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tsdb: more efficient sorting of postings read from WAL at startup (#10500)

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* tsdb: avoid slice-to-interface allocation in EnsureOrder

This is pulling the `seriesRefSlice` out of the loop, so the compiler
doesn't allocate a new one on the heap every time.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

* tsdb: use pointer type in Pool for EnsureOrder

As noted by staticcheck, Pool prefers the objects in the pool to have
pointer type. This is a little more fiddly to code, but avoids
allocation of a wrapper object every time a slice is put into the pool.

Removed a comment that said fixing this has a performance penalty: not
borne out by benchmarks.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
This commit is contained in:
Bryan Boreham 2022-03-30 10:40:19 +01:00 committed by GitHub
parent 3e4bd4d913
commit 2c1be4df7b
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1 changed files with 14 additions and 11 deletions
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25
tsdb/index/postings.go
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@ -39,7 +39,8 @@ const ensureOrderBatchSize = 1024
// ensureOrderBatchPool is a pool used to recycle batches passed to workers in MemPostings.EnsureOrder(). // ensureOrderBatchPool is a pool used to recycle batches passed to workers in MemPostings.EnsureOrder().
var ensureOrderBatchPool = sync.Pool{ var ensureOrderBatchPool = sync.Pool{
New: func() interface{} { New: func() interface{} {
return make([][]storage.SeriesRef, 0, ensureOrderBatchSize) x := make([][]storage.SeriesRef, 0, ensureOrderBatchSize)
return &x // Return pointer type as preferred by Pool.
}, },
} }
@ -231,39 +232,41 @@ func (p *MemPostings) EnsureOrder() {
} }
n := runtime.GOMAXPROCS(0) n := runtime.GOMAXPROCS(0)
workc := make(chan [][]storage.SeriesRef) workc := make(chan *[][]storage.SeriesRef)
var wg sync.WaitGroup var wg sync.WaitGroup
wg.Add(n) wg.Add(n)
for i := 0; i < n; i++ { for i := 0; i < n; i++ {
go func() { go func() {
var sortable seriesRefSlice
for job := range workc { for job := range workc {
for _, l := range job { for _, l := range *job {
sort.Sort(seriesRefSlice(l)) sortable = l
sort.Sort(&sortable)
} }
job = job[:0] *job = (*job)[:0]
ensureOrderBatchPool.Put(job) //nolint:staticcheck // Ignore SA6002 safe to ignore and actually fixing it has some performance penalty. ensureOrderBatchPool.Put(job)
} }
wg.Done() wg.Done()
}() }()
} }
nextJob := ensureOrderBatchPool.Get().([][]storage.SeriesRef) nextJob := ensureOrderBatchPool.Get().(*[][]storage.SeriesRef)
for _, e := range p.m { for _, e := range p.m {
for _, l := range e { for _, l := range e {
nextJob = append(nextJob, l) *nextJob = append(*nextJob, l)
if len(nextJob) >= ensureOrderBatchSize { if len(*nextJob) >= ensureOrderBatchSize {
workc <- nextJob workc <- nextJob
nextJob = ensureOrderBatchPool.Get().([][]storage.SeriesRef) nextJob = ensureOrderBatchPool.Get().(*[][]storage.SeriesRef)
} }
} }
} }
// If the last job was partially filled, we need to push it to workers too. // If the last job was partially filled, we need to push it to workers too.
if len(nextJob) > 0 { if len(*nextJob) > 0 {
workc <- nextJob workc <- nextJob
} }