[jira] Commented: (HARMONY-5025) [classlib][nio] make AbstractSelectableChannel.containsValidKeys() a little bit faster

["Alexey Varlamov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HARMONY-5025?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12537833 ] 

Alexey Varlamov commented on HARMONY-5025:
------------------------------------------

Heh, then reverse cycle should be a bit more faster ;)

> [classlib][nio] make AbstractSelectableChannel.containsValidKeys() a little bit faster
> --------------------------------------------------------------------------------------
>
>                 Key: HARMONY-5025
>                 URL: https://issues.apache.org/jira/browse/HARMONY-5025
>             Project: Harmony
>          Issue Type: Improvement
>          Components: Classlib
>            Reporter: Sergey Dmitriev
>            Assignee: Tim Ellison
>         Attachments: cvk.patch
>
>
> Some time ago I've found a piece of code in NIO which can be simply improved.
> AbstractSelectableChannel.java:
>     /**
>      * Returns true if the keyList contains at least 1 valid key and false otherwise.
>      */
>     private synchronized boolean containsValidKeys() {
> -         for (Iterator<SelectionKey> iter = keyList.iterator(); iter.hasNext();) {
> -             SelectionKey key = iter.next();
> +        for (int i=0; i<keyList.size(); i++) {
> +            SelectionKey key = keyList.get(i);
>             if (key != null && key.isValid()) {
>                 return true;
>             }
>         }
>     }
> Just don't create an Iterator here. Indeed no big deal, but it would be just pity to loose this discovery. :)
> I even created the mini test to demonstrate the benefit of my patch (approx 10%).
> {guy@nowhere:~/tmp} cat cvk.java
> import java.io.*;
> import java.nio.channels.*;
> // cvk: containsValidKeys()
> public class cvk {
>     static int numOfIters = 10;
>     static int numOfConfigures = 10*1000*1000;
>     public static void main(String[] args) throws Exception {
>         ServerSocketChannel ssc = ServerSocketChannel.open();
>         for (int i=0; i<numOfIters; i++) {
>             long millis = System.currentTimeMillis();
>             for (int j=0; j<numOfConfigures; j++) {
>                 ssc.configureBlocking(false);
>                 ssc.configureBlocking(true);
>             }
>             System.out.println(System.currentTimeMillis() - millis);
>         }
>     }
> }
> {guy@nowhere:~/tmp} ~/harmony.29sep.my.nocvk/bin/java -Xem:server cvk
> 7049
> 6149
> 6134
> 6125
> 6140
> 6139
> 6131
> 6142
> 6148
> 6200
> {guy@nowhere:~/tmp} ~/harmony.29sep.my.cvk/bin/java -Xem:server cvk
> 5769
> 5499
> 5491
> 5497
> 5483
> 5474
> 5466
> 5470
> 5453
> 5478

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