lkml.org 
[lkml]   [2019]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [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);
}

\
 
 \ /
  Last update: 2019-08-22 03:47    [W:0.168 / U:3.512 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site