Jarreorder and classlists

[Brian Doherty]

On 10/01/2013 08:06 AM, Erik Joelsson wrote:
>
> 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.
>
Refworkload fully supports cold start measurement on all of our
supported platforms; though it's be a while since it's been used,
so there could be some bit rot with some of the setup details.

The issue with cold start is that it takes some system configuration
work to get the benchmarks working. The benchmarks can also be
a bit abusive to your disk drive (because of the numerous reboots
that will happen). So, I would not recommend running them on your
personal machines. Fortunately, the cold start setup is well documented
in refworkload.

Point your browser at the coldstart docs inside a refworkload
distribution or workspace:

file:///path/to/your/refworkload/docs/users_guide/coldstart/index.html
file:///path/to/your/refworkload/docs/users_guide/benchmarks/startup3/index.html

Brian

> /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 (most likely outdated) and the tool is used to make sure those 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
>>>
>