Commit 1f62ed00 authored by Guo Ren's avatar Guo Ren
Browse files

csky: mmu: Prevent spurious page faults 



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: default avatarGuo Ren <guoren@linux.alibaba.com>
Signed-off-by: default avatarGuo Ren <guoren@kernel.org>
parent 74c53b57

arch/csky/abiv1/cacheflush.c

+3 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <asm/cache.h>

#include <asm/cacheflush.h>

#include <asm/cachectl.h>

#include <asm/tlbflush.h>



#define PG_dcache_clean		PG_arch_1
@@ -40,6 +41,8 @@ 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;

arch/csky/abiv2/cacheflush.c

+3 −0
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
#include <linux/highmem.h>

#include <linux/mm.h>

#include <asm/cache.h>

#include <asm/tlbflush.h>



void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,

		      pte_t *pte)
@@ -12,6 +13,8 @@ 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;