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kcmp: improve performance adding an unlikely hint to task comparisons

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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 <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20250213163916.709392-1-colin.i.king@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Colin Ian King
2025-02-13 16:39:16 +00:00
committed by Christian Brauner
parent 1479be6258
commit d1c735d44c
1 changed files with 1 additions and 1 deletions
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2
kernel/kcmp.c
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@@ -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);