hbase-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Elliott Clark (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10320) Avoid ArrayList.iterator() in tight loops
Date Tue, 14 Jan 2014 01:29:52 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10320?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13870265#comment-13870265
] 

Elliott Clark commented on HBASE-10320:
---------------------------------------

I pushed a new version of the benchmark code.  Here's the results:
https://microbenchmarks.appspot.com/runs/55cd6335-b892-4d4f-83dc-97a4cd2a7e69

> Avoid ArrayList.iterator() in tight loops
> -----------------------------------------
>
>                 Key: HBASE-10320
>                 URL: https://issues.apache.org/jira/browse/HBASE-10320
>             Project: HBase
>          Issue Type: Bug
>          Components: Performance
>            Reporter: Lars Hofhansl
>         Attachments: 10320-0.94-v2.txt, 10320-0.94-v3.txt, 10320-0.94.txt
>
>
> I noticed that in a profiler (sampler) run ScanQueryMatcher.setRow(...) showed up at
all.
> In turns out that the expensive part is iterating over the columns in ExcplicitColumnTracker.reset().
I did some microbenchmarks and found that
> {code}
> private ArrayList<X> l;
> ...
> for (int i=0; i<l.size(); i++) {
>    X = l.get(i);
>    ...
> }
> {code}
> Is twice as fast as:
> {code}
> private ArrayList<X> l;
> ...
> for (X : l) {
>    ...
> }
> {code}
> The indexed version asymptotically approaches the iterator version, but even at 1m entries
it is still faster.
> In my tight loop scans this provides for a 5% performance improvement overall when the
ExcplicitColumnTracker is used.
> Edit:
> {code}
> private X[] l;
> ...
> for (int i=0; i<l.length; i++) {
>    X = l[i];
>    ...
> }
> {code}
> Is even better. Apparently the JVM can even save the boundary check in each iteration.



--
This message was sent by Atlassian JIRA
(v6.1.5#6160)

Mime
View raw message