Re: [Gc] Problems with GC performance using gcj

Ivan Maidanski ivmai at
Sat Jan 8 23:33:49 PST 2011

Hi Ben,

Fri, 7 Jan 2011 10:16:56 -0500 "Ben Keppler" <bkeppler at>:
> NOTE:  This question was also posted on the gcj mailing list.
> We are using gcj for a time sensitive application.  One of the
> requirements of the application is that messages be transmitted within a
> 60ms timeframe.  Unfortunately, the Boehm GC used in gcj is not
> generational and thus every collection is of the "stop the world"
> variety.  We are observing (using "GC_PRINT_STATS") regular collections
> that stop the world for periods in the 400ms range.  This is a problem
> for us.
> The comments I have found on the "incremental" setting for the Boehm GC
> indicate that it doesn't work with gcj, so that would not appear to be
> an option.  My question is, are there other GC options (perhaps a
> generational garbage collector) available for gcj?  My research has
> revealed none other than TinyGC, an option that would exacerbate rather
> than relieve our problems.  Alternatively, are there settings on the
> Boehm GC that might relieve our problems?  I would appreciate any
> information you could provide.

AFAIK, there is no alternative to BDWGC for gcj. So, the only thing for you (unless you decide to switch to some real-time JVM) is to play with GC tuning.
I haven't seen that comments about incremental mode in gcj, but the true is that gcj uses previous BoehmGC major release and I don't know whether the bugs fixed in the current BoehmGC release has been also fixed in libgc of gcj.

You are right about TinyGC which I wrote to be a replacement for BoehmGC - my intention was small code (as well as the possibility to quickly replace BoehmGC for testing purposes) not speed.


> Ben Keppler, Software Engineer
> E-mail: bkeppler at * Voice: 828.684.7474 * Fax: 828.684.7874
> <> 

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