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arm64: Avoid aligning normal memory pointers in __memcpy_{to,from}io

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__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>
This commit is contained in:
Mark Salyzyn 2017-10-24 07:47:14 -07:00 committed by Will Deacon
parent 1e0c661f05
commit 9ca255bf04
1 changed files with 5 additions and 7 deletions
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12
arch/arm64/kernel/io.c
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@ -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--;