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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5068) Investigate increased CPU usage on client after introduction of UTF-8 CcsidManager
Date Thu, 28 Apr 2011 10:28:03 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5068?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13026241#comment-13026241
] 

Knut Anders Hatlen commented on DERBY-5068:
-------------------------------------------

One transaction in the single-record select client results in the following calls to Utf8CcsidManager
methods:

- 8 calls to getByteLength()

- 3 calls to convertFromJavaString(String,byte[],int,Agent)

Both of these methods create an intermediate object (getByteLength() a byte array, convertFromJavaString()
a String) that's thrown away, whereas EbcdicCcsid doesn't do that. Perhaps it's worthwhile
to hand-code the UTF-8 encoding in these two methods to avoid having to create the intermediate
objects. Or if we don't want to maintain code that does UTF-8 encoding ourselves: assume that
all characters are ASCII and only fall back to using intermediate objects if a non-ASCII character
is found.

I'll run a quick experiment on the machines where I see this issue.

> Investigate increased CPU usage on client after introduction of UTF-8 CcsidManager
> ----------------------------------------------------------------------------------
>
>                 Key: DERBY-5068
>                 URL: https://issues.apache.org/jira/browse/DERBY-5068
>             Project: Derby
>          Issue Type: Task
>    Affects Versions: 10.7.1.1
>            Reporter: Knut Anders Hatlen
>
> While looking at the performance graphs for the single-record select test during the
last year - http://home.online.no/~olmsan/derby/perf/select_1y.html - I noticed that there
was a significant increase (10-20%) in CPU usage per transaction on the client early in October
2010. To be precise, the increase seems to have happened between revision 1004381 and revision
1004794. In that period, there were three commits: two related to DERBY-4757, and one related
to DERBY-4825 (tests only).
> We should try to find out what's causing the increased CPU usage and see if there's some
way to reduce it.

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