On Fri, 18 Oct 2024 09:31:45 GMT, Eirik Bjørsnøs <[email protected]> wrote:
>> With this change to `ZipFileOpen`:
>>
>> diff --git a/test/micro/org/openjdk/bench/java/util/zip/ZipFileOpen.java
>> b/test/micro/org/openjdk/bench/java/util/zip/ZipFileOpen.java
>> index 4f6ae6373ec..0e22cf7f0ab 100644
>> --- a/test/micro/org/openjdk/bench/java/util/zip/ZipFileOpen.java
>> +++ b/test/micro/org/openjdk/bench/java/util/zip/ZipFileOpen.java
>> @@ -73,6 +73,11 @@ public void beforeRun() throws IOException {
>>
>> ename += entryPrefixes[i % entryPrefixes.length] + "-" + i;
>> zos.putNextEntry(new ZipEntry(ename));
>> + zos.putNextEntry(new ZipEntry("META-INF/versions/9/" +
>> ename));
>> + zos.putNextEntry(new ZipEntry("META-INF/versions/11/" +
>> ename));
>> + zos.putNextEntry(new ZipEntry("META-INF/versions/17/" +
>> ename));
>> + zos.putNextEntry(new ZipEntry("META-INF/versions/21/" +
>> ename));
>> + zos.putNextEntry(new ZipEntry("META-INF/versions/24/" +
>> ename));
>> }
>> }
>> zipFile = tempFile;
>>
>>
>> On that modified `ZipFileOpen` micro,
>> https://github.com/eirbjo/jdk/pull/1 improves over #21489 but still regress
>> compared to the baseline:
>>
>>
>> Benchmark (size) Mode Cnt Score Error
>> Units
>> ZipFileOpen.openCloseZipFile 1024 avgt 15 677386,387 ± 15761,989
>> ns/op # baseline
>> ZipFileOpen.openCloseZipFile 1024 avgt 15 1121127,629 ± 16716,218
>> ns/op # pull/21489, 0.6x
>> ZipFileOpen.openCloseZipFile 1024 avgt 15 968501,630 ± 28761,067
>> ns/op # eirbjo/jdk#1, 0.7x
>>
>>
>> I suspect remaining regression is mostly from the added `String`
>> creation/processing in `initCEN`.
>
>> I suspect remaining regression is mostly from the added `String`
>> creation/processing in `initCEN`.
>
> Yes, there is a cost with the String construction when parsing the name out
> of `META-INF/versions/{name}`
There are a few possible strategies for avoiding that additional parse, since
the effect we're getting at here is to have a quick filter to avoid pointless
lookups and not necessarily an exact mapping.
One is to store the `checkedHash` rather than the full `String`. This gets
`openCloseZipFile` down to ~910000 ns/op. (`checkedHash` very hot in profiles).
There's still a chance for redundant lookups on hash collisions, but this
should be rare.
Another is to store a `BitSet` per name length. This gets `ZipFileOpen` down to
baseline level (~670000 ns/op), but increases chance of having to do redundant
lookups a lot.
Both also improves footprint (not keeping each versioned entry `String` in
memory would be nice).
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/21489#discussion_r1806242792
