prometheus/pkg/labels
Oleg Zaytsev 280eaf33f0
Use global string map for MatchType.String() (#9237)
* Use global string map for MatchType.String()

We were unnecessarily creating a new map for each call of String().

This is a 10x improvement in MatchType.String() performance in time,
from 53ns to 4ns on my i7 laptop, and I guess that this method is being
called quite often so why throw out the resources.

I was surprised that benchmark says that there are no allocations made
in the old version.

I also tries using `//go:generate stringer` and the result is even
better, at about 2.8ns, but having to keep the generated code updated
isn't worth the change (at least it's bigger than a small change I was
intended to do)

Benchmark comparison:

    name \ time/op    old          global_map  stringer
    MatchType_String  53.6ns ± 1%  4.1ns ± 1%  2.8ns ± 1%

    name \ alloc/op   old          global_map  stringer
    MatchType_String   0.00B       0.00B       0.00B

    name \ allocs/op  old          global_map  stringer
    MatchType_String    0.00        0.00        0.00

Old benchmark:

    goos: darwin
    goarch: amd64
    pkg: github.com/prometheus/prometheus/pkg/labels
    cpu: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
    BenchmarkMatchType_String 	21766578	        54.36 ns/op	       0 B/op	       0 allocs/op
    BenchmarkMatchType_String 	21742339	        53.28 ns/op	       0 B/op	       0 allocs/op
    BenchmarkMatchType_String 	21985470	        53.37 ns/op	       0 B/op	       0 allocs/op
    BenchmarkMatchType_String 	21676282	        53.50 ns/op	       0 B/op	       0 allocs/op
    BenchmarkMatchType_String 	22075573	        53.33 ns/op	       0 B/op	       0 allocs/op
    PASS
    ok  	github.com/prometheus/prometheus/pkg/labels	6.252s

New with global map:

    goos: darwin
    goarch: amd64
    pkg: github.com/prometheus/prometheus/pkg/labels
    cpu: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
    BenchmarkMatchType_String 	283412692	         4.129 ns/op	       0 B/op	       0 allocs/op
    BenchmarkMatchType_String 	294859941	         4.091 ns/op	       0 B/op	       0 allocs/op
    BenchmarkMatchType_String 	295750158	         4.113 ns/op	       0 B/op	       0 allocs/op
    BenchmarkMatchType_String 	282827982	         4.072 ns/op	       0 B/op	       0 allocs/op
    BenchmarkMatchType_String 	292942393	         4.047 ns/op	       0 B/op	       0 allocs/op
    PASS
    ok  	github.com/prometheus/prometheus/pkg/labels	8.238s

Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>

* Use array instead of map

Since MatchType is an iota type, we can safely use an array here.

This solution is even better:

    name \ time/op    old          global_map  stringer    array
    MatchType_String  53.6ns ± 1%  4.1ns ± 1%  2.8ns ± 1%  1.0ns ± 1%

    name \ alloc/op   old          global_map  stringer    array
    MatchType_String   0.00B       0.00B       0.00B       0.00B

    name \ allocs/op  old          global_map  stringer    array
    MatchType_String    0.00        0.00        0.00        0.00

Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>

* Benchmark all MatchType values

Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com>
Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>

* Use constants for limits

Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>

Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com>

Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com>
2021-08-24 11:26:16 +05:30
..
labels.go labels: Reduce allocated memory and latency of Hash method; Added tests. (#8025) 2020-10-15 11:31:28 +01:00
labels_test.go Update Makefile.common 2021-04-13 09:33:45 +02:00
matcher.go Use global string map for MatchType.String() (#9237) 2021-08-24 11:26:16 +05:30
matcher_test.go Use global string map for MatchType.String() (#9237) 2021-08-24 11:26:16 +05:30
regexp.go Don't do literal regex matching optimisation when case insensitive. (#8013) 2020-10-06 13:16:26 +01:00
regexp_test.go Testify: move to require (#8122) 2020-10-29 09:43:23 +00:00
test_utils.go Port tsdb to use pkg/labels. (#6326) 2019-11-18 11:53:33 -08:00