The patch titled
iommu: inline iommu_num_pages
has been added to the -mm tree. Its filename is
iommu-inline-iommu_num_pages.patch
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------------------------------------------------------
Subject: iommu: inline iommu_num_pages
From: Anton Blanchard <anton@xxxxxxxxx>
A profile of a network benchmark showed iommu_num_pages rather high up:
0.52% iommu_num_pages
Looking at the profile, an integer divide is taking almost all of the time:
%
: c000000000376ea4 <.iommu_num_pages>:
1.93 : c000000000376ea4: fb e1 ff f8 std r31,-8(r1)
0.00 : c000000000376ea8: f8 21 ff c1 stdu r1,-64(r1)
0.00 : c000000000376eac: 7c 3f 0b 78 mr r31,r1
3.86 : c000000000376eb0: 38 84 ff ff addi r4,r4,-1
0.00 : c000000000376eb4: 38 05 ff ff addi r0,r5,-1
0.00 : c000000000376eb8: 7c 84 2a 14 add r4,r4,r5
46.95 : c000000000376ebc: 7c 00 18 38 and r0,r0,r3
45.66 : c000000000376ec0: 7c 84 02 14 add r4,r4,r0
0.00 : c000000000376ec4: 7c 64 2b 92 divdu r3,r4,r5
0.00 : c000000000376ec8: 38 3f 00 40 addi r1,r31,64
0.00 : c000000000376ecc: eb e1 ff f8 ld r31,-8(r1)
1.61 : c000000000376ed0: 4e 80 00 20 blr
Since every caller of iommu_num_pages passes in a constant power of two
we can inline this such that the divide is replaced by a shift. The
entire function is only a few instructions once optimised, so it is
a good candidate for inlining overall.
Signed-off-by: Anton Blanchard <anton@xxxxxxxxx>
Cc: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/iommu-helper.h | 12 ++++++++++--
lib/iommu-helper.c | 9 ---------
2 files changed, 10 insertions(+), 11 deletions(-)
diff -puN include/linux/iommu-helper.h~iommu-inline-iommu_num_pages include/linux/iommu-helper.h
--- a/include/linux/iommu-helper.h~iommu-inline-iommu_num_pages
+++ a/include/linux/iommu-helper.h
@@ -1,6 +1,8 @@
#ifndef _LINUX_IOMMU_HELPER_H
#define _LINUX_IOMMU_HELPER_H
+#include <linux/kernel.h>
+
static inline unsigned long iommu_device_max_index(unsigned long size,
unsigned long offset,
u64 dma_mask)
@@ -20,7 +22,13 @@ extern unsigned long iommu_area_alloc(un
unsigned long boundary_size,
unsigned long align_mask);
-extern unsigned long iommu_num_pages(unsigned long addr, unsigned long len,
- unsigned long io_page_size);
+static inline unsigned long iommu_num_pages(unsigned long addr,
+ unsigned long len,
+ unsigned long io_page_size)
+{
+ unsigned long size = (addr & (io_page_size - 1)) + len;
+
+ return DIV_ROUND_UP(size, io_page_size);
+}
#endif
diff -puN lib/iommu-helper.c~iommu-inline-iommu_num_pages lib/iommu-helper.c
--- a/lib/iommu-helper.c~iommu-inline-iommu_num_pages
+++ a/lib/iommu-helper.c
@@ -38,12 +38,3 @@ again:
return -1;
}
EXPORT_SYMBOL(iommu_area_alloc);
-
-unsigned long iommu_num_pages(unsigned long addr, unsigned long len,
- unsigned long io_page_size)
-{
- unsigned long size = (addr & (io_page_size - 1)) + len;
-
- return DIV_ROUND_UP(size, io_page_size);
-}
-EXPORT_SYMBOL(iommu_num_pages);
_
Patches currently in -mm which might be from anton@xxxxxxxxx are
linux-next.patch
iommu-inline-iommu_num_pages.patch
panic-keep-blinking-in-spite-of-long-spin-timer-mode.patch
lib-bugc-make-warn-implementation-match-the-kernel-panicc-one.patch
lib-bugc-make-warn-implementation-match-the-kernel-panicc-one-checkpatch-fixes.patch
add-oops-end-marker-to-lib-bugc-warn-implementation.patch
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