Analysis with gcov while running the stress-ng urandom stressor shows that there are a couple of fortify panic paths that are highly unlikely to be executed for well-behaving code. Adding appropriate branch hints improves the stress-ng urandom stressor my a small but statistically measureable amount. Ran 100 x 1 minute tests and measured the stressor bogo-op rates on a Debian based Intel(R) Core(TM) Ultra 9 285K with a 6.15 kernel with turbo disabled to reduce jitter. Results based on a Geometic Mean of 100 tests: Without patch: 50512.95 bogo-ops/sec With patch: 50819.58 bogo-ops/sec %Std.Deviation of ~0.18%, so low jitter in results, improvement of ~0.6% Signed-off-by: Colin Ian King <colin.i.king@xxxxxxxxx> --- include/linux/fortify-string.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index e4ce1cae03bf..2ab8cb641d70 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -593,9 +593,9 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, * (The SIZE_MAX test is to optimize away checks where the buffer * lengths are unknown.) */ - if (p_size != SIZE_MAX && p_size < size) + if (unlikely(p_size != SIZE_MAX && p_size < size)) fortify_panic(func, FORTIFY_WRITE, p_size, size, true); - else if (q_size != SIZE_MAX && q_size < size) + else if (unlikely(q_size != SIZE_MAX && q_size < size)) fortify_panic(func, FORTIFY_READ, p_size, size, true); /* -- 2.50.0
