schlosna opened a new pull request #352:
URL: https://github.com/apache/httpcomponents-client/pull/352
While analyzing some JFR profiles from a service utilizing a high volume of
async HTTP client requests, I noticed one of the top memory allocations of
`java.text.DecimalFormatSymbols` coming from
`org.apache.hc.client5.http.impl.ExecSupport#getNextExchangeId`, notably due to
use of `String#format`. Given that this seems to be on a hot code path, we can
optimize this code path.
Backtrace:
```
sun.util.locale.provider.DecimalFormatSymbolsProviderImpl.getInstance(Locale)
java.text.DecimalFormatSymbols.getInstance(Locale)
java.util.Formatter.zero()
java.util.Formatter$FormatSpecifier.getZero(Locale)
java.util.Formatter$FormatSpecifier.localizedMagnitude(StringBuilder,
CharSequence, int, Formatter$Flags, int, Locale)
java.util.Formatter$FormatSpecifier.print(long, Locale)
java.util.Formatter$FormatSpecifier.printInteger(Object, Locale)
java.util.Formatter$FormatSpecifier.print(Object, Locale)
java.util.Formatter.format(Locale, String, Object[])
java.util.Formatter.format(String, Object[])
java.lang.String.format(String, Object[])
org.apache.hc.client5.http.impl.ExecSupport.getNextExchangeId()
org.apache.hc.client5.http.impl.classic.InternalHttpClient.doExecute(HttpHost,
ClassicHttpRequest, HttpContext)
org.apache.hc.client5.http.impl.classic.CloseableHttpClient.execute(ClassicHttpRequest,
HttpContext)
org.apache.hc.client5.http.impl.classic.CloseableHttpClient.execute(ClassicHttpRequest)
```
With a hand rolled a method to perform the same functionality of
`String.format("ex-%010d", long)` we see a roughly 20x speed-up in execution
time and ~16x reduction in allocations on a JMH microbenchmark for just this
function (see https://github.com/schlosna/httpclient-format-performance ). This
PR currently only optimizes the hot exchange ID code path and not the endpoint
ID code paths that use similar formatting (see
https://github.com/apache/httpcomponents-client/pull/249 )
Benchmarks all run on 16 core Intel(R) Xeon(R) Platinum 8259CL CPU @ 2.50GHz.
JDK 11.0.13, OpenJDK 64-Bit Server VM, 11.0.13+8-LTS
```
Benchmark Mode Cnt
Score Error Units
FormatBenchmarks.stringFormat avgt 5
674.730 ± 7.821 ns/op
FormatBenchmarks.stringFormat:·gc.alloc.rate avgt 5
852.757 ± 9.814 MB/sec
FormatBenchmarks.stringFormat:·gc.alloc.rate.norm avgt 5
704.000 ± 0.001 B/op
FormatBenchmarks.stringFormat:·gc.churn.G1_Eden_Space avgt 5
862.955 ± 171.696 MB/sec
FormatBenchmarks.stringFormat:·gc.churn.G1_Eden_Space.norm avgt 5
712.471 ± 146.197 B/op
FormatBenchmarks.stringFormat:·gc.churn.G1_Old_Gen avgt 5
0.001 ± 0.002 MB/sec
FormatBenchmarks.stringFormat:·gc.churn.G1_Old_Gen.norm avgt 5
0.001 ± 0.002 B/op
FormatBenchmarks.stringFormat:·gc.count avgt 5
53.000 counts
FormatBenchmarks.stringFormat:·gc.time avgt 5
33.000 ms
FormatBenchmarks.zeroPad avgt 5
38.760 ± 1.082 ns/op
FormatBenchmarks.zeroPad:·gc.alloc.rate avgt 5
1855.680 ± 51.458 MB/sec
FormatBenchmarks.zeroPad:·gc.alloc.rate.norm avgt 5
88.000 ± 0.001 B/op
FormatBenchmarks.zeroPad:·gc.churn.G1_Eden_Space avgt 5
1859.501 ± 202.606 MB/sec
FormatBenchmarks.zeroPad:·gc.churn.G1_Eden_Space.norm avgt 5
