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SubjectRe: [SUGGESTION]: drop virtual merge accounting in I/O requests
On Mon, 14 Jul 2008, David Miller wrote:

> From: Mikulas Patocka <mpatocka@redhat.com>
> Date: Mon, 14 Jul 2008 19:16:17 -0400 (EDT)
>
> > So the question is: to reduce number of requests by 12% on an outdated
> > SCSI card, it is sensible to maintain complicated merge accounting logic
> > in the core block layer? To me, it doesn't seem sensible.
>
> Rip out the code if you like, then. I really don't have time to
> work on this myself. So if you do, by all means do whatever
> you think is appropriate.

So add signed-off line and forward it to Linus.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
---
include/asm-sparc64/io.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
Index: linux-2.6.26-fast/include/asm-sparc64/io.h
===================================================================
--- linux-2.6.26-fast.orig/include/asm-sparc64/io.h 2008-07-15 23:29:39.000000000 +0200
+++ linux-2.6.26-fast/include/asm-sparc64/io.h 2008-07-15 23:33:41.000000000 +0200
@@ -16,7 +16,10 @@
/* BIO layer definitions. */
extern unsigned long kern_base, kern_size;
#define page_to_phys(page) (page_to_pfn(page) << PAGE_SHIFT)
-#define BIO_VMERGE_BOUNDARY 8192
+
+/* Don't declare that we are virtual-merge capable because Sparc64 IOMMU code
+ doesn't guarantee that the merge is always possible */
+#define BIO_VMERGE_BOUNDARY 0

static inline u8 _inb(unsigned long addr)
{

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