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powerpc/64s/radix: do not flush TLB on spurious fault 

In the case of a spurious fault (which can happen due to a race with
another thread that changes the page table), the default Linux mm code
calls flush_tlb_page for that address. This is not required because
the pte will be re-fetched. Hash does not wire this up to a hardware
TLB flush for this reason. This patch avoids the flush for radix.

>From Power ISA v3.0B, p.1090:

    Setting a Reference or Change Bit or Upgrading Access Authority
    (PTE Subject to Atomic Hardware Updates)

    If the only change being made to a valid PTE that is subject to
    atomic hardware updates is to set the Refer- ence or Change bit to
    1 or to add access authorities, a simpler sequence suffices
    because the translation hardware will refetch the PTE if an access
    is attempted for which the only problems were reference and/or
    change bits needing to be set or insufficient access authority.

The nest MMU on POWER9 does not re-fetch the PTE after such an access
attempt before faulting, so address spaces with a coprocessor
attached will continue to flush in these cases.

This reduces tlbies for a kernel compile workload from 0.95M to 0.90M.

fork --fork --exec benchmark improved 0.5% (12300->12400).

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2018-06-01 20:01:16 +10:00 committed by Michael Ellerman
parent e5f7cb58c2
commit 6d8278c414
1 changed files with 11 additions and 1 deletions
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12
arch/powerpc/include/asm/book3s/64/tlbflush.h
View File

@ -4,7 +4,7 @@
#define MMU_NO_CONTEXT ~0UL #define MMU_NO_CONTEXT ~0UL
#include <linux/mm_types.h>
#include <asm/book3s/64/tlbflush-hash.h> #include <asm/book3s/64/tlbflush-hash.h>
#include <asm/book3s/64/tlbflush-radix.h> #include <asm/book3s/64/tlbflush-radix.h>
@ -137,6 +137,16 @@ static inline void flush_all_mm(struct mm_struct *mm)
#define flush_tlb_page(vma, addr) local_flush_tlb_page(vma, addr) #define flush_tlb_page(vma, addr) local_flush_tlb_page(vma, addr)
#define flush_all_mm(mm) local_flush_all_mm(mm) #define flush_all_mm(mm) local_flush_all_mm(mm)
#endif /* CONFIG_SMP */ #endif /* CONFIG_SMP */
#define flush_tlb_fix_spurious_fault flush_tlb_fix_spurious_fault
static inline void flush_tlb_fix_spurious_fault(struct vm_area_struct *vma,
unsigned long address)
{
/* See ptep_set_access_flags comment */
if (atomic_read(&vma->vm_mm->context.copros) > 0)
flush_tlb_page(vma, address);
}
/* /*
* flush the page walk cache for the address * flush the page walk cache for the address
*/ */