80516ed335
On my machine, reading 512-byte blocks from /dev/urandom
(same via getentropy syscall) is a lot faster in terms of
throughput:
Blocksize Throughput
16 28.18 MB/s
512 83.75 MB/s
For a single-threaded streaming write, this drops the CPU usage of
nonceGenerator.Get to almost 1/3:
flat flat% sum% cum cum%
Before 0 0% 95.08% 0.35s 2.92% github.com/rfjakob/gocryptfs/internal/cryptocore.(*nonceGenerator).Get
After 0.01s 0.092% 92.34% 0.13s 1.20% github.com/rfjakob/gocryptfs/internal/cryptocore.(*nonceGenerator).Get
This change makes the nonce reading single-threaded, which may
hurt massively-parallel writes.
41 lines
793 B
Go
41 lines
793 B
Go
package cryptocore
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import (
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"bytes"
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"compress/flate"
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"runtime"
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"sync"
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"testing"
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)
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// TestRandPrefetch hammers the randPrefetcher with 100 goroutines and verifies
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// that the result is incompressible
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func TestRandPrefetch(t *testing.T) {
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runtime.GOMAXPROCS(10)
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p := 100
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l := 200
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vec := make([][]byte, p)
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var wg sync.WaitGroup
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for i := 0; i < p; i++ {
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wg.Add(1)
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go func(i int) {
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var tmp []byte
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for x := 0; x < l; x++ {
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tmp = append(tmp, randPrefetcher.read(l)...)
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}
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vec[i] = tmp
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wg.Done()
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}(i)
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}
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wg.Wait()
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var b bytes.Buffer
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fw, _ := flate.NewWriter(&b, flate.BestCompression)
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for _, v := range vec {
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fw.Write(v)
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}
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fw.Close()
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if b.Len() < p*l*l {
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t.Errorf("random data should be incompressible, but: in=%d compressed=%d\n", p*l*l, b.Len())
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}
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}
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