RFR: JDK-8171294: Slow compilation with long classpaths under JDK 9

Maurizio Cimadamore maurizio.cimadamore at oracle.com
Wed Jan 25 11:29:25 UTC 2017

On 25/01/17 10:27, Claes Redestad wrote:
> Hi,
> this might be a pre-existing issue, but doesn't this need to take Multi-
> Release JARs into account and walk the (most) appropriate subtree?
My understanding (Jan corrects me if I'm wrong) is that javac delegates 
MR-jar questions to the underlying nio file system. So, given the cache 
is implemented using a nio file walker, the code should be already doing 
the appropriate thing?

> Thanks!
> /Claes
> On 2017-01-24 15:35, Jan Lahoda wrote:
>> Hi,
>> As reported:
>> https://bugs.openjdk.java.net/browse/JDK-8171294
>> http://mail.openjdk.java.net/pipermail/compiler-dev/2016-December/010596.html 
>> javac has a problem with compiling with many jars on classpath. The
>> problem is twofold:
>> a) there is JavacFileManager.ArchiveContainer.pathCache, and this cache
>> keeps entries not only for path that are in the given archive/jar, but
>> also for those that are not in it, which may consume too much memory
>> b) when listing a package, for each archive/jar, an equivalent of
>> Files.exists(Path.resolve(String)) is done, which takes some time, and
>> this is repeated a lot of times (and most of the time, the package does
>> not exist in the given jar).
>> The proposed patch is basically Maurizio's patch that lists packages on
>> opening and then can quickly decide if a given archive/jar contains the
>> given package or not. The biggest change from the original patch is that
>> the packages are computed immediately when the ArchiveContainer is
>> created, as opposed to compute them lazily. The reason is that the
>> Containers are created lazily, and are used immediately after being
>> created.
>> Webrev:
>> http://cr.openjdk.java.net/~jlahoda/8171294/webrev.00/
>> How does this look?
>> Thanks,
>>     Jan

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