Hi Michael,
Le 22/11/2019 à 07:38, Michael Ellerman a écrit :
Michael Ellerman <m...@ellerman.id.au> writes:
Christophe Leroy <christophe.le...@c-s.fr> writes:
__get_datapage() is only a few instructions to retrieve the
address of the page where the kernel stores data to the VDSO.
By inlining this function into its users, a bl/blr pair and
a mflr/mtlr pair is avoided, plus a few reg moves.
The improvement is noticeable (about 55 nsec/call on an 8xx)
vdsotest before the patch:
gettimeofday: vdso: 731 nsec/call
clock-gettime-realtime-coarse: vdso: 668 nsec/call
clock-gettime-monotonic-coarse: vdso: 745 nsec/call
vdsotest after the patch:
gettimeofday: vdso: 677 nsec/call
clock-gettime-realtime-coarse: vdso: 613 nsec/call
clock-gettime-monotonic-coarse: vdso: 690 nsec/call
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
This doesn't build with gcc 4.6.3:
/linux/arch/powerpc/kernel/vdso32/gettimeofday.S: Assembler messages:
/linux/arch/powerpc/kernel/vdso32/gettimeofday.S:41: Error: unsupported
relocation against __kernel_datapage_offset
/linux/arch/powerpc/kernel/vdso32/gettimeofday.S:86: Error: unsupported
relocation against __kernel_datapage_offset
/linux/arch/powerpc/kernel/vdso32/gettimeofday.S:213: Error: unsupported
relocation against __kernel_datapage_offset
/linux/arch/powerpc/kernel/vdso32/gettimeofday.S:247: Error: unsupported
relocation against __kernel_datapage_offset
make[4]: *** [arch/powerpc/kernel/vdso32/gettimeofday.o] Error 1
Actually I guess it's binutils, which is v2.22 in this case.
Needed this:
diff --git a/arch/powerpc/include/asm/vdso_datapage.h
b/arch/powerpc/include/asm/vdso_datapage.h
index 12785f72f17d..0048db347ddf 100644
--- a/arch/powerpc/include/asm/vdso_datapage.h
+++ b/arch/powerpc/include/asm/vdso_datapage.h
@@ -117,7 +117,7 @@ extern struct vdso_data *vdso_data;
.macro get_datapage ptr, tmp
bcl 20, 31, .+4
mflr \ptr
- addi \ptr, \ptr, __kernel_datapage_offset - (.-4)
+ addi \ptr, \ptr, (__kernel_datapage_offset - (.-4))@l
lwz \tmp, 0(\ptr)
add \ptr, \tmp, \ptr
.endm
Are you still planning to getting this series merged ? Do you need any
help / rebase / re-spin ?
Christophe
