Jarreorder and classlists

David Holmes david.holmes at oracle.com
Tue Aug 20 01:54:06 UTC 2013

Hi Erik,

Adding in hotspot-runtime-dev.

There is a lot of history here and I'm not sure who remembers all the 
details - if anyone. There are existing open bugs to re-assess the 
utility of the jarreorder (7032729) and to update the classlists (8005688).


On 20/08/2013 1:17 AM, Erik Joelsson wrote:
> Hello,
> I wonder if anyone knows more about the jarreorder tool and why we use it?
> As I understand it, we have precalculated classlists for each platform
> (most likely outdated) and the tool is used to make sure those classes
> end up in a specific order, last in rt.jar. I assume this is some kind
> of startup time optimization.
> I got some help from Claes in the performance team and did a quick run
> of a startup and footprint benchmark, comparing a build with the rt.jar
> reordered as normal and one where I simply turned off this feature and
> let the files end up in the default order. Our preliminary findings show
> that any difference between the two is negligible. Before we declare it
> useless, we might need to test with freshly generated classlists? Does
> anyone know how to generate them? Is there some other benefit of this
> that I might have missed?
> I would like to propose removing jarreorder to simplify the build. This
> would also enable faster incremental builds of the images target, by not
> having to rebuild the whole rt.jar every time.
> /Erik

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