linux-kernel - [PATCH 1/1] arm/syscalls: mark syscall invocation as likely in invoke

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Message-Id: <20250919100042.497861-1-pengcan@kylinos.cn>
Date: Fri, 19 Sep 2025 18:00:42 +0800
From: Can Peng <pengcan@...inos.cn>
To: catalin.marinas@....com,
	will@...nel.org
Cc: linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Can Peng <pengcan@...inos.cn>
Subject: [PATCH 1/1] arm/syscalls: mark syscall invocation as likely in invoke_syscall

The invoke_syscall() function is overwhelmingly called for
valid system call entries. Annotate the main path with likely()
to help the compiler generate better branch prediction hints,
reducing CPU pipeline stalls due to mispredictions.

This is a micro-optimization targeting syscall-heavy workloads.

Signed-off-by: Can Peng <pengcan@...inos.cn>
---
 arch/arm64/kernel/syscall.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index c442fcec6b9e..aba7ca6bca2d 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -43,7 +43,7 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 
 	add_random_kstack_offset();
 
-	if (scno < sc_nr) {
+	if (likely(scno < sc_nr)) {
 		syscall_fn_t syscall_fn;
 		syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)];
 		ret = __invoke_syscall(regs, syscall_fn);
-- 
2.25.1