[libc-commits] [libc] 65e766d - [libc] Honour LIBC_GPU_TEST_JOBS in lit test runs (#193797)

[via libc-commits]

Author: Jeff Bailey
Date: 2026-04-24T08:20:03+01:00
New Revision: 65e766dfda81c12a26750adc21bec7f13166a42f

URL: https://github.com/llvm/llvm-project/commit/65e766dfda81c12a26750adc21bec7f13166a42f
DIFF: https://github.com/llvm/llvm-project/commit/65e766dfda81c12a26750adc21bec7f13166a42f.diff

LOG: [libc] Honour LIBC_GPU_TEST_JOBS in lit test runs (#193797)

Under CTest, LIBC_GPU_TEST_JOBS controlled a ninja job pool that limited
concurrent GPU test processes. The AMD GPU buildbot sets this to 4 to
avoid overloading the GPU driver.

When running tests via lit, this constraint was lost because lit uses
its own -j flag (defaulting to nproc, or set to 64 on the AMD bot via
LLVM_LIT_ARGS). All GPU loader processes launched simultaneously,
leading to hangs from GPU resource exhaustion.

Propagated LIBC_GPU_TEST_JOBS into the lit site config as a parallelism
group so lit throttles GPU test concurrency independently of the global
-j setting.

Added: 
    

Modified: 
    libc/cmake/modules/prepare_libc_gpu_build.cmake
    libc/test/lit.site.cfg.py.in

Removed: 
    


################################################################################
diff  --git a/libc/cmake/modules/prepare_libc_gpu_build.cmake b/libc/cmake/modules/prepare_libc_gpu_build.cmake
index c87a1df926c85..554c6c49b0435 100644
--- a/libc/cmake/modules/prepare_libc_gpu_build.cmake
+++ b/libc/cmake/modules/prepare_libc_gpu_build.cmake
@@ -29,6 +29,7 @@ if(LIBC_GPU_TEST_JOBS)
   set_property(GLOBAL PROPERTY JOB_POOLS LIBC_GPU_TEST_POOL=${LIBC_GPU_TEST_JOBS})
   set(LIBC_HERMETIC_TEST_JOB_POOL JOB_POOL LIBC_GPU_TEST_POOL)
 else()
+  set(LIBC_GPU_TEST_JOBS 1)
   set_property(GLOBAL PROPERTY JOB_POOLS LIBC_GPU_TEST_POOL=1)
   set(LIBC_HERMETIC_TEST_JOB_POOL JOB_POOL LIBC_GPU_TEST_POOL)
 endif()

diff  --git a/libc/test/lit.site.cfg.py.in b/libc/test/lit.site.cfg.py.in
index 3668a491cd05c..bc8d0e3e31713 100644
--- a/libc/test/lit.site.cfg.py.in
+++ b/libc/test/lit.site.cfg.py.in
@@ -40,3 +40,8 @@ if hasattr(config, "llvm_tools_dir") and config.llvm_tools_dir:
         [config.llvm_tools_dir, config.environment.get("PATH", "")]
     )
 
+# Limit concurrent GPU tests to avoid overloading the GPU driver.
+libc_gpu_test_jobs = "@LIBC_GPU_TEST_JOBS@"
+if libc_gpu_test_jobs:
+    lit_config.parallelism_groups["libc-gpu"] = int(libc_gpu_test_jobs)
+    config.parallelism_group = "libc-gpu"