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From "Xiao-Feng Li" <xiaofeng...@gmail.com>
Subject Re: [VM] On-demand class library parsing is ready to commit
Date Fri, 26 Dec 2008 01:14:15 GMT
On Fri, Dec 26, 2008 at 12:49 AM, Alexei Fedotov
<alexei.fedotov@gmail.com> wrote:
> Aleksey,
> I like your conclusion.
>
> Wenlong,
> I'm trying to understand the real life value of the "abstract" startup
> time metric you've suggested. Does Harmony with your patch load
> swing.jar for a server application? Do I understand that loading
> happens, though it happens later compared to VM without your patch? I
> believe that the proper design of delayed loading should answer "no"
> to this question.

I checked the patch, and I found the answer is indeed "No" as you expected.

Thanks,
xiaofeng

> In other words, I appreciate if you describe which real use cases are
> improved by this patch.
> Thanks!

> On Thu, Dec 25, 2008 at 7:29 PM, Aleksey Shipilev
> <aleksey.shipilev@gmail.com> wrote:
>> Ok, here's the catch.
>>
>> bootclasspath.properties is the SortedSet<JARfile>, which enumerates
>> the JARs available for bootclassloader. The set of such the JARs is
>> really stable because modular decomposition of classlib is stable.
>> That's why nobody bothers with automatic generation of it: it only
>> should be updated when new JAR file arrives.
>> Modulelibrarymapping.properties is different on this point, it's the
>> Map<PackageName,JARfile>, which should be updated each time the new
>> *package* is introduced. I'm not talking about java.* packages
>> (they're standardized), rather about org.apache.harmony.*.
>>
>> Automatic generation of this property file gives two advantages:
>>  1. Error-prone. Prevent yourself from hand-messing with mapping and
>> getting spurious ClassNotFoundException. BTW, what's the behaviour in
>> case the mapping is wrong?
>>  2. "Researchful". There're lot of guys around who enjoys the
>> modularity of Harmony classlib and eventually they might want to split
>> the packages even deeper, into smaller pieces. Then automatic
>> generation would enable them to quickly roll-in and experiment with
>> different package layouts and their impact on performance. They could
>> use ordinary bootclasspath.properties, but your feature wouldn't be
>> used by them then ;)
>>
>> That's merely a housekeeping procedure. I believe that anything which
>> could be done more than once, eventually would be done more than once.
>> Hence it should be automated. You say that the file was generated from
>> manifests of JARs, so is it hard to just tie the same tool into DRLVM
>> build process?
>>
>> As for DRLVM-specific, my opinion that this is because the patch:
>>  a. breaks the compatibility of classlib (you change
>> bootclasspath.properties, right?) with other VMs.
>>  b. treated in DRLVM classloader only.
>>
>> Of course eventually this feature might be used by others, but IMO we
>> should be careful about other guys who use the same classlib. I'd
>> rather wait for some incubation on DRLVM side first.
>>
>> Thanks,
>> Aleksey.
>>
>> On Thu, Dec 25, 2008 at 6:18 PM, Wenlong Li <wenlong@gmail.com> wrote:
>>> I see. In fact, my file doesn't need track change at the class
>>> granularity. Instead, it only needs know package info provided in the
>>> manifest file.  When class is added to a library, do we need change
>>> the manifest as well?
>>>
>>> btw, I guess there is a mis-understanding: my modulelibrarymapping
>>> file only records package info provided by manfiest in each module. It
>>> doesn't relate to each class.
>>>
>>> thx,
>>> Wenlong
>>>
>>> On Thu, Dec 25, 2008 at 10:55 PM, Pavel Pervov <pmcfirst@gmail.com> wrote:
>>>> Classes are added to class library from time to time. I'm not sure how
