From d1c735d44c12544cea9b04ca88d65c12892c0539 Mon Sep 17 00:00:00 2001 From: Colin Ian King Date: Thu, 13 Feb 2025 16:39:16 +0000 Subject: [PATCH] kcmp: improve performance adding an unlikely hint to task comparisons Adding an unlikely() hint on task comparisons on an unlikely error return path improves run-time performance of the kcmp system call. Benchmarking on an i9-12900 shows an improvement of ~5.5% on kcmp(). Results based on running 20 tests with turbo disabled (to reduce clock freq turbo changes), with 10 second run per test and comparing the number of kcmp calls per second. The % Standard deviation of 20 tests was ~0.25%, results are reliable. Signed-off-by: Colin Ian King Link: https://lore.kernel.org/r/20250213163916.709392-1-colin.i.king@gmail.com Signed-off-by: Christian Brauner --- kernel/kcmp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/kcmp.c b/kernel/kcmp.c index 2c596851f8a90..7c1a65bd5f8d3 100644 --- a/kernel/kcmp.c +++ b/kernel/kcmp.c @@ -145,7 +145,7 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type, */ task1 = find_task_by_vpid(pid1); task2 = find_task_by_vpid(pid2); - if (!task1 || !task2) + if (unlikely(!task1 || !task2)) goto err_no_task; get_task_struct(task1); -- 2.50.1