Hi all powerpc64 experts,
While looking at the usercopy efficiency for PPC32, I noticed something
which looks strange.
In asm/uaccess.h, raw_copy_from_user() and raw_copy_to_user() implements
a fast path using get_user() and put_user() for copies of constant size < 8.
But INLINE_COPY_FROM_USER and INLINE_COPY_TO_USER are only defined for
PPC32, so PPC64 will call __copy_tofrom_user() even for small constant
size copies. Is that wanted ?
Regards
Christophe
Le 30/05/2017 à 14:36, Christophe LEROY a écrit :
Hi all powerpc64 experts,
While looking at the usercopy efficiency for PPC32, I noticed something
which looks strange.
In asm/uaccess.h, raw_copy_from_user() and raw_copy_to_user() implements
a fast path using get_user() and put_user() for copies of constant size
< 8.
But INLINE_COPY_FROM_USER and INLINE_COPY_TO_USER are only defined for
PPC32, so PPC64 will call __copy_tofrom_user() even for small constant
size copies. Is that wanted ?
I tried and built ppc64_defconfig with and without INLINE_COPY_xxx_USER,
I got the following result:
Without INLINE_COPY_xxx_USER:
System.map:c0000000009b2000 A _etext
With INLINE_COPY_xxx_USER:
System.map:c0000000009c1000 A _etext
So the size increase with inlining is only 0,6%
Wouldn't it be worth it ?
Christophe