From: Colin Ian King Date: Thu, 13 Feb 2025 16:39:16 +0000 (+0000) Subject: kcmp: improve performance adding an unlikely hint to task comparisons X-Git-Tag: v6.15-rc1~254^2~19 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d1c735d44c12544cea9b04ca88d65c12892c0539;p=thirdparty%2Fkernel%2Flinux.git 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 --- 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);