Messages in this thread | | | Date | Thu, 22 Aug 2019 03:46:42 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH v3 1/3] RISC-V: Issue a local tlbflush if possible. |
| |
On Wed, Aug 21, 2019 at 05:46:42PM -0700, Atish Patra wrote: > In RISC-V, tlb flush happens via SBI which is expensive. If the local > cpu is the only cpu in cpumask, there is no need to invoke a SBI call. > > Just do a local flush and return. > > Signed-off-by: Atish Patra <atish.patra@wdc.com> > --- > arch/riscv/mm/tlbflush.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c > index df93b26f1b9d..36430ee3bed9 100644 > --- a/arch/riscv/mm/tlbflush.c > +++ b/arch/riscv/mm/tlbflush.c > @@ -2,6 +2,7 @@ > > #include <linux/mm.h> > #include <linux/smp.h> > +#include <linux/sched.h> > #include <asm/sbi.h> > > void flush_tlb_all(void) > @@ -13,9 +14,23 @@ static void __sbi_tlb_flush_range(struct cpumask *cmask, unsigned long start, > unsigned long size) > { > struct cpumask hmask; > + unsigned int cpuid = get_cpu(); > > + if (!cmask) { > + riscv_cpuid_to_hartid_mask(cpu_online_mask, &hmask); > + goto issue_sfence; > + } > + > + if (cpumask_test_cpu(cpuid, cmask) && cpumask_weight(cmask) == 1) { > + local_flush_tlb_all(); > + goto done; > + }
I think a single core on a SMP kernel is a valid enough use case given how litte distros still have UP kernels. So Maybe this shiuld rather be:
if (!cmask) cmask = cpu_online_mask;
if (cpumask_test_cpu(cpuid, cmask) && cpumask_weight(cmask) == 1) { local_flush_tlb_all(); } else { riscv_cpuid_to_hartid_mask(cmask, &hmask); sbi_remote_sfence_vma(hmask.bits, start, size); }
| |