components/golang/patches/0030-release-branch.go1.5-runtime-adjust-the-arm64-memmov.patch
From d3a413569bf5c01cf08a24bc6b13fd331081b842 Mon Sep 17 00:00:00 2001
From: Michael Hudson-Doyle <[email protected]>
Date: Tue, 22 Sep 2015 14:34:39 +1200
Subject: [PATCH 30/63] [release-branch.go1.5] runtime: adjust the arm64
memmove and memclr to operate by word as much as they can
Not only is this an obvious optimization:
benchmark old MB/s new MB/s speedup
BenchmarkMemmove1-4 35.35 29.65 0.84x
BenchmarkMemmove2-4 63.78 52.53 0.82x
BenchmarkMemmove3-4 89.72 73.96 0.82x
BenchmarkMemmove4-4 109.94 95.73 0.87x
BenchmarkMemmove5-4 127.60 112.80 0.88x
BenchmarkMemmove6-4 143.59 126.67 0.88x
BenchmarkMemmove7-4 157.90 138.92 0.88x
BenchmarkMemmove8-4 167.18 231.81 1.39x
BenchmarkMemmove9-4 175.23 252.07 1.44x
BenchmarkMemmove10-4 165.68 261.10 1.58x
BenchmarkMemmove11-4 174.43 263.31 1.51x
BenchmarkMemmove12-4 180.76 267.56 1.48x
BenchmarkMemmove13-4 189.06 284.93 1.51x
BenchmarkMemmove14-4 186.31 284.72 1.53x
BenchmarkMemmove15-4 195.75 281.62 1.44x
BenchmarkMemmove16-4 202.96 439.23 2.16x
BenchmarkMemmove32-4 264.77 775.77 2.93x
BenchmarkMemmove64-4 306.81 1209.64 3.94x
BenchmarkMemmove128-4 357.03 1515.41 4.24x
BenchmarkMemmove256-4 380.77 2066.01 5.43x
BenchmarkMemmove512-4 385.05 2556.45 6.64x
BenchmarkMemmove1024-4 381.23 2804.10 7.36x
BenchmarkMemmove2048-4 379.06 2814.83 7.43x
BenchmarkMemmove4096-4 387.43 3064.96 7.91x
BenchmarkMemmoveUnaligned1-4 28.91 25.40 0.88x
BenchmarkMemmoveUnaligned2-4 56.13 47.56 0.85x
BenchmarkMemmoveUnaligned3-4 74.32 69.31 0.93x
BenchmarkMemmoveUnaligned4-4 97.02 83.58 0.86x
BenchmarkMemmoveUnaligned5-4 110.17 103.62 0.94x
BenchmarkMemmoveUnaligned6-4 124.95 113.26 0.91x
BenchmarkMemmoveUnaligned7-4 142.37 130.82 0.92x
BenchmarkMemmoveUnaligned8-4 151.20 205.64 1.36x
BenchmarkMemmoveUnaligned9-4 166.97 215.42 1.29x
BenchmarkMemmoveUnaligned10-4 148.49 221.22 1.49x
BenchmarkMemmoveUnaligned11-4 159.47 239.57 1.50x
BenchmarkMemmoveUnaligned12-4 163.52 247.32 1.51x
BenchmarkMemmoveUnaligned13-4 167.55 256.54 1.53x
BenchmarkMemmoveUnaligned14-4 175.12 251.03 1.43x
BenchmarkMemmoveUnaligned15-4 192.10 267.13 1.39x
BenchmarkMemmoveUnaligned16-4 190.76 378.87 1.99x
BenchmarkMemmoveUnaligned32-4 259.02 562.98 2.17x
BenchmarkMemmoveUnaligned64-4 317.72 842.44 2.65x
BenchmarkMemmoveUnaligned128-4 355.43 1274.49 3.59x
BenchmarkMemmoveUnaligned256-4 378.17 1815.74 4.80x
BenchmarkMemmoveUnaligned512-4 362.15 2180.81 6.02x
BenchmarkMemmoveUnaligned1024-4 376.07 2453.58 6.52x
BenchmarkMemmoveUnaligned2048-4 381.66 2568.32 6.73x
BenchmarkMemmoveUnaligned4096-4 398.51 2669.36 6.70x
BenchmarkMemclr5-4 113.83 107.93 0.95x
BenchmarkMemclr16-4 223.84 389.63 1.74x
BenchmarkMemclr64-4 421.99 1209.58 2.87x
BenchmarkMemclr256-4 525.94 2411.58 4.59x
BenchmarkMemclr4096-4 581.66 4372.20 7.52x
BenchmarkMemclr65536-4 565.84 4747.48 8.39x
BenchmarkGoMemclr5-4 194.63 160.31 0.82x
BenchmarkGoMemclr16-4 295.30 630.07 2.13x
BenchmarkGoMemclr64-4 480.24 1884.03 3.92x
BenchmarkGoMemclr256-4 540.23 2926.49 5.42x
but it turns out that it's necessary to avoid the GC seeing partially written
pointers.
