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lib/model: Optimize jobQueue performance and memory use (#8023) 

By truncating time.Time to an int64 nanosecond count, we lose the
ability to precisely order timestamps before 1678 or after 2262, but we
gain (linux/amd64, Go 1.17.1):

name                      old time/op    new time/op    delta
JobQueuePushPopDone10k-8    2.85ms ± 5%    2.29ms ± 2%  -19.80%  (p=0.000 n=20+18)
JobQueueBump-8              34.0µs ± 1%    29.8µs ± 1%  -12.35%  (p=0.000 n=19+19)

name                      old alloc/op   new alloc/op   delta
JobQueuePushPopDone10k-8    2.56MB ± 0%    1.76MB ± 0%  -31.31%  (p=0.000 n=18+13)

name                      old allocs/op  new allocs/op  delta
JobQueuePushPopDone10k-8      23.0 ± 0%      23.0 ± 0%     ~     (all equal)

Results for BenchmarkJobQueueBump are with the fixed version, which no
longer depends on b.N for the amount of work performed. rand.Rand.Intn
is cheap at ~10ns per iteration.
This commit is contained in:
greatroar 2021-10-29 20:20:46 +02:00 committed by GitHub
parent 296cc1bca2
commit 807a6b1022
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 10 additions and 5 deletions
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7
lib/model/queue.go
View File

@ -23,7 +23,7 @@ type jobQueue struct {
type jobQueueEntry struct {
name string
size int64
modified time.Time
modified int64
}
func newJobQueue() *jobQueue {
@ -34,7 +34,8 @@ func newJobQueue() *jobQueue {
func (q *jobQueue) Push(file string, size int64, modified time.Time) {
q.mut.Lock()
q.queued = append(q.queued, jobQueueEntry{file, size, modified})
// The range of UnixNano covers a range of reasonable timestamps.
q.queued = append(q.queued, jobQueueEntry{file, size, modified.UnixNano()})
q.mut.Unlock()
}
@ -191,5 +192,5 @@ func (q smallestFirst) Swap(a, b int) { q[a], q[b] = q[b], q[a] }
type oldestFirst []jobQueueEntry
func (q oldestFirst) Len() int { return len(q) }
func (q oldestFirst) Less(a, b int) bool { return q[a].modified.Before(q[b].modified) }
func (q oldestFirst) Less(a, b int) bool { return q[a].modified < q[b].modified }
func (q oldestFirst) Swap(a, b int) { q[a], q[b] = q[b], q[a] }

8
lib/model/queue_test.go
View File

@ -8,6 +8,7 @@ package model
import (
"fmt"
"math/rand"
"testing"
"time"
@ -251,16 +252,19 @@ func TestSortByAge(t *testing.T) {
}
func BenchmarkJobQueueBump(b *testing.B) {
files := genFiles(b.N)
files := genFiles(10000)
q := newJobQueue()
for _, f := range files {
q.Push(f.Name, 0, time.Time{})
}
rng := rand.New(rand.NewSource(int64(b.N)))
b.ResetTimer()
for i := 0; i < b.N; i++ {
q.BringToFront(files[i].Name)
r := rng.Intn(len(files))
q.BringToFront(files[r].Name)
}
}