Hi Claes,
Here's the pre-post-patch comparison:
import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;
import java.util.concurrent.TimeUnit;
import java.util.jar.Attributes;
@BenchmarkMode(Mode.AverageTime)
@Warmup(iterations = 5)
@Measurement(iterations = 10)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Fork(1)
@State(Scope.Thread)
public class JarAttributesBench {
/*
pre-patch:
Benchmark Mode Cnt Score Error Units
JarAttributesBench.buildAttributes avgt 10 814.876 ± 10.300 ns/op
JarAttributesBench.lookupAttributes avgt 10 728.400 ± 4.005 ns/op
post-patch:
Benchmark Mode Cnt Score Error Units
JarAttributesBench.buildAttributes avgt 10 949.266 ± 8.422 ns/op
JarAttributesBench.lookupAttributes avgt 10 890.683 ± 6.651 ns/op
*/
private static final String[] keys = {
"Manifest-Version", "Created-By", "Signature-Version",
"Class-Path", "Main-Class"
};
private Attributes attributes;
@Setup(Level.Trial)
public void setup() {
attributes = buildAttributes();
}
@Benchmark
public Attributes buildAttributes() {
Attributes attr = new Attributes();
for (String key : keys) {
attr.putValue(key, key);
}
return attr;
}
@Benchmark
public void lookupAttributes(Blackhole bh) {
Attributes attr = attributes;
for (String key : keys) {
bh.consume(attr.getValue(key));
}
}
}
... so nothing drastic.
On 03/09/2016 02:03 PM, Claes Redestad wrote:
On 2016-03-09 13:17, Peter Levart wrote:
When digging through old history to try to find out why
java.util.jar.Attributes
was ever using ASCIICaseInsensitiveComparator, it was not clear that
performance was the motivation.
I guess looking-up a manifest attribute is not a performance critical
operation, you are right.
Could this be an old startup optimization, since first call to
String.toLowerCase/toUpperCase will initialize and pull in
java.util.Locale and friends? If so it's probably not effective any more.
Could be, yes.
Coincidentally - due to a recent regression - we're currently spending
quite a bit of time parsing manifests of all jar files on the
classpath, making ASCIICaseInsensitiveComparator show up prominently
in some startup profiles.
/Claes
Regards, Peter
