RFR: 6988220: java.lang.ObjectName use of String.intern() causes major performance issues at scale

[Dmytro Sheyko]

Hi,

Though "compareTo" tends to be less efficient than "equals", it offers better type safety.

When we (mistakenly!) compare objects of different type, "equals" silently accepts parameter of wrong type,
but returns false. Comparison with "compareTo" is rejected by compiler.

Consider,

String string = ...
Date date = ...

if (string.equals(date)) { // always false
}

if (string.compareTo(date) == 0) { // compilation error
}

Regards,
Dmytro

> Date: Thu, 23 Feb 2012 10:58:47 -0500
> Subject: Re: RFR: 6988220: java.lang.ObjectName use of String.intern() causes	major performance issues at scale
> From: vitalyd at gmail.com
> To: frederic.parain at oracle.com
> CC: serviceability-dev at openjdk.java.net; core-libs-dev at openjdk.java.net
> 
> Hi Frederic,
> 
> Just curious - why are you checking string equality via compareTo() instead
> of equals()?
> 
> Thanks
> 
> Sent from my phone
> On Feb 23, 2012 10:37 AM, "Frederic Parain" <frederic.parain at oracle.com>
> wrote:
> 
> > This a simple fix to solve CR 6988220:
> > http://bugs.sun.com/**bugdatabase/view_bug.do?bug_**id=6988220<http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6988220>
> >
> > The use of String.intern() in the ObjectName class prevents
> > the class the scale well when more than 20K ObjectNames are
> > managed. The fix simply removes the use of String.intern(),
> > and uses regular String instead. The Object.equals() method
> > is modified too to make a regular String comparison. The
> > complexity of this method now depends on the length of
> > the ObjectName's canonical name, and is not impacted any
> > more by the number of ObjectName instances being handled.
> >
> > The Webrev:
> > http://cr.openjdk.java.net/~**fparain/6988220/webrev.00/<http://cr.openjdk.java.net/~fparain/6988220/webrev.00/>
> >
> > I've tested this fix with the jdk_lang and jdk_management
> > test suites.
> >
> > Thanks,
> >
> > Fred
> >
> > --
> > Frederic Parain - Oracle
> > Grenoble Engineering Center - France
> > Phone: +33 4 76 18 81 17
> > Email: Frederic.Parain at oracle.com
> >
> >