>>> On 13.08.12 at 13:43, "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> On Thu, Aug 09, 2012 at 04:22:04PM +0100, Jan Beulich wrote:
>> >>> On 09.08.12 at 17:03, "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
>
> ...
>
>> > ---
>> > arch/x86/include/asm/page.h | 2 ++
>> > arch/x86/include/asm/string_32.h | 5 +++++
>> > arch/x86/include/asm/string_64.h | 5 +++++
>> > arch/x86/lib/Makefile | 1 +
>> > arch/x86/lib/clear_page_nocache_32.S | 30 ++++++++++++++++++++++++++++++
>> > arch/x86/lib/clear_page_nocache_64.S | 29 +++++++++++++++++++++++++++++
>>
>> Couldn't this more reasonably go into clear_page_{32,64}.S?
>
> We don't have clear_page_32.S.
Sure, but you're introducing a file anyway. Fold the new code into
the existing file for 64-bit, and create a new, similarly named one
for 32-bit.
>> >+ xorl %eax,%eax
>> >+ movl $4096/64,%ecx
>> >+ .p2align 4
>> >+.Lloop:
>> >+ decl %ecx
>> >+#define PUT(x) movnti %eax,x*8(%edi) ; movnti %eax,x*8+4(%edi)
>>
>> Is doing twice as much unrolling as on 64-bit really worth it?
>
> Moving 64 bytes per cycle is faster on Sandy Bridge, but slower on
> Westmere. Any preference? ;)
If it's not a clear win, I'd favor the 8-stores-per-cycle variant,
matching x86-64.
Jan
