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Optimize ListPostings Next() (#12906)
The Next() call of ListPostings() was updating two values, while we can
just update the position. This is up to 30% faster for high number of
Postings.
goos: linux
goarch: amd64
pkg: github.com/prometheus/prometheus/tsdb/index
cpu: 11th Gen Intel(R) Core(TM) i7-11700K @ 3.60GHz
│ old │ new │
│ sec/op │ sec/op vs base │
ListPostings/count=100-16 819.2n ± 0% 732.6n ± 0% -10.58% (p=0.000 n=20)
ListPostings/count=1000-16 2.685µ ± 1% 2.017µ ± 0% -24.88% (p=0.000 n=20)
ListPostings/count=10000-16 21.43µ ± 1% 14.81µ ± 0% -30.91% (p=0.000 n=20)
ListPostings/count=100000-16 209.4µ ± 1% 143.3µ ± 0% -31.55% (p=0.000 n=20)
ListPostings/count=1000000-16 2.086m ± 1% 1.436m ± 1% -31.18% (p=0.000 n=20)
geomean 29.02µ 21.41µ -26.22%
We're talking about microseconds here, but they just keep adding.
Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>
This commit is contained in:
Oleg Zaytsev
GitHub
parent
de7e057d3c
commit
1492031ef2
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@ -747,7 +747,7 @@ func (rp *removedPostings) Err() error {
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// ListPostings implements the Postings interface over a plain list.
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type ListPostings struct {
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list []storage.SeriesRef
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cur storage.SeriesRef
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pos int
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}
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func NewListPostings(list []storage.SeriesRef) Postings {
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@ -759,39 +759,34 @@ func newListPostings(list ...storage.SeriesRef) *ListPostings {
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}
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func (it *ListPostings) At() storage.SeriesRef {
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return it.cur
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return it.list[it.pos-1]
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}
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func (it *ListPostings) Next() bool {
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if len(it.list) > 0 {
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it.cur = it.list[0]
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it.list = it.list[1:]
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if it.pos < len(it.list) {
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it.pos++
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return true
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}
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it.cur = 0
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return false
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}
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func (it *ListPostings) Seek(x storage.SeriesRef) bool {
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// If the current value satisfies, then return.
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if it.cur >= x {
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return true
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if it.pos == 0 {
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it.pos++
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}
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if len(it.list) == 0 {
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if it.pos > len(it.list) {
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return false
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}
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// If the current value satisfies, then return.
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if it.list[it.pos-1] >= x {
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return true
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}
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// Do binary search between current position and end.
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i := sort.Search(len(it.list), func(i int) bool {
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return it.list[i] >= x
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})
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if i < len(it.list) {
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it.cur = it.list[i]
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it.list = it.list[i+1:]
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return true
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}
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it.list = nil
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return false
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it.pos = sort.Search(len(it.list[it.pos-1:]), func(i int) bool {
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return it.list[i+it.pos-1] >= x
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}) + it.pos
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return it.pos-1 < len(it.list)
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}
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func (it *ListPostings) Err() error {
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@ -1118,3 +1118,147 @@ func TestPostingsWithIndexHeap(t *testing.T) {
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require.Equal(t, storage.SeriesRef(25), node.p.At())
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})
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}
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func TestListPostings(t *testing.T) {
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t.Run("empty list", func(t *testing.T) {
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p := NewListPostings(nil)
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require.False(t, p.Next())
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require.False(t, p.Seek(10))
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require.False(t, p.Next())
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require.NoError(t, p.Err())
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})
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t.Run("one posting", func(t *testing.T) {
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t.Run("next", func(t *testing.T) {
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p := NewListPostings([]storage.SeriesRef{10})
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require.True(t, p.Next())
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require.Equal(t, storage.SeriesRef(10), p.At())
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require.False(t, p.Next())
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require.NoError(t, p.Err())
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})
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t.Run("seek less", func(t *testing.T) {
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p := NewListPostings([]storage.SeriesRef{10})
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require.True(t, p.Seek(5))
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require.Equal(t, storage.SeriesRef(10), p.At())
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require.True(t, p.Seek(5))
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require.Equal(t, storage.SeriesRef(10), p.At())
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require.False(t, p.Next())
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require.NoError(t, p.Err())
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})
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t.Run("seek equal", func(t *testing.T) {
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p := NewListPostings([]storage.SeriesRef{10})
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require.True(t, p.Seek(10))
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require.Equal(t, storage.SeriesRef(10), p.At())
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require.False(t, p.Next())
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require.NoError(t, p.Err())
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})
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t.Run("seek more", func(t *testing.T) {
