[jboss-dev] Further profling: Where should I focus?

[David M. Lloyd]

On 01/05/2010 11:22 AM, David M. Lloyd wrote:
> On 01/05/2010 11:18 AM, Bill Burke wrote:
>>
>>
>> David M. Lloyd wrote:
>>> On 01/05/2010 10:40 AM, Bill Burke wrote:
>>>>
>>>> Ales Justin wrote:
>>>>> Perhaps this can be solved by custom (+ temp) deployer,
>>>>> which would create capabilities from those exports,
>>>>> but would just say import-all for imports.
>>>>>
>>>> No shit shirlock...Especially when thats what is being done now.
>>>>
>>>> Again, optimizing this algorithm doesn't matter if jars/directories are
>>>> being browsed.
>>>
>>> What do you mean by "browsed"? If you're going to access any file in a
>>> JAR, you need to scan the (unordered) ZIP directory anyway. Better to do
>>> it one time and cache it so files can be looked up on an O(1) basis. And
>>> once you've done that, why not use that data for other purposes?
>>>
>>
>> A simple test of using ZipInputStream vs. URLClassLoader to find a
>> resource within jacorb.jar.
>>
>> ZipInputStream: 256ms.
>> URLClassLoader: 5ms.
>>
>> URLClasLoader is obviously using some other mechanism to find things.
>
> Uh yeah using ZIS is a really bad idea for reasons covered several
> months ago. URLClassLoader is opening a ZipFile.

To spell it out, a ZIP file is divided up into many sections.  The 
directory is at the end of the zip file.  Using ZIS iterates the sections 
corresponding to files - which is NOT guaranteed to work right - and thus 
passes over the entire file in the process.  Using ZipFile simply reads the 
directory which is at the END of the zip file and is stored in a much more 
compact fashion - less I/O, more speed.

Anyway this has all been covered, benchmarked, and fixed by VFS3.

- DML