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>
610 has vipt aliasing issue, so we need to finish the cache flush
apis mentioned in cachetlb.rst to avoid data corruption.
Here is the list of modified apis in the patch:
- flush_kernel_dcache_page (new add)
- flush_dcache_mmap_lock (new add)
- flush_dcache_mmap_unlock (new add)
- flush_kernel_vmap_range (new add)
- invalidate_kernel_vmap_range (new add)
- flush_anon_page (new add)
- flush_cache_range (new add)
- flush_cache_vmap (flush all)
- flush_cache_vunmap (flush all)
- flush_cache_mm (only dcache flush)
- flush_icache_page (just nop)
- copy_from_user_page (remove no need flush)
- copy_to_user_page (remove no need flush)
Change to V2:
- Fixup compile error with xa_lock*(&mapping->i_pages)
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@infradead.org>
We use defer cache flush mechanism to improve the performance of
610, but the implementation is wrong. We fix it up now and update
the mechanism:
- Zero page needn't be flushed.
- If page is file mapping & non-touched in user space, defer flush.
- If page is anon mapping or dirty file mapping, flush immediately.
- In update_mmu_cache finish the defer flush by flush_dcache_page().
For 610 we need take care the dcache aliasing issue:
- VIPT cache with 8K-bytes size per way in 4K page granularity.
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Arnd Bergmann <arnd@arndb.de>
