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https://issues.apache.org/jira/browse/IO-468?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Thomas Neidhart updated IO-468:
-------------------------------
Attachment: micro-benchmark.zip
I took the time to re-write my benchmark using jmh.
The results are somehow similar, but more accurate (Score is in ns/operation):
{noformat}
Benchmark (length) Mode Cnt Score Error
Units
IOUtilsBenchmark.copyFixedArray 100 avgt 20 255.966 ± 1.580
ns/op
IOUtilsBenchmark.copyFixedArray 1000 avgt 20 349.467 ± 3.376
ns/op
IOUtilsBenchmark.copyFixedArray 10000 avgt 20 1735.641 ± 47.352
ns/op
IOUtilsBenchmark.copyFixedArray 100000 avgt 20 20991.194 ± 253.866
ns/op
IOUtilsBenchmark.copyFixedArray 1000000 avgt 20 253168.783 ± 35859.304
ns/op
IOUtilsBenchmark.copyNormal 100 avgt 20 2039.469 ± 60.206
ns/op
IOUtilsBenchmark.copyNormal 1000 avgt 20 2210.150 ± 69.705
ns/op
IOUtilsBenchmark.copyNormal 10000 avgt 20 3467.281 ± 76.302
ns/op
IOUtilsBenchmark.copyNormal 100000 avgt 20 23033.581 ± 323.091
ns/op
IOUtilsBenchmark.copyNormal 1000000 avgt 20 251249.970 ± 23086.488
ns/op
IOUtilsBenchmark.copyThreadLocal 100 avgt 20 263.559 ± 0.985
ns/op
IOUtilsBenchmark.copyThreadLocal 1000 avgt 20 359.917 ± 4.831
ns/op
IOUtilsBenchmark.copyThreadLocal 10000 avgt 20 1795.665 ± 43.034
ns/op
IOUtilsBenchmark.copyThreadLocal 100000 avgt 20 20777.176 ± 206.086
ns/op
IOUtilsBenchmark.copyThreadLocal 1000000 avgt 20 251769.416 ± 19318.802
ns/op
{noformat}
To run the benchmark do the following on the command line:
{noformat}
mvn clean install
java -jar target/benchmarks.jar
{noformat}
> Avoid allocating memory for method internal buffers, use threadlocal memory
> instead
> -----------------------------------------------------------------------------------
>
> Key: IO-468
> URL: https://issues.apache.org/jira/browse/IO-468
> Project: Commons IO
> Issue Type: Improvement
> Components: Utilities
> Affects Versions: 2.4
> Environment: all environments
> Reporter: Bernd Hopp
> Priority: Minor
> Labels: newbie, performance
> Fix For: 2.5
>
> Attachments: PerfTest.java, micro-benchmark.zip,
> monitoring_with_threadlocals.png, monitoring_without_threadlocals.png,
> performancetest.ods, performancetest_weakreference.ods
>
> Original Estimate: 12h
> Remaining Estimate: 12h
>
> In a lot of places, we allocate new buffers dynamically via new byte[]. This
> is a performance drawback since many of these allocations could be avoided if
> we would use threadlocal buffers that can be reused. For example, consider
> the following code from IOUtils.java, ln 2177:
> return copyLarge(input, output, inputOffset, length, new
> byte[DEFAULT_BUFFER_SIZE]);
> This code allocates new memory for every copy-process, that is not used
> outside of the method and could easily and safely reused, as long as is is
> thread-local. So instead of allocating new memory, a new utility-class could
> provide a thread-local bytearray like this:
> byte[] buffer = ThreadLocalByteArray.ofSize(DEFAULT_BUFFER_SIZE);
> return copyLarge(input, output, inputOffset, length, buffer);
> I have not measured the performance-benefits yet, but I would expect them to
> be significant, especially when the streams itself are not the performance
> bottleneck.
> Git PR is at https://github.com/apache/commons-io/pull/6/files
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