prometheus/pkg
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
..
exemplar Add Exemplar Remote Write support (#8296) 2021-05-06 13:53:52 -07:00
gate Fix exported function comments (#6002) 2019-09-10 14:45:09 +01:00
labels Use global string map for MatchType.String() (#9237) 2021-08-24 11:26:16 +05:30
logging Switched to go-kit/log 2021-06-11 12:28:36 -04:00
modtimevfs *: check that assets are up-to-date (#4731) 2018-11-09 11:31:36 +01:00
pool Testify: move to require (#8122) 2020-10-29 09:43:23 +00:00
relabel Add hashmod relabeling test with hasmod and a newline 2021-03-02 23:01:22 +01:00
rulefmt fixes yamllint errors 2021-06-12 12:47:47 +02:00
runtime Fix golint issues. 2020-03-23 20:38:43 +01:00
textparse Return error on NaN and Inf timestamps for OpenMetrics parser 2021-06-28 20:55:04 -04:00
timestamp '@ <timestamp>' modifier (#8121) 2021-01-20 16:27:39 +05:30
value Fix spelling/typos (#4921) 2018-11-27 17:44:29 +01:00