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cb9dc92c0a
linux/arch/arm/lib
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Nicolas Pitre cb9dc92c0a [ARM] lower overhead with alternative copy_to_user for small copies 
Because the alternate copy_to_user implementation has a higher setup cost
than the standard implementation, the size of the memory area to copy
is tested and the standard implementation invoked instead when that size
is too small.  Still, that test is made after the processor has preserved
a bunch of registers on the stack which have to be reloaded right away
needlessly in that case, causing a measurable performance regression
compared to plain usage of the standard implementation only.

To make the size test overhead negligible, let's factorize it out of
the alternate copy_to_user function where it is clear to the compiler
that no stack frame is needed.  Thanks to CONFIG_ARM_UNWIND allowing
for frame pointers to be disabled and tail call optimization to kick in,
the overhead in the small copy case becomes only 3 assembly instructions.

A similar trick is applied to clear_user as well.

Signed-off-by: Nicolas Pitre <nico@marvell.com>
2009-05-29 22:38:33 -04:00
..
ashldi3.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
ashrdi3.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
backtrace.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
bitops.h [ARM] spelling fixes 2007-05-20 20:10:32 +01:00
changebit.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
clear_user.S [ARM] allow for alternative __copy_to_user/__clear_user implementations 2009-05-29 22:34:45 -04:00
clearbit.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
copy_from_user.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
copy_page.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
copy_template.S [ARM] cache align destination pointer when copying memory for some processors 2008-06-22 22:44:38 +02:00
copy_to_user.S [ARM] allow for alternative __copy_to_user/__clear_user implementations 2009-05-29 22:34:45 -04:00
csumipv6.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
csumpartial.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
csumpartialcopy.S [ARM] 5231/1: Do not save the frame pointer in the csum_partial_copy_* functions 2008-09-01 12:06:35 +01:00
csumpartialcopygeneric.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
csumpartialcopyuser.S [ARM] 5231/1: Do not save the frame pointer in the csum_partial_copy_* functions 2008-09-01 12:06:35 +01:00
delay.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
div64.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
ecard.S [ARM] Move include/asm-arm/arch-* to arch/arm/*/include/mach 2008-08-07 09:55:48 +01:00
findbit.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
floppydma.S Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
getuser.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
io-acorn.S [ARM] Remove unnecessary asm/hardware.h includes 2006-03-21 22:05:50 +00:00
io-readsb.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
io-readsl.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
io-readsw-armv3.S [ARM] Move include/asm-arm/arch-* to arch/arm/*/include/mach 2008-08-07 09:55:48 +01:00
io-readsw-armv4.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
io-shark.c [PATCH] ARM: 2815/1: Shark: new defconfig, fixes with __io and serial ports 2005-07-16 17:17:18 +01:00
io-writesb.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
io-writesl.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
io-writesw-armv3.S [ARM] Move include/asm-arm/arch-* to arch/arm/*/include/mach 2008-08-07 09:55:48 +01:00
io-writesw-armv4.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
lib1funcs.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
lshrdi3.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
Makefile [ARM] alternative copy_to_user/clear_user implementation 2009-05-29 22:36:45 -04:00
memchr.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
memcpy.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
memmove.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
memset.S [ARM] remove memzero() 2008-11-27 12:37:59 +00:00
memzero.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
muldi3.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
putuser.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
setbit.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
sha1.S Merge branch 'ptebits' into devel 2008-10-09 21:31:56 +01:00
strchr.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
strncpy_from_user.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
strnlen_user.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
strrchr.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
testchangebit.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
testclearbit.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
testsetbit.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
uaccess_with_memcpy.c [ARM] lower overhead with alternative copy_to_user for small copies 2009-05-29 22:38:33 -04:00
uaccess.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00
ucmpdi2.S [ARM] 5227/1: Add the ENDPROC declarations to the .S files 2008-09-01 12:06:34 +01:00