It's of course possible to be more sophisticated (using ldp/stp to move 16
bytes at a time in the core loop and unrolling the tail copying loops being
the obvious ideas) but I wanted something simple and (reasonably) obviously
correct.
Fixes #12552
Change-Id: Iaeaf8a812cd06f4747ba2f792de1ded738890735
Reviewed-on: https://go-review.googlesource.com/14813
Reviewed-by: Austin Clements <[email protected]>
Reviewed-on: https://go-review.googlesource.com/16909
Reviewed-by: Russ Cox <[email protected]>
---
src/runtime/memclr_arm64.s | 29 +++++++++++++---
src/runtime/memmove_arm64.s | 81 +++++++++++++++++++++++++++++++++++++--------
src/runtime/memmove_test.go | 35 ++++++++++++++++++++
3 files changed, 127 insertions(+), 18 deletions(-)
diff --git a/src/runtime/memclr_arm64.s b/src/runtime/memclr_arm64.s
index c44c123..47c6b73 100644
--- a/src/runtime/memclr_arm64.s
+++ b/src/runtime/memclr_arm64.s
@@ -8,11 +8,30 @@
TEXT runtime·memclr(SB),NOSPLIT,$0-16
MOVD ptr+0(FP), R3
MOVD n+8(FP), R4
- CMP $0, R4
- BEQ done
- ADD R3, R4, R4
+ // TODO(mwhudson): this is written this way to avoid tickling
+ // warnings from addpool when written as AND $7, R4, R6 (see
+ // https://golang.org/issue/12708)
+ AND $~7, R4, R5 // R5 is N&~7
+ SUB R5, R4, R6 // R6 is N&7
+
+ CMP $0, R5
+ BEQ nowords
+
+ ADD R3, R5, R5
+
+wordloop: // TODO: Optimize for unaligned ptr.
+ MOVD.P $0, 8(R3)
+ CMP R3, R5
+ BNE wordloop
+nowords:
+ CMP $0, R6
+ BEQ done
+
+ ADD R3, R6, R6
+
+byteloop:
MOVBU.P $0, 1(R3)
- CMP R3, R4
- BNE -2(PC)
+ CMP R3, R6
+ BNE byteloop
done:
RET
diff --git a/src/runtime/memmove_arm64.s b/src/runtime/memmove_arm64.s
index 66059a7..00813d4 100644
--- a/src/runtime/memmove_arm64.s
+++ b/src/runtime/memmove_arm64.s
@@ -14,23 +14,78 @@ TEXT runtime·memmove(SB), NOSPLIT, $-8-24
RET
check:
+ AND $~7, R5, R7 // R7 is N&~7
+ // TODO(mwhudson): this is written this way to avoid tickling
+ // warnings from addpool when written as AND $7, R5, R6 (see
+ // https://golang.org/issue/12708)
+ SUB R7, R5, R6 // R6 is N&7
+
CMP R3, R4
BLT backward
- ADD R3, R5
-loop:
- MOVBU.P 1(R4), R6
- MOVBU.P R6, 1(R3)
- CMP R3, R5
- BNE loop
+ // Copying forward proceeds by copying R7/8 words then copying R6 bytes.
+ // R3 and R4 are advanced as we copy.
+
+ // (There may be implementations of armv8 where copying by bytes until
+ // at least one of source or dest is word aligned is a worthwhile
+ // optimization, but the on the one tested so far (xgene) it did not
+ // make a significance difference.)
+
+ CMP $0, R7 // Do we need to do any word-by-word copying?
+ BEQ noforwardlarge
+
+ ADD R3, R7, R9 // R9 points just past where we copy by word
+
+forwardlargeloop:
+ MOVD.P 8(R4), R8 // R8 is just a scratch register
+ MOVD.P R8, 8(R3)
+ CMP R3, R9
+ BNE forwardlargeloop
+
+noforwardlarge:
+ CMP $0, R6 // Do we need to do any byte-by-byte copying?
+ BNE forwardtail
+ RET
+
+forwardtail:
+ ADD R3, R6, R9 // R9 points just past the destination memory
+
+forwardtailloop:
+ MOVBU.P 1(R4), R8
+ MOVBU.P R8, 1(R3)
+ CMP R3, R9
+ BNE forwardtailloop
RET
backward:
- ADD R5, R4
- ADD R3, R5
-loop1:
- MOVBU.W -1(R4), R6
- MOVBU.W R6, -1(R5)
- CMP R3, R5
- BNE loop1
+ // Copying backwards proceeds by copying R6 bytes then copying R7/8 words.
+ // R3 and R4 are advanced to the end of the destination/source buffers
+ // respectively and moved back as we copy.
