diff options
| author | Anton Blanchard <anton@samba.org> | 2012-05-27 23:54:03 +0400 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2012-07-03 08:14:41 +0400 |
| commit | 17968fbbd19f1bb281ee4eb2548764ac5664c4ec (patch) | |
| tree | c6b7a68ea7897e6bf213bffa4795fe209609cba9 /arch/powerpc/lib/Makefile | |
| parent | d136e27326a3bd50d7929a43c018abf13e426b7e (diff) | |
| download | linux-17968fbbd19f1bb281ee4eb2548764ac5664c4ec.tar.xz | |
powerpc: 64bit optimised __clear_user
I noticed __clear_user high up in a profile of one of my RAID stress
tests. The testcase was doing a dd from /dev/zero which ends up
calling __clear_user.
__clear_user is basically a loop with a single 4 byte store which
is horribly slow. We can do much better by aligning the desination
and doing 32 bytes of 8 byte stores in a loop.
The following testcase was used to verify the patch:
http://ozlabs.org/~anton/junkcode/stress_clear_user.c
To show the improvement in performance I ran a dd from /dev/zero
to /dev/null on a POWER7 box:
Before:
# dd if=/dev/zero of=/dev/null bs=1M count=10000
10485760000 bytes (10 GB) copied, 3.72379 s, 2.8 GB/s
After:
# time dd if=/dev/zero of=/dev/null bs=1M count=10000
10485760000 bytes (10 GB) copied, 0.728318 s, 14.4 GB/s
Over 5x faster.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/lib/Makefile')
| -rw-r--r-- | arch/powerpc/lib/Makefile | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile index 7735a2c2e6d9..f049e339e456 100644 --- a/arch/powerpc/lib/Makefile +++ b/arch/powerpc/lib/Makefile @@ -17,7 +17,7 @@ obj-$(CONFIG_HAS_IOMEM) += devres.o obj-$(CONFIG_PPC64) += copypage_64.o copyuser_64.o \ memcpy_64.o usercopy_64.o mem_64.o string.o \ checksum_wrappers_64.o hweight_64.o \ - copyuser_power7.o + copyuser_power7.o string_64.o obj-$(CONFIG_XMON) += sstep.o ldstfp.o obj-$(CONFIG_KPROBES) += sstep.o ldstfp.o obj-$(CONFIG_HAVE_HW_BREAKPOINT) += sstep.o ldstfp.o |