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authorMark Salyzyn <salyzyn@android.com>2017-10-24 07:47:14 -0700
committerWill Deacon <will.deacon@arm.com>2017-10-24 16:23:07 +0100
commit9ca255bf041ddc7698b6906dbd846c0ba64b1fe1 (patch)
tree868d2b06309b5441a2174dc5e124f75c63cda3a1 /arch/arm64/kernel/io.c
parent1e0c661f05ba0a3db52ed9debbe2b2e1d74aa0a4 (diff)
downloadlinux-9ca255bf041ddc7698b6906dbd846c0ba64b1fe1.tar.bz2
arm64: Avoid aligning normal memory pointers in __memcpy_{to,from}io
__memcpy_{to,from}io fall back to byte-at-a-time copying if both the source and destination pointers are not 8-byte aligned. Since one of the pointers always points at normal memory, this is unnecessary and detrimental to performance, so only do byte copying until we hit an 8-byte boundary for the device pointer. This change was motivated by performance issues in the pstore driver. On a test platform, measuring probe time for pstore, console buffer size of 1/4MB and pmsg of 1/2MB, was in the 90-107ms region. Change managed to reduce it to 10-25ms, an improvement in boot time. Cc: Kees Cook <keescook@chromium.org> Cc: Anton Vorontsov <anton@enomsg.org> Cc: Tony Luck <tony.luck@intel.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Anton Vorontsov <anton@enomsg.org> Cc: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Mark Salyzyn <salyzyn@android.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/io.c')
-rw-r--r--arch/arm64/kernel/io.c12
1 files changed, 5 insertions, 7 deletions
diff --git a/arch/arm64/kernel/io.c b/arch/arm64/kernel/io.c
index 354be2a872ae..79b17384effa 100644
--- a/arch/arm64/kernel/io.c
+++ b/arch/arm64/kernel/io.c
@@ -25,8 +25,7 @@
*/
void __memcpy_fromio(void *to, const volatile void __iomem *from, size_t count)
{
- while (count && (!IS_ALIGNED((unsigned long)from, 8) ||
- !IS_ALIGNED((unsigned long)to, 8))) {
+ while (count && !IS_ALIGNED((unsigned long)from, 8)) {
*(u8 *)to = __raw_readb(from);
from++;
to++;
@@ -54,23 +53,22 @@ EXPORT_SYMBOL(__memcpy_fromio);
*/
void __memcpy_toio(volatile void __iomem *to, const void *from, size_t count)
{
- while (count && (!IS_ALIGNED((unsigned long)to, 8) ||
- !IS_ALIGNED((unsigned long)from, 8))) {
- __raw_writeb(*(volatile u8 *)from, to);
+ while (count && !IS_ALIGNED((unsigned long)to, 8)) {
+ __raw_writeb(*(u8 *)from, to);
from++;
to++;
count--;
}
while (count >= 8) {
- __raw_writeq(*(volatile u64 *)from, to);
+ __raw_writeq(*(u64 *)from, to);
from += 8;
to += 8;
count -= 8;
}
while (count) {
- __raw_writeb(*(volatile u8 *)from, to);
+ __raw_writeb(*(u8 *)from, to);
from++;
to++;
count--;