scripts/pahole-flags.sh: Parse DWARF and generate BTF with multithreading.

Pass a "-j" argument to pahole if possible to reduce the time of
generating BTF info.

Since v1.22, pahole can parse DWARF and generate BTF with
multithreading to speed up the conversion.  It will reduce the overall
build time of the kernel for seconds.

v3 fixes whitespaces and improves the commit description.
v2 checks the version of pahole to enable multithreading only if possible.

[v2] https://lore.kernel.org/bpf/20220216193431.2691015-1-kuifeng@fb.com/
[v1] https://lore.kernel.org/bpf/20220216004616.2079689-1-kuifeng@fb.com/

Signed-off-by: Kui-Feng Lee <kuifeng@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220217175427.649713-1-kuifeng@fb.com

diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh
index c293941612e72216eff29dc1aaa17e9fad6d8a38..0d99ef17e4a52876a895295b16320646344ad0e8 100755 (executable)
--- a/scripts/pahole-flags.sh
+++ b/scripts/pahole-flags.sh
@@ -16,5 +16,8 @@ fi
 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"
+fi
 
 echo ${extra_paholeopt}