[PATCH] arch64: optimize __memcpy_fromio, __memcpy_toio and __memset_io
From: Mark Salyzyn
Date: Fri Oct 20 2017 - 16:24:05 EST
__memcpy_fromio and __memcpy_toio functions do not deal well with
harmonically unaligned addresses unless they can ultimately be
copied as quads (u64) to and from the destination. Without a
harmonically aligned relationship, they perform byte operations
over the entire buffer.
Added optional paths that perform reads and writes at the best
alignment possible with source and destination, placing a priority
on using quads (8 byte transfers) on the io-side.
Removed the volatile on the source for __memcpy_toio as it is
unnecessary.
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 worst case 15ms, an improvement in boot time.
Adjusted __memset_io to use the same pattern of access, although it
does not have a harmonic relationship between two pointers to worry
about, and thus the benefit is balance and not nearly as dramatic.
Signed-off-by: Mark Salyzyn <salyzyn@xxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Anton Vorontsov <anton@xxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Anton Vorontsov <anton@xxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
arch/arm64/kernel/io.c | 199 ++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 156 insertions(+), 43 deletions(-)
diff --git a/arch/arm64/kernel/io.c b/arch/arm64/kernel/io.c
index 354be2a872ae..14ef7c8f20ea 100644
--- a/arch/arm64/kernel/io.c
+++ b/arch/arm64/kernel/io.c
@@ -20,61 +20,147 @@
#include <linux/types.h>
#include <linux/io.h>
+/* if/while helpers assume from, to and count vars accessible in caller */
+
+/* arguments to helpers to ensure proper combinations */
+#define byte b, u8
+#define word w, u16
+#define longword l, u32
+#define quad q, u64
+
+/* read helper for unaligned transfers needing intermediate hold and memcpy */
+#define _do_unaligned_read(op, align_type, width, type) do { \
+ op(count >= sizeof(type)) { \
+ type hold = __raw_read##width##(from); \
+ \
+ memcpy((align_type *)to, &hold, sizeof(type)); \
+ to += sizeof(type); \
+ from += sizeof(type); \
+ count -= sizeof(type); \
+ } \
+} while (0)
+#define if_unaligned_read(type, x) _do_unaligned_read(if, type, x)
+#define while_unaligned_read(type, x) _do_unaligned_read(while, type, x)
+
+/* read helper for aligned transfers */
+#define _do_aligned_read(op, width, type) \
+ _do_unaligned_read(op, type, width, type)
+#define if_aligned_read(x) _do_aligned_read(if, x)
+#define while_aligned_read(x) _do_aligned_read(while, x)
+
/*
* Copy data from IO memory space to "real" memory space.
*/
+
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))) {
- *(u8 *)to = __raw_readb(from);
- from++;
- to++;
- count--;
- }
+ if (!IS_ALIGNED((unsigned long)from, sizeof(u16)))
+ if_aligned_read(byte);
- while (count >= 8) {
- *(u64 *)to = __raw_readq(from);
- from += 8;
- to += 8;
- count -= 8;
+ if (!IS_ALIGNED((unsigned long)to, sizeof(u16))) {
+ if (!IS_ALIGNED((unsigned long)from, sizeof(u32)))
+ if_unaligned_read(u8, word);
+ if (!IS_ALIGNED((unsigned long)from, sizeof(u64)))
+ if_unaligned_read(u8, longword);
+ while_unaligned_read(u8, quad);
+ if_unaligned_read(u8, longword);
+ if_unaligned_read(u8, word);
+ if_aligned_read(byte);
+ return;
}
- while (count) {
- *(u8 *)to = __raw_readb(from);
- from++;
- to++;
- count--;
+ if (!IS_ALIGNED((unsigned long)from, sizeof(u32)))
+ if_aligned_read(word);
+
+ if (!IS_ALIGNED((unsigned long)to, sizeof(u32))) {
+ if (!IS_ALIGNED((unsigned long)from, sizeof(u64)))
+ if_unaligned_read(u16, longword);
+ while_unaligned_read(u16, quad);
+ if_unaligned_read(u16, longword);
+ if_aligned_read(word);
+ if_aligned_read(byte);
+ return;
}
+
+ if (!IS_ALIGNED((unsigned long)from, sizeof(u64)))
+ if_aligned_read(longword);
+
+ if (!IS_ALIGNED((unsigned long)to, sizeof(u64)))
+ while_unaligned_read(u32, quad);
+ else
+ while_aligned_read(quad);
+
+ if_aligned_read(longword);
+ if_aligned_read(word);
+ if_aligned_read(byte);
}
EXPORT_SYMBOL(__memcpy_fromio);
+/* write helper for unaligned transfers needing intermediate hold and memcpy */
+#define _do_unaligned_write(op, align_type, width, type) do { \
+ op(count >= sizeof(type)) { \
+ type hold; \
+ \
+ memcpy(&hold, (align_type *)from, sizeof(type));\
+ __raw_write##width##(hold, to); \
+ to += sizeof(type); \
+ from += sizeof(type); \
+ count -= sizeof(type); \
+ } \
+} while (0)
+#define if_unaligned_write(type, x) _do_unaligned_write(if, type, x)
+#define while_unaligned_write(type, x) _do_unaligned_write(while, type, x)
+
+/* write helper for aligned transfers */
+#define _do_aligned_write(op, width, type) \
+ _do_unaligned_write(op, type, width, type)
+#define if_aligned_write(x) _do_aligned_write(if, x)
+#define while_aligned_write(x) _do_aligned_write(while, x)
+
/*
* Copy data from "real" memory space to IO memory space.
