Both, __dax_pmd_fault, and clear_pmem() were taking special steps to
clear memory a page at a time to take advantage of non-temporal
clear_page() implementations. However, x86_64 does not use
non-temporal instructions for clear_page(), and arch_clear_pmem() was
always incurring the cost of __arch_wb_cache_pmem().
Clean up the assumption that doing clear_pmem() a page at a time is more
performant.
Reported-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
arch/x86/include/asm/pmem.h | 7 +------
fs/dax.c | 4 +---
2 files changed, 2 insertions(+), 9 deletions(-)
diff --git a/arch/x86/include/asm/pmem.h b/arch/x86/include/asm/pmem.h
index d8ce3ec816ab..1544fabcd7f9 100644
--- a/arch/x86/include/asm/pmem.h
+++ b/arch/x86/include/asm/pmem.h
@@ -132,12 +132,7 @@ static inline void arch_clear_pmem(void __pmem *addr, size_t size)
{
void *vaddr = (void __force *)addr;
- /* TODO: implement the zeroing via non-temporal writes */
- if (size == PAGE_SIZE && ((unsigned long)vaddr & ~PAGE_MASK) == 0)
- clear_page(vaddr);
- else
- memset(vaddr, 0, size);
-
+ memset(vaddr, 0, size);
__arch_wb_cache_pmem(vaddr, size);
}
diff --git a/fs/dax.c b/fs/dax.c
index 43671b68220e..19492cc65a30 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -641,9 +641,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
goto fallback;
if (buffer_unwritten(&bh) || buffer_new(&bh)) {
- int i;
- for (i = 0; i < PTRS_PER_PMD; i++)
- clear_pmem(kaddr + i * PAGE_SIZE, PAGE_SIZE);
+ clear_pmem(kaddr, PMD_SIZE);
wmb_pmem();
count_vm_event(PGMAJFAULT);
mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
--
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