>>>> it can be possible to track these changes manually.
>>>>
>>>> WBR,
>>>>    Pavel.
>>>>
>>>>
>>>> On Thu, Dec 25, 2008 at 5:09 PM, Wenlong Li <wenlong@gmail.com> wrote:
>>>>> Sorry, one more question: bootclasspath.properties is classlib
>>>>> specific file, why we could not make a vm specific file manually? Just
>>>>> curious to know the possible reason. :)
>>>>>
>>>>> thx,
>>>>> Wenlong
>>>>>
>>>>> On Thu, Dec 25, 2008 at 10:00 PM, Pavel Pervov <pmcfirst@gmail.com>
wrote:
>>>>>> If this would be VM-side automatically produced configuration file...
>>>>>>
>>>>>> WBR,
>>>>>>    Pavel.
>>>>>>
>>>>>> On Thu, Dec 25, 2008 at 4:58 PM, Wenlong Li <wenlong@gmail.com>
wrote:
>>>>>>> btw, because adding new module is rare case, manually modifying
the
>>>>>>> bootclasspath.properties is not an issue?
>>>>>>>
>>>>>>> If so, can I conclude adding another property file with same
update
>>>>>>> frequency as bootclasspath would be fine as well?
>>>>>>>
>>>>>>> Pls kindly correct me if my understanding is wrong.
>>>>>>>
>>>>>>> On Thu, Dec 25, 2008 at 9:05 PM, Pavel Pervov <pmcfirst@gmail.com>
wrote:
>>>>>>>> Wenlong,
>>>>>>>>
>>>>>>>> Note, that bootclasspath.properties is only changed on adding
new
>>>>>>>> module. This is pretty rare occasion, I believe.
>>>>>>>>
>>>>>>>> WBR,
>>>>>>>>    Pavel.
>>>>>>>>
>>>>>>>> On Thu, Dec 25, 2008 at 3:48 PM, Wenlong Li <wenlong@gmail.com>
wrote:
>>>>>>>>> Thx for your advice. Alexey.
>>>>>>>>>
>>>>>>>>> Here I have one question: do you know how the bootclasspath.properties
>>>>>>>>> is maintained, manually or automatically?
>>>>>>>>>
>>>>>>>>> Another comment is I would like to treat the patch as
DRLVM specific
>>>>>>>>> optimization, e.g., it targets for improving VM creation
time. So that
>>>>>>>>> is possible to move all updates to DRLVM part to eliminate
potential
>>>>>>>>> modularity and compatibility problem.
>>>>>>>>>
>>>>>>>>> thx,
>>>>>>>>> Wenlong
>>>>>>>>>
>>>>>>>>> On Thu, Dec 25, 2008 at 5:32 PM, Aleksey Shipilev
>>>>>>>>> <aleksey.shipilev@gmail.com> wrote:
>>>>>>>>>> Hi, Wenlong.
>>>>>>>>>>
>>>>>>>>>> On Thu, Dec 25, 2008 at 11:49 AM, Wenlong Li <wenlong@gmail.com>
wrote:
>>>>>>>>>>> btw, Alexey, Let's go back to discuss whether
there is a need to
>>>>>>>>>>> include this feature in Harmony, given 17% performance
gain in Linux
>>>>>>>>>>> when using your methodology. For windows test,
I will double check the
>>>>>>>>>>> backgroud process as you pointed out.
>>>>>>>>>>
>>>>>>>>>> My opinion was already expressed after I had finished
the tests from
>>>>>>>>>> my side: the boost can be achieved in specific conditions,
so whether
>>>>>>>>>> it's worth including into Harmony really depends
on how much mess the
>>>>>>>>>> patch would introduce besides the "performance boost".
From what I
>>>>>>>>>> see, the patch obliges the maintainer to maintain
the correct mapping
>>>>>>>>>> between jars and Java packages. This new feature
is also spread
>>>>>>>>>> between Classlib and VM, but it seems like DRLVM
specific. In this
>>>>>>>>>> case I would rather stay without the patch.
>>>>>>>>>>
>>>>>>>>>> Personally (if I'll be committer) I would accept
the patch with two
>>>>>>>>>> serious modifications:
>>>>>>>>>>  1. Stay within DRLVM, do not introduce this feature
into Classlib,
>>>>>>>>>> get the thing tested and evolved on DRLVM side. Otherwise
it might
>>>>>>>>>> break the compatibility with other VMs.
>>>>>>>>>>  2. Make the mapping generated automatically (during
build process?)
>>>>>>>>>> to free the burden for maintainers.
>>>>>>>>>>
>>>>>>>>>> Thanks,
>>>>>>>>>> Aleksey.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
>
>
> --
> С уважением,
> Алексей Федотов,
> ЗАО «Телеком Экспресс»
>



-- 
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