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https://issues.apache.org/jira/browse/DIRMINA-751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12789718#action_12789718
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Emmanuel Lecharny commented on DIRMINA-751:
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I have applied the fix :
http://svn.apache.org/viewvc?rev=889927&view=rev
Some thoughts :
- we need a real unit test for IoBuffer. It has to be written as a Unit Test,
with no main() method, and an Inner class to be able to test this
normalizeCapacity method
- in MINA 3.0, the IoBuffer class will probably be removed, or refactored, as
we don't really need all this mechanism, but this is more something we should
discuss on the ML.
- the class hierarchy is probably overkilling. We should have a IoBuffer
interface, an AbstractIoBuffer abstract class, move the IoBufferWrapper and
ProxyHandshakeIoBuffer classes to be subclasses of the AbstractIoBuffer class.
- I'm not convinced that using the CachedBuffer brings any speed improvement.
Trying to be smarter than the VM is most certainly a lost of time... IMO, this
class should be removed.
Let's discuss all that on the ML for MINA 3.0 !
> IoBuffer.normalizeCapacity improvement
> --------------------------------------
>
> Key: DIRMINA-751
> URL: https://issues.apache.org/jira/browse/DIRMINA-751
> Project: MINA
> Issue Type: Improvement
> Components: Core
> Affects Versions: 2.0.0-RC1
> Environment: N/A
> Reporter: Bogdan Pistol
> Priority: Minor
> Fix For: 2.0.0-RC2
>
> Attachments: IoBufferTest.java, IoBufferTest.java, patch.txt
>
>
> The technique of computing the minimum power of 2 that is bigger than the
> requestedCapacity in the
> org.apache.mina.core.buffer.IoBuffer.normalizeCapacity() is not optimal.
> The current computation is as follows:
> int newCapacity = 1;
> while ( newCapacity < requestedCapacity ) {
> newCapacity <<= 1;
> if ( newCapacity < 0 ) {
> return Integer.MAX_VALUE;
> }
> }
> The time complexity of this is O(n), where n is the number of bits of the
> requestedCapacity integer, that is log2(requestedCapacity) - maximum 31.
> This creates an unnecessary overhead in some high IoBuffer allocations
> scenarios that are calling IoBuffer.normalizeCapacity() a lot when creating
> IoBuffers. I observed this when benchmarking a MINA server with hprof.
> There is a better solution to this problem than to iterate the bits from 0 to
> log2(requestedCapacity).
> The alternative is to use a binary search technique that has optimal time
> complexity of O(5). Because requestedCapacity is an integer and has a maximum
> of 2^5 (32) bits we can binary search in the set of bits and determine in
> O(5) comparisons the minimum power of 2 that is bigger than the
> requestedCapacity.
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