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SubjectRe: [PATCH v3 3/3] RISC-V: Do not invoke SBI call if cpumask is empty
On Wed, Aug 21, 2019 at 05:46:44PM -0700, Atish Patra wrote:
> SBI calls are expensive. If cpumask is empty, there is no need to
> trap via SBI as no remote tlb flushing is required.
>
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> ---
> arch/riscv/mm/tlbflush.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> index 9f58b3790baa..2bd3c418d769 100644
> --- a/arch/riscv/mm/tlbflush.c
> +++ b/arch/riscv/mm/tlbflush.c
> @@ -21,6 +21,9 @@ static void __sbi_tlb_flush_range(struct cpumask *cmask, unsigned long start,
> goto issue_sfence;
> }
>
> + if (cpumask_empty(cmask))
> + goto done;

I think this can even be done before the get_cpu to optimize it a little
further.

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