I have thought about this in the past. The problem is that there's no way to know what settings the JVM will use (or supports) without launching the JVM. I have toyed with the idea of doing a separate execution of 'java' just to get information on the JVM, either on every startup (for just base JVM info it should be cheap) or once when installing e.g. jruby-launcher.
We also need a better way to specify appropriate "profiles" of settings across JVM versions and vendors. For example, the flags we specify for Hotspot like permgen sizes, stack sizes, etc may not be right (or supported) on other JVMs. A perfect example is -client, unsupported on J9 and a no-op on JRockit. Anyone have ideas for how we could do this? Is jruby-launcher the right place, perhaps? - Charlie On Thu, Dec 22, 2011 at 2:11 PM, Rob Heittman <rob.heitt...@solertium.com> wrote: > JVM ergonomics can default to a very small (64Mb) max heap on 32-bit > desktop-class systems; at least older JVMs certainly used to. That's not > enough to do very much at all. > > It would be nice to just yield to the JVM's ergonomics when it is doing > something useful, like the allocations 1.5 and up have applied to > server-class systems. These would often provide for a *larger* heap that > we're discussing allocating here. I have no idea how one would detect the > ergonomics the JVM is using, though. > > On Thu, Dec 22, 2011 at 2:59 PM, Uwe Kubosch <u...@kubosch.no> wrote: >> >> On 2011-12-20, at 07:19, Charles Oliver Nutter wrote: >> >> > I was thinking of bumping to 1GB. >> > >> > A 32-bit JVM can't go higher than a 4GB process space, and typically >> > you don't go above 2GB heap there in case there's a lot of native >> > memory that might push it close to the 32-bit process limit. So I >> > think we'd be safest halving that and doing 1GB, which would be enough >> > for the vast majority of uses, but not so large it would commonly >> > exceed available memory on a typical desktop or server. >> >> >> Why do we need to set the max heap size differently than the JVM default? >> Because JRuby applications need more heap than other Java apps? >> >> If we need to explicitly set the heap size, what about setting it to >> double of the standard JVM setting? >> >> We run lots of different apps on JRuby, and they all have different Xmx >> settings. 512MB fits many Rails apps, but for many background jobs we use >> half that, and for many Rails apps we use much more. >> >> If we cannot adjust to the JVM default settings, I think 512MB on 32-bit >> and 1GB on 64-bit would be good all-round settings. >> >> -- >> Uwe Kubosch >> u...@kubosch.no >> http://kubosch.no/ >> >> >> >> >> >> >> >> --------------------------------------------------------------------- >> To unsubscribe from this list, please visit: >> >> http://xircles.codehaus.org/manage_email >> >> > --------------------------------------------------------------------- To unsubscribe from this list, please visit: http://xircles.codehaus.org/manage_email