88.186 ± 10.045 B/op
FormatBenchmarks.zeroPad:·gc.churn.G1_Old_Gen avgt 5
0.004 ± 0.002 MB/sec
FormatBenchmarks.zeroPad:·gc.churn.G1_Old_Gen.norm avgt 5 ≈
10⁻⁴ B/op
FormatBenchmarks.zeroPad:·gc.count avgt 5
79.000 counts
FormatBenchmarks.zeroPad:·gc.time avgt 5
62.000 ms
```
JDK 15.0.5, OpenJDK 64-Bit Server VM, 15.0.5+3-MTS
```
Benchmark Mode Cnt
Score Error Units
FormatBenchmarks.stringFormat avgt 5
1081.263 ± 50.140 ns/op
FormatBenchmarks.stringFormat:·gc.alloc.rate avgt 5
1094.601 ± 50.204 MB/sec
FormatBenchmarks.stringFormat:·gc.alloc.rate.norm avgt 5
1448.105 ± 0.005 B/op
FormatBenchmarks.stringFormat:·gc.churn.G1_Eden_Space avgt 5
1093.372 ± 0.707 MB/sec
FormatBenchmarks.stringFormat:·gc.churn.G1_Eden_Space.norm avgt 5
1446.645 ± 67.105 B/op
FormatBenchmarks.stringFormat:·gc.churn.G1_Survivor_Space avgt 5
0.004 ± 0.007 MB/sec
FormatBenchmarks.stringFormat:·gc.churn.G1_Survivor_Space.norm avgt 5
0.006 ± 0.009 B/op
FormatBenchmarks.stringFormat:·gc.count avgt 5
55.000 counts
FormatBenchmarks.stringFormat:·gc.time avgt 5
51.000 ms
FormatBenchmarks.zeroPad avgt 5
39.612 ± 1.489 ns/op
FormatBenchmarks.zeroPad:·gc.alloc.rate avgt 5
1815.969 ± 68.124 MB/sec
FormatBenchmarks.zeroPad:·gc.alloc.rate.norm avgt 5
88.006 ± 0.001 B/op
FormatBenchmarks.zeroPad:·gc.churn.G1_Eden_Space avgt 5
1829.120 ± 209.669 MB/sec
FormatBenchmarks.zeroPad:·gc.churn.G1_Eden_Space.norm avgt 5
88.641 ± 9.053 B/op
FormatBenchmarks.zeroPad:·gc.churn.G1_Survivor_Space avgt 5
0.008 ± 0.002 MB/sec
FormatBenchmarks.zeroPad:·gc.churn.G1_Survivor_Space.norm avgt 5
≈ 10⁻³ B/op
FormatBenchmarks.zeroPad:·gc.count avgt 5
92.000 counts
FormatBenchmarks.zeroPad:·gc.time avgt 5
80.000 ms
```
JDK 17.0.1, OpenJDK 64-Bit Server VM, 17.0.1+12-LTS
```
Benchmark Mode Cnt
Score Error Units
FormatBenchmarks.stringFormat avgt 5
871.173 ± 11.990 ns/op
FormatBenchmarks.stringFormat:·gc.alloc.rate avgt 5
1313.506 ± 18.053 MB/sec
FormatBenchmarks.stringFormat:·gc.alloc.rate.norm avgt 5
1400.111 ± 0.011 B/op
FormatBenchmarks.stringFormat:·gc.churn.G1_Eden_Space avgt 5
1314.209 ± 139.635 MB/sec
FormatBenchmarks.stringFormat:·gc.churn.G1_Eden_Space.norm avgt 5
1400.917 ± 157.487 B/op
FormatBenchmarks.stringFormat:·gc.churn.G1_Survivor_Space avgt 5
0.006 ± 0.008 MB/sec
FormatBenchmarks.stringFormat:·gc.churn.G1_Survivor_Space.norm avgt 5
0.006 ± 0.009 B/op
FormatBenchmarks.stringFormat:·gc.count avgt 5
81.000 counts
FormatBenchmarks.stringFormat:·gc.time avgt 5
53.000 ms
FormatBenchmarks.zeroPad avgt 5
41.057 ± 0.172 ns/op
FormatBenchmarks.zeroPad:·gc.alloc.rate avgt 5
1751.849 ± 7.370 MB/sec
FormatBenchmarks.zeroPad:·gc.alloc.rate.norm avgt 5
88.007 ± 0.001 B/op
FormatBenchmarks.zeroPad:·gc.churn.G1_Eden_Space avgt 5
1752.274 ± 171.164 MB/sec
FormatBenchmarks.zeroPad:·gc.churn.G1_Eden_Space.norm avgt 5
88.027 ± 8.268 B/op
FormatBenchmarks.zeroPad:·gc.churn.G1_Survivor_Space avgt 5
0.009 ± 0.005 MB/sec
FormatBenchmarks.zeroPad:·gc.churn.G1_Survivor_Space.norm avgt 5
≈ 10⁻³ B/op
FormatBenchmarks.zeroPad:·gc.count avgt 5
108.000 counts
FormatBenchmarks.zeroPad:·gc.time avgt 5
69.000 ms
```
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