*/
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);
- from++;
- to++;
- count--;
- }
+ if (!IS_ALIGNED((unsigned long)to, sizeof(u16)))
+ if_aligned_write(byte);
- while (count >= 8) {
- __raw_writeq(*(volatile u64 *)from, to);
- from += 8;
- to += 8;
- count -= 8;
+ if (!IS_ALIGNED((unsigned long)from, sizeof(u16))) {
+ if (!IS_ALIGNED((unsigned long)to, sizeof(u32)))
+ if_unaligned_write(u8, word);
+ if (!IS_ALIGNED((unsigned long)to, sizeof(u64)))
+ if_unaligned_write(u8, longword);
+ while_unaligned_write(u8, quad);
+ if_unaligned_write(u8, longword);
+ if_unaligned_write(u8, word);
+ if_aligned_write(byte);
+ return;
}
- while (count) {
- __raw_writeb(*(volatile u8 *)from, to);
- from++;
- to++;
- count--;
+ if (!IS_ALIGNED((unsigned long)to, sizeof(u32)))
+ if_aligned_write(word);
+
+ if (!IS_ALIGNED((unsigned long)from, sizeof(u32))) {
+ if (!IS_ALIGNED((unsigned long)to, sizeof(u64)))
+ if_unaligned_write(u16, longword);
+ while_unaligned_write(u16, quad);
+ if_unaligned_write(u16, longword);
+ if_aligned_write(word);
+ if_aligned_write(byte);
+ return;
}
+
+ if (!IS_ALIGNED((unsigned long)to, sizeof(u64)))
+ if_aligned_write(longword);
+
+ if (!IS_ALIGNED((unsigned long)from, sizeof(u64)))
+ while_unaligned_write(u32, quad);
+ else
+ while_aligned_write(quad);
+
+ if_aligned_write(longword);
+ if_aligned_write(word);
+ if_aligned_write(byte);
}
EXPORT_SYMBOL(__memcpy_toio);
@@ -89,22 +175,49 @@ void __memset_io(volatile void __iomem *dst, int c, size_t count)
qc |= qc << 16;
qc |= qc << 32;
- while (count && !IS_ALIGNED((unsigned long)dst, 8)) {
+ if ((count >= sizeof(u8)) &&
+ !IS_ALIGNED((unsigned long)dst, sizeof(u16))) {
__raw_writeb(c, dst);
- dst++;
- count--;
+ dst += sizeof(u8);
+ count -= sizeof(u8);
+ }
+
+ if ((count >= sizeof(u16)) &&
+ !IS_ALIGNED((unsigned long)dst, sizeof(u32))) {
+ __raw_writew((u16)qc, dst);
+ dst += sizeof(u16);
+ count -= sizeof(u16);
}
- while (count >= 8) {
+ if ((count >= sizeof(u32)) &&
+ !IS_ALIGNED((unsigned long)dst, sizeof(u64))) {
+ __raw_writel((u32)qc, dst);
+ dst += sizeof(u32);
+ count -= sizeof(u32);
+ }
+
+ while (count >= sizeof(u64)) {
__raw_writeq(qc, dst);
- dst += 8;
- count -= 8;
+ dst += sizeof(u64);
+ count -= sizeof(u64);
+ }
+
+ if (count >= sizeof(u32)) {
+ __raw_writel((u32)qc, dst);
+ dst += sizeof(u32);
+ count -= sizeof(u32);
+ }
+
+ if (count >= sizeof(u16)) {
+ __raw_writew((u16)qc, dst);
+ dst += sizeof(u16);
+ count -= sizeof(u16);
}
- while (count) {
+ if (count) {
__raw_writeb(c, dst);
- dst++;
- count--;
+ dst += sizeof(u8);
+ count -= sizeof(u8);
}
}
EXPORT_SYMBOL(__memset_io);
--
2.15.0.rc0.271.g36b669edcc-goog