pkg/profilestore: Reduce allocs in writeSeries

[marselester]

Potentially it's possible to reduce allocs in ProfileColumnStore.writeSeries if it's possible to reuse a slice of labels (I followed the call stack and didn't find any concurrent access, but I might be missing something).

# new
BenchmarkProfileColumnStoreWriteSeries-12  5725592  197.7 ns/op  120 B/op  5 allocs/op
# old
BenchmarkProfileColumnStoreWriteSeries-12  4249389  259.8 ns/op  184 B/op  7 allocs/op

new

(pprof) list writeS
Total: 1.26GB
ROUTINE ======================== github.com/parca-dev/parca/pkg/profilestore.(*ProfileColumnStore).writeSeries
  655.02MB   762.02MB (flat, cum) 59.16% of Total
         .          .    105:}
         .          .    106:
         .          .    107:func (s *ProfileColumnStore) writeSeries(ctx context.Context, req *profilestorepb.WriteRawRequest) error {
         .          .    108:	ingester := parcacol.NewIngester(
         .          .    109:		s.logger,
         .      107MB    110:		parcacol.NewNormalizer(s.metastore),
         .          .    111:		s.table,
         .          .    112:		s.schema,
         .          .    113:		s.bufferPool,
         .          .    114:	)
         .          .    115:
         .          .    116:	ls := make(labels.Labels, 0)
         .          .    117:	for _, series := range req.Series {
         .          .    118:		ls = ls[:0]
         .          .    119:		for _, l := range series.Labels.Labels {
         .          .    120:			if valid := model.LabelName(l.Name).IsValid(); !valid {
         .          .    121:				return status.Errorf(codes.InvalidArgument, "invalid label name: %v", l.Name)
         .          .    122:			}
         .          .    123:
  215.51MB   215.51MB    124:			ls = append(ls, labels.Label{
         .          .    125:				Name:  l.Name,
         .          .    126:				Value: l.Value,
         .          .    127:			})
         .          .    128:		}
         .          .    129:
         .          .    130:		// Must ensure label-set is sorted and HasDuplicateLabelNames also required a sorted label-set
  439.51MB   439.51MB    131:		sort.Sort(ls)
         .          .    132:		if name, has := ls.HasDuplicateLabelNames(); has {
         .          .    133:			return status.Errorf(codes.InvalidArgument, "duplicate label names: %v", name)
         .          .    134:		}
         .          .    135:
         .          .    136:		for _, sample := range series.Samples {

old

(pprof) list writeS
Total: 1.43GB
ROUTINE ======================== github.com/parca-dev/parca/pkg/profilestore.(*ProfileColumnStore).writeSeries
  859.52MB   941.52MB (flat, cum) 64.23% of Total
         .          .    105:}
         .          .    106:
         .          .    107:func (s *ProfileColumnStore) writeSeries(ctx context.Context, req *profilestorepb.WriteRawRequest) error {
         .          .    108:	ingester := parcacol.NewIngester(
         .          .    109:		s.logger,
         .       82MB    110:		parcacol.NewNormalizer(s.metastore),
         .          .    111:		s.table,
         .          .    112:		s.schema,
         .          .    113:		s.bufferPool,
         .          .    114:	)
         .          .    115:
         .          .    116:	for _, series := range req.Series {
  508.02MB   508.02MB    117:		ls := make(labels.Labels, 0, len(series.Labels.Labels))
         .          .    118:		for _, l := range series.Labels.Labels {
         .          .    119:			if valid := model.LabelName(l.Name).IsValid(); !valid {
         .          .    120:				return status.Errorf(codes.InvalidArgument, "invalid label name: %v", l.Name)
         .          .    121:			}
         .          .    122:
         .          .    123:			ls = append(ls, labels.Label{
         .          .    124:				Name:  l.Name,
         .          .    125:				Value: l.Value,
         .          .    126:			})
         .          .    127:		}
         .          .    128:
         .          .    129:		// Must ensure label-set is sorted and HasDuplicateLabelNames also required a sorted label-set
  351.51MB   351.51MB    130:		sort.Sort(ls)
         .          .    131:		if name, has := ls.HasDuplicateLabelNames(); has {
         .          .    132:			return status.Errorf(codes.InvalidArgument, "duplicate label names: %v", name)
         .          .    133:		}
         .          .    134:
         .          .    135:		for _, sample := range series.Samples {

[brancz]

Nice find! lgtm