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engine: page defragmentation #202

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engine: page defragmentation #202

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aa188d7
bench: page defragment
ayzu Jul 12, 2020
6d17cb2
fix a typo
ayzu Jul 12, 2020
15ee4ec
ref: use b.Fatal()
ayzu Jul 12, 2020
2b1e267
a typo
ayzu Jul 12, 2020
1598dd1
Merge branch 'master' into bench-defragment
tsatke Jul 19, 2020
0d50af1
Merge branch 'master' into bench-defragment
tsatke Jul 20, 2020
da03cc3
Merge branch 'master' into bench-defragment
tsatke Jul 27, 2020
edd5399
Merge branch 'master' into bench-defragment
tsatke Jul 31, 2020
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2 changes: 1 addition & 1 deletion internal/engine/storage/page/page.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ import (
const (
// Size is the fix size of a page, which is 16KB or 16384 bytes.
Size = 1 << 14
// HeaderSize is the fix size of a page header, which is 10 bytes.
// HeaderSize is the fix size of a page header, which is 6 bytes.
HeaderSize = 6
)

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63 changes: 63 additions & 0 deletions internal/engine/storage/page/page_bench_test.go
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@@ -0,0 +1,63 @@
package page
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Please read the contribution and coding guidelines.


import (
"math"
"math/rand"
"testing"
)

const (
maxKeySize = 100
maxRecordSize = 1_000
)

var (
pageSize = int(math.Round(2 * float64(Size) / 3)) // two-thirds of the max size
)

func generateRecordCell(b *testing.B) RecordCell {
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Ordering: exported before unexported

keySize := 1 + rand.Intn(maxKeySize-1)
recordSize := 1 + rand.Intn(maxRecordSize-1)
Comment on lines +19 to +20
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Please use an explicitely seeded random source, to be sure that the test is always reproducible, regardless of someone else seeding the whole rand package or not.

key, record := make([]byte, keySize), make([]byte, recordSize)
_, err := rand.Read(key)
if err != nil {
b.Fatal(err)
}
Comment on lines +23 to +25
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We tend to use stretchr/testify for tests.
You could easily rewrite this as

assert := assert.New(b)
...
_, err := rand.Read(key)
assert.NoError(err)
...

And you would get rid of a lot of err checks like this.

_, err = rand.Read(record)
if err != nil {
b.Fatal(err)
}

return RecordCell{
Key: key,
Record: record,
}
}

func generatePage(b *testing.B) *Page {
b.Helper()
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Why is this a helper, but generateCell isn't?

p, err := load(make([]byte, pageSize))
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Why only use a page with 2 thirds of the total size? Is that benchmark still representative if the page is smaller than 16K?

if err != nil {
b.Fatal(err)
}
record := generateRecordCell(b)
for err = p.StoreRecordCell(record); err != ErrPageFull; err = p.StoreRecordCell(record) {
record = generateRecordCell(b)
}
Comment on lines +43 to +46
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Suggested change
record := generateRecordCell(b)
for err = p.StoreRecordCell(record); err != ErrPageFull; err = p.StoreRecordCell(record) {
record = generateRecordCell(b)
}
for {
rec := generateRecordCell(b)
if err := p.StoreRecordCell(rec); err != nil {
assert.Equal(ErrPageFull, err)
break
}
}

return p
}

func BenchmarkPage_Defragment(b *testing.B) {
data := generatePage(b).data
bytes := make([]byte, len(data))
b.ResetTimer()
b.ReportAllocs()

for i := 0; i < b.N; i++ {
copy(bytes, data)
Comment on lines +51 to +57
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page.RawData() does exactly that, return a copy of the page data. That way, you don't need to access unexported fields.

page := &Page{ // have to recreate a page with initial data
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Use Load rather than this. This does work, however, if the page implementation changes, this probably doesn't work any more (e.g. adding locks or cell caches as maps etc)

data: bytes,
}
Comment on lines +57 to +60
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This should probably not be part of the benchmark, exclude it with b.StopTimer() and b.StartTimer() respectively

page.Defragment()
}
}