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csky: mmu: Prevent spurious page faults

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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>
This commit is contained in:
Guo Ren
2023-04-06 04:46:49 -04:00
parent 74c53b5717
commit 1f62ed00a5
2 changed files with 6 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
arch/csky/abiv1/cacheflush.c
View File

@@ -11,6 +11,7 @@
#include <asm/cache.h> #include <asm/cache.h>
#include <asm/cacheflush.h> #include <asm/cacheflush.h>
#include <asm/cachectl.h> #include <asm/cachectl.h>
#include <asm/tlbflush.h>
#define PG_dcache_clean PG_arch_1 #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); unsigned long pfn = pte_pfn(*ptep);
struct page *page; struct page *page;
flush_tlb_page(vma, addr);
if (!pfn_valid(pfn)) if (!pfn_valid(pfn))
return; return;

3
arch/csky/abiv2/cacheflush.c
View File

@@ -5,6 +5,7 @@
#include <linux/highmem.h> #include <linux/highmem.h>
#include <linux/mm.h> #include <linux/mm.h>
#include <asm/cache.h> #include <asm/cache.h>
#include <asm/tlbflush.h>
void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
pte_t *pte) pte_t *pte)
@@ -12,6 +13,8 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
unsigned long addr; unsigned long addr;
struct page *page; struct page *page;
flush_tlb_page(vma, address);
if (!pfn_valid(pte_pfn(*pte))) if (!pfn_valid(pte_pfn(*pte)))
return; return;