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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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