>>> On 09.08.12 at 17:03, "Kirill A. Shutemov"
>>> <kirill.shute...@linux.intel.com> wrote:
> From: Andi Kleen <a...@linux.intel.com>
>
> Add a cache avoiding version of clear_page. Straight forward integer variant
> of the existing 64bit clear_page, for both 32bit and 64bit.
While on 64-bit this is fine, I fail to see how you avoid using the
SSE2 instruction on non-SSE2 systems.
> Also add the necessary glue for highmem including a layer that non cache
> coherent architectures that use the virtual address for flushing can
> hook in. This is not needed on x86 of course.
>
> If an architecture wants to provide cache avoiding version of clear_page
> it should to define ARCH_HAS_USER_NOCACHE to 1 and implement
> clear_page_nocache() and clear_user_highpage_nocache().
>
> Signed-off-by: Andi Kleen <a...@linux.intel.com>
> Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
> ---
> 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?
> arch/x86/mm/fault.c | 7 +++++++
> 7 files changed, 79 insertions(+), 0 deletions(-)
> create mode 100644 arch/x86/lib/clear_page_nocache_32.S
> create mode 100644 arch/x86/lib/clear_page_nocache_64.S
>...
>--- /dev/null
>+++ b/arch/x86/lib/clear_page_nocache_32.S
>@@ -0,0 +1,30 @@
>+#include <linux/linkage.h>
>+#include <asm/dwarf2.h>
>+
>+/*
>+ * Zero a page avoiding the caches
>+ * rdi page
Wrong comment.
>+ */
>+ENTRY(clear_page_nocache)
>+ CFI_STARTPROC
>+ mov %eax,%edi
You need to pick a different register here (e.g. %edx), since
%edi has to be preserved by all functions called from C.
>+ 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?
Jan
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