csky: mmu: Prevent spurious page faults
Commit Message
From: Guo Ren <guoren@linux.alibaba.com>
C-SKY MMU would pre-fetch invalid pte entries, and it could work with
flush_tlb_fix_spurious_fault, but the additional page fault exceptions
would reduce performance. So flushing the entry of the TLB would prevent
the following spurious page faults. Here is the test code:
define DATA_LEN 4096
define COPY_NUM (504*100)
unsigned char src[DATA_LEN*COPY_NUM] = {0};
unsigned char dst[DATA_LEN*COPY_NUM] = {0};
unsigned char func_src[DATA_LEN*COPY_NUM] = {0};
unsigned char func_dst[DATA_LEN*COPY_NUM] = {0};
void main(void)
{
int j;
for (j = 0; j < COPY_NUM; j++)
memcpy(&dst[j*DATA_LEN], &src[j*DATA_LEN], 4);
}
perf stat -e page-faults ./main.elf
The amount of page fault traps would be reduced in half with the patch.
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
---
arch/csky/abiv1/cacheflush.c | 2 ++
arch/csky/abiv2/cacheflush.c | 2 ++
2 files changed, 4 insertions(+)
@@ -40,6 +40,8 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn = pte_pfn(*ptep);
struct page *page;
+ flush_tlb_page(vma, addr);
+
if (!pfn_valid(pfn))
return;
@@ -12,6 +12,8 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
unsigned long addr;
struct page *page;
+ flush_tlb_page(vma, address);
+
if (!pfn_valid(pte_pfn(*pte)))
return;