC_ALLOC_YIELD.
	(basic_alloc_realloc): Use BASIC_ALLOC_YIELD.
diff mbox series

Patch

diff --git a/libgomp/basic-allocator.c b/libgomp/basic-allocator.c
index b4b9e4ba13a..a61828e48a0 100644
--- a/libgomp/basic-allocator.c
+++ b/libgomp/basic-allocator.c
@@ -188,6 +188,7 @@  basic_alloc_free (char *heap, void *addr, size_t size)
 	  break;
 	}
       /* Spin.  */
+      BASIC_ALLOC_YIELD;
     }
   while (1);
 
@@ -267,6 +268,7 @@  basic_alloc_realloc (char *heap, void *addr, size_t oldsize,
 	  break;
 	}
       /* Spin.  */
+      BASIC_ALLOC_YIELD;
     }
   while (1);