On Thu, May 2, 2019 at 10:59 AM Tomo Suzuki <suzt...@google.com.invalid> wrote:
> Gary, > I didn't find ConstantUtf8.getCachedInstance > <https://github.com/apache/commons-bcel/blob/master/src/main/java/org/apache/bcel/classfile/ConstantUtf8.java#L94> > is used in BCEL (latest 6.3.1). I tried my custom ConstantUtf8 modification > to leverage getCachedInstance method and it worked well: > > Before > > Without getCachedInstance, my tool created 2,6 million ConstantUtf8 > instances (before failing OutOfMemoryError: GC overhead limit exceeded) to > check ~200 jar files > [image: 2644k_constantutf8_without_getCachedInstance.png] > > > After > > With getCachedInstance, my tool created just 0.6 million ConstantUtf8 > instances. It didn't throw the OutOfMemoryError. > [image: 621k_constantutf8_with_getCachedInstance.png] > > My modification was to use getCachedInstance for > ConstantUtf8.getInstance(DataInput) > <https://github.com/apache/commons-bcel/blob/master/src/main/java/org/apache/bcel/classfile/ConstantUtf8.java#L123> > . > > > Do you know why ConstantUtf8.getCachedInstance is unused? > I do not. Gary > > Regards, > Tomo > > > > On Wed, May 1, 2019 at 7:02 PM Gary Gregory <garydgreg...@gmail.com> > wrote: > >> On Wed, May 1, 2019 at 6:37 PM Tomo Suzuki <suzt...@google.com.invalid> >> wrote: >> >> > Gary, >> > That’s right. I missed it. I think I just need to find a way to leverage >> > the getCachedInstance method. Thank you for quick response. >> > >> >> YW. Please let us know your outcome. >> >> Gary >> >> >> > >> > On Wed, May 1, 2019 at 18:00 Gary Gregory <garydgreg...@gmail.com> >> wrote: >> > >> > > Why not use getCachedInstance() ? >> > > >> > > Gary >> > > >> > > On Wed, May 1, 2019 at 5:20 PM Tomo Suzuki <suzt...@google.com.invalid >> > >> > > wrote: >> > > >> > > > Hi BCEL developers, >> > > > >> > > > We use BCEL library to inspect Java class. Thank you for the great >> > > library. >> > > > >> > > > When our tool checks classes in ~200 jar files, it creates more >> than 2 >> > > > million BCEL ConstantUtf8 instances. I suspect many of them share >> the >> > > same >> > > > values such as "java.lang.String". >> > > > >> > > > [image: many_constant_utf8.png] >> > > > >> > > > Given this observation, I got an idea to to reuse ConstantUtf8 with >> > same >> > > > value to save memory footprint. Because ConstantUtf8 is constant, >> > sharing >> > > > the instances across classes should not cause a problem. Note that >> BCEL >> > > is >> > > > not designed thread-safe (doc >> > > > <https://commons.apache.org/proper/commons-bcel/faq.html>). >> > > > >> > > > If this is a good idea, I'm thinking to make a pull request around >> > BCEL's >> > > > ConstantUtf8.getInstance method: >> > > > >> > > > >> > > >> > >> https://github.com/apache/commons-bcel/blob/master/src/main/java/org/apache/bcel/classfile/ConstantUtf8.java#L116 >> > > > >> > > > Does anybody have any thought? >> > > > >> > > > -- >> > > > Regards, >> > > > Tomo >> > > > >> > > >> > -- >> > Regards, >> > Tomo >> > >> > > > -- > Regards, > Tomo >