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p := NewListPostings([]storage.SeriesRef{10})
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require.False(t, p.Seek(15))
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require.False(t, p.Next())
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require.NoError(t, p.Err())
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})
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t.Run("seek after next", func(t *testing.T) {
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p := NewListPostings([]storage.SeriesRef{10})
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require.True(t, p.Next())
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require.False(t, p.Seek(15))
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require.False(t, p.Next())
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require.NoError(t, p.Err())
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})
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})
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t.Run("multiple postings", func(t *testing.T) {
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t.Run("next", func(t *testing.T) {
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p := NewListPostings([]storage.SeriesRef{10, 20})
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require.True(t, p.Next())
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require.Equal(t, storage.SeriesRef(10), p.At())
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require.True(t, p.Next())
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require.Equal(t, storage.SeriesRef(20), p.At())
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require.False(t, p.Next())
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require.NoError(t, p.Err())
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})
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t.Run("seek", func(t *testing.T) {
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p := NewListPostings([]storage.SeriesRef{10, 20})
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require.True(t, p.Seek(5))
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require.Equal(t, storage.SeriesRef(10), p.At())
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require.True(t, p.Seek(5))
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require.Equal(t, storage.SeriesRef(10), p.At())
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require.True(t, p.Seek(10))
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require.Equal(t, storage.SeriesRef(10), p.At())
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require.True(t, p.Next())
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require.Equal(t, storage.SeriesRef(20), p.At())
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require.True(t, p.Seek(10))
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require.Equal(t, storage.SeriesRef(20), p.At())
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require.True(t, p.Seek(20))
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require.Equal(t, storage.SeriesRef(20), p.At())
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require.False(t, p.Next())
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require.NoError(t, p.Err())
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})
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t.Run("seek lest than last", func(t *testing.T) {
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p := NewListPostings([]storage.SeriesRef{10, 20, 30, 40, 50})
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require.True(t, p.Seek(45))
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require.Equal(t, storage.SeriesRef(50), p.At())
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require.False(t, p.Next())
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})
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t.Run("seek exactly last", func(t *testing.T) {
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p := NewListPostings([]storage.SeriesRef{10, 20, 30, 40, 50})
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require.True(t, p.Seek(50))
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require.Equal(t, storage.SeriesRef(50), p.At())
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require.False(t, p.Next())
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})
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t.Run("seek more than last", func(t *testing.T) {
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p := NewListPostings([]storage.SeriesRef{10, 20, 30, 40, 50})
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require.False(t, p.Seek(60))
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require.False(t, p.Next())
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})
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})
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t.Run("seek", func(t *testing.T) {
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for _, c := range []int{2, 8, 9, 10} {
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t.Run(fmt.Sprintf("count=%d", c), func(t *testing.T) {
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list := make([]storage.SeriesRef, c)
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for i := 0; i < c; i++ {
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list[i] = storage.SeriesRef(i * 10)
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}
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t.Run("all one by one", func(t *testing.T) {
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p := NewListPostings(list)
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for i := 0; i < c; i++ {
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require.True(t, p.Seek(storage.SeriesRef(i*10)))
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require.Equal(t, storage.SeriesRef(i*10), p.At())
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}
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require.False(t, p.Seek(storage.SeriesRef(c*10)))
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})
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t.Run("each one", func(t *testing.T) {
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for _, ref := range list {
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p := NewListPostings(list)
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require.True(t, p.Seek(ref))
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require.Equal(t, ref, p.At())
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}
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})
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})
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}
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})
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}
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func BenchmarkListPostings(b *testing.B) {
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const maxCount = 1e6
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input := make([]storage.SeriesRef, maxCount)
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for i := 0; i < maxCount; i++ {
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input[i] = storage.SeriesRef(i << 2)
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}
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for _, count := range []int{100, 1e3, 10e3, 100e3, maxCount} {
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b.Run(fmt.Sprintf("count=%d", count), func(b *testing.B) {
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for i := 0; i < b.N; i++ {
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p := NewListPostings(input[:count])
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var sum storage.SeriesRef
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for p.Next() {
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sum += p.At()
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}
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require.NotZero(b, sum)
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}
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})
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}
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}
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