From 3f33a7c8ceeefd769a68bbcc2ed3e4ce74ddaef8 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@users.noreply.github.com>
Date: Mon, 4 Jun 2018 09:32:32 +0200
Subject: consensus/ethash: reduce keccak hash allocations (#16857)
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Use Read instead of Sum to avoid internal allocations and
copying the state.
name old time/op new time/op delta
CacheGeneration-8 764ms ± 1% 579ms ± 1% -24.22% (p=0.000 n=20+17)
SmallDatasetGeneration-8 75.2ms ±12% 60.6ms ±10% -19.37% (p=0.000 n=20+20)
HashimotoLight-8 1.58ms ±11% 1.55ms ± 8% ~ (p=0.322 n=20+19)
HashimotoFullSmall-8 4.90µs ± 1% 4.88µs ± 1% -0.31% (p=0.013 n=19+18)
---
consensus/ethash/algorithm.go | 23 +++++++++++++++++------
1 file changed, 17 insertions(+), 6 deletions(-)
(limited to 'consensus')
diff --git a/consensus/ethash/algorithm.go b/consensus/ethash/algorithm.go
index 905a7b1ea..fa1c2c824 100644
--- a/consensus/ethash/algorithm.go
+++ b/consensus/ethash/algorithm.go
@@ -94,14 +94,25 @@ func calcDatasetSize(epoch int) uint64 {
// reused between hash runs instead of requiring new ones to be created.
type hasher func(dest []byte, data []byte)
-// makeHasher creates a repetitive hasher, allowing the same hash data structures
-// to be reused between hash runs instead of requiring new ones to be created.
-// The returned function is not thread safe!
+// makeHasher creates a repetitive hasher, allowing the same hash data structures to
+// be reused between hash runs instead of requiring new ones to be created. The returned
+// function is not thread safe!
func makeHasher(h hash.Hash) hasher {
+ // sha3.state supports Read to get the sum, use it to avoid the overhead of Sum.
+ // Read alters the state but we reset the hash before every operation.
+ type readerHash interface {
+ hash.Hash
+ Read([]byte) (int, error)
+ }
+ rh, ok := h.(readerHash)
+ if !ok {
+ panic("can't find Read method on hash")
+ }
+ outputLen := rh.Size()
return func(dest []byte, data []byte) {
- h.Write(data)
- h.Sum(dest[:0])
- h.Reset()
+ rh.Reset()
+ rh.Write(data)
+ rh.Read(dest[:outputLen])
}
}
--
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