+
+ ADD R4, R5, R4 // R4 points just past the last source byte
+ ADD R3, R5, R3 // R3 points just past the last destination byte
+
+ CMP $0, R6 // Do we need to do any byte-by-byte copying?
+ BEQ nobackwardtail
+
+ SUB R6, R3, R9 // R9 points at the lowest destination byte that should be copied by byte.
+backwardtailloop:
+ MOVBU.W -1(R4), R8
+ MOVBU.W R8, -1(R3)
+ CMP R9, R3
+ BNE backwardtailloop
+
+nobackwardtail:
+ CMP $0, R7 // Do we need to do any word-by-word copying?
+ BNE backwardlarge
+ RET
+
+backwardlarge:
+ SUB R7, R3, R9 // R9 points at the lowest destination byte
+
+backwardlargeloop:
+ MOVD.W -8(R4), R8
+ MOVD.W R8, -8(R3)
+ CMP R9, R3
+ BNE backwardlargeloop
RET
diff --git a/src/runtime/memmove_test.go b/src/runtime/memmove_test.go
index 857f99b..d5a2ad8 100644
--- a/src/runtime/memmove_test.go
+++ b/src/runtime/memmove_test.go
@@ -116,6 +116,41 @@ func BenchmarkMemmove1024(b *testing.B) { bmMemmove(b, 1024) }
func BenchmarkMemmove2048(b *testing.B) { bmMemmove(b, 2048) }
func BenchmarkMemmove4096(b *testing.B) { bmMemmove(b, 4096) }
+func bmMemmoveUnaligned(b *testing.B, n int) {
+ x := make([]byte, n+1)
+ y := make([]byte, n)
+ b.SetBytes(int64(n))
+ for i := 0; i < b.N; i++ {
+ copy(x[1:], y)
+ }
+}
+
+func BenchmarkMemmoveUnaligned0(b *testing.B) { bmMemmoveUnaligned(b, 0) }
+func BenchmarkMemmoveUnaligned1(b *testing.B) { bmMemmoveUnaligned(b, 1) }
+func BenchmarkMemmoveUnaligned2(b *testing.B) { bmMemmoveUnaligned(b, 2) }
+func BenchmarkMemmoveUnaligned3(b *testing.B) { bmMemmoveUnaligned(b, 3) }
+func BenchmarkMemmoveUnaligned4(b *testing.B) { bmMemmoveUnaligned(b, 4) }
+func BenchmarkMemmoveUnaligned5(b *testing.B) { bmMemmoveUnaligned(b, 5) }
+func BenchmarkMemmoveUnaligned6(b *testing.B) { bmMemmoveUnaligned(b, 6) }
+func BenchmarkMemmoveUnaligned7(b *testing.B) { bmMemmoveUnaligned(b, 7) }
+func BenchmarkMemmoveUnaligned8(b *testing.B) { bmMemmoveUnaligned(b, 8) }
+func BenchmarkMemmoveUnaligned9(b *testing.B) { bmMemmoveUnaligned(b, 9) }
+func BenchmarkMemmoveUnaligned10(b *testing.B) { bmMemmoveUnaligned(b, 10) }
+func BenchmarkMemmoveUnaligned11(b *testing.B) { bmMemmoveUnaligned(b, 11) }
+func BenchmarkMemmoveUnaligned12(b *testing.B) { bmMemmoveUnaligned(b, 12) }
+func BenchmarkMemmoveUnaligned13(b *testing.B) { bmMemmoveUnaligned(b, 13) }
+func BenchmarkMemmoveUnaligned14(b *testing.B) { bmMemmoveUnaligned(b, 14) }
+func BenchmarkMemmoveUnaligned15(b *testing.B) { bmMemmoveUnaligned(b, 15) }
+func BenchmarkMemmoveUnaligned16(b *testing.B) { bmMemmoveUnaligned(b, 16) }
+func BenchmarkMemmoveUnaligned32(b *testing.B) { bmMemmoveUnaligned(b, 32) }
+func BenchmarkMemmoveUnaligned64(b *testing.B) { bmMemmoveUnaligned(b, 64) }
+func BenchmarkMemmoveUnaligned128(b *testing.B) { bmMemmoveUnaligned(b, 128) }
+func BenchmarkMemmoveUnaligned256(b *testing.B) { bmMemmoveUnaligned(b, 256) }
+func BenchmarkMemmoveUnaligned512(b *testing.B) { bmMemmoveUnaligned(b, 512) }
+func BenchmarkMemmoveUnaligned1024(b *testing.B) { bmMemmoveUnaligned(b, 1024) }
+func BenchmarkMemmoveUnaligned2048(b *testing.B) { bmMemmoveUnaligned(b, 2048) }
+func BenchmarkMemmoveUnaligned4096(b *testing.B) { bmMemmoveUnaligned(b, 4096) }
+
func TestMemclr(t *testing.T) {
size := 512
if testing.Short() {
--
2.6.1