[v4,1/3] RISC-V: Do not invoke SBI call if cpumask is empty

Commit Message

Atish Patra Aug. 22, 2019, 7:51 a.m. UTC

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 <[e-mail]>
---
 arch/riscv/mm/tlbflush.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Christoph Hellwig Aug. 22, 2019, 8:10 a.m. UTC | #1

On Thu, Aug 22, 2019 at 12:51:49AM -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 <[e-mail]>

Looks good,

Reviewed-by: Christoph Hellwig <[e-mail]>

Patch

diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
index df93b26f1b9d..1293b8017ee0 100644
--- a/arch/riscv/mm/tlbflush.c
+++ b/arch/riscv/mm/tlbflush.c
@@ -14,6 +14,9 @@  static void __sbi_tlb_flush_range(struct cpumask *cmask, unsigned long start,
 {
 	struct cpumask hmask;
 
+	if (cpumask_empty(cmask))
+		return;
+
 	riscv_cpuid_to_hartid_mask(cmask, &hmask);
 	sbi_remote_sfence_vma(hmask.bits, start, size);
 }