Order of entries in make/mapfiles/reorder-*

David Holmes david.holmes at oracle.com
Fri Dec 8 23:29:49 UTC 2017

Thanks for the pointers! I had not connected these mapfile/reorder-* 
files directly with the old rt.jar reordering - though I guessed they 
served a similar purpose. As Tim later mentions the strange comments in 
the file do seem to match up to the tests.

As these mapfiles are needed for the build to actually work they can't 
be removed without changing the way the build is done. But it seems 
likely that the order of the entries is no longer relevant.


On 9/12/2017 1:32 AM, Claes Redestad wrote:
> I think the tool to generate these reorder files exist under 
> src/utils/reorder, but looking at
> src/utils/reorder/Makefile it seems to have bit-rotted over the years.. 
> the bootclasspath tricks
> with rt.jar etc likely won't even work today:
> # This Makefile is intended to produce new reordering files for the
> # reordering of jar files and shared libraries.  This is not part of the
> # standard build.  The objects produced by this Makefile must be copied
> # into their standard locations and checked in.
> I'm not sure any of this is relevant in the modular world (as most jar 
> files are now merged
> into lib/modules, which has a separate reordering facility that is 
> automatically generated on
> build and enforced by jlink).
> File a bug to investigate and potentially remove it all?
> /Claes
> On 2017-12-08 10:53, Magnus Ihse Bursie wrote:
>> On 2017-12-08 07:26, David Holmes wrote:
>>> Nobody?
>> I don't know. They existed long time before I started working on the 
>> build system. I believe they were an attempt to optimize the layout 
>> based on some test that ran years and years ago. It's likely that they 
>> do nothing (at best) or worsen performance (at worst).  Very few 
>> libraries has these reorder files any more. If you think you need to 
>> update one, I think a reasonable course of action is to remove it 
>> instead.
>> Maybe Claes can help me confirm my speculation about performance..?
>> /Magnus
>>> On 7/12/2017 8:15 PM, David Holmes wrote:
>>>> I have to add new entries to the mapfiles. How is the order in the 
>>>> reorder-* files determined?
>>>> Thanks,
>>>> David

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