Jarreorder and classlists

[Erik Joelsson]

On 2013-10-01 15:05, David Holmes wrote:
> On 1/10/2013 8:30 PM, Erik Joelsson wrote:
>> Hello again,
>>
>> I have now regenerated the classlists @b107 and run new comparisons. To
>> me it looks like the differences are essentially non existant between
>> new and old classlists and in the previous comparison we saw no
>> difference between random order and old classlists.
>>
>> It's very possible that it has an impact on cold starts, as Staffan
>> suggests, but we have no way (that I know of) of measuring that, and is
>> that really a valid requirement if we can't measure it?
>
> There are startup benchmarks as part of our internal benchmarking 
> suites. They are what are used to measure this AFAIK.
Those are the very tests I used, with guidance from the performance team.

/Erik
>
> David
>
>> /Erik
>>
>> On 2013-08-20 03:54, David Holmes wrote:
>>> 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).
>>>
>>> David
>>> ------
>>>
>>> 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 (most likely outdated) and the tool is used to make sure those classes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
>>