linux-kernel - Re: [PATCH] arm64: add unlikely hint to MTE async fault check in el0_svc

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Message-ID: <aNEsDswLSpBkf-5S@willie-the-truck>
Date: Mon, 22 Sep 2025 11:59:26 +0100
From: Will Deacon <will@...nel.org>
To: Li Qiang <liqiang01@...inos.cn>
Cc: catalin.marinas@....com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: add unlikely hint to MTE async fault check in
 el0_svc_common

On Fri, Sep 19, 2025 at 11:33:27AM +0800, Li Qiang wrote:
> Add unlikely() hint to the _TIF_MTE_ASYNC_FAULT flag check in
> el0_svc_common() since asynchronous MTE faults are expected to be
> rare occurrences during normal system call execution.
> 
> This optimization helps the compiler to improve instruction caching
> and branch prediction for the common case where no asynchronous
> MTE faults are pending, while maintaining correct behavior for
> the exceptional case where such faults need to be handled prior
> to system call execution.
> 
> Signed-off-by: Li Qiang <liqiang01@...inos.cn>
> ---
>  arch/arm64/kernel/syscall.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Does this result in a measurable performance difference?

Will