From 47a00e599b5f334815b95c4f8a703f6133b28767 Mon Sep 17 00:00:00 2001 From: Giuliano Procida Date: Thu, 23 May 2024 09:47:16 +0100 Subject: [PATCH] ANDROID: pahole -J -j1 for reproducible BTF Versions of pahole from 1.22 support multi-threaded operation with separate CUs being processed independently. This results in non-deterministic and effectively non-reproducible output for kernel objects. Later versions of pahole aim to support determinism by retiring CUs in order. We regain determinism by restricting parallelism to 1 at the cost of some performance. The default parallelism of `pahole -J` is the number of online processors * 1.1. Experiments on a workstation with 36 cores reveal that performance is actually worse for `vmlinux` at `-j` (8.9s) than at `-j3` (7.8s) and the optimum is around `-j9` (4.9s). No parallelism is slowest (18.8s), but still acceptable for GKI. Bug: 342094847 Change-Id: Ibd72ac638faa1826f6655b336cc7001591ea70f1 Signed-off-by: Giuliano Procida --- scripts/pahole-flags.sh | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh index 728d55190d97..746e91c86860 100755 --- a/scripts/pahole-flags.sh +++ b/scripts/pahole-flags.sh @@ -17,7 +17,7 @@ if [ "${pahole_ver}" -ge "121" ]; then extra_paholeopt="${extra_paholeopt} --btf_gen_floats" fi if [ "${pahole_ver}" -ge "122" ]; then - extra_paholeopt="${extra_paholeopt} -j" + extra_paholeopt="${extra_paholeopt} -j1" fi if [ "${pahole_ver}" -ge "124" ]; then # see PAHOLE_HAS_LANG_EXCLUDE