RE: [Cobertura-devel] Performance Issues - cobertura.ser

[Mark D. <Mar...@sa...>]

Cobertura should only read/write the cobertura.ser file once for each =
JVM you run.  The file is accessed via some static methods and =
variables.  The first time coverage data is accessed by the instrumented =
classes, the cobertura.ser file is read in and lingers in memory.  The =
file is flushed back to the disk when the JVM exits.

So reading/writing cobertura.ser probably isn't slowing things down too =
much (unless you're starting a whole bunch of JVMs, but that has its own =
performance problems...)  I'm sure there are things that could be done =
to improve the speed of the instrumented classes, but I haven't had a =
chance to delve into the wide world of Java profiling.

Patches are always welcome :-)
-Mark=20

> -----Original Message-----
> From: cob...@li...=20
> [mailto:cob...@li...] On=20
> Behalf Of Nathan Johns
> Sent: Thursday, June 09, 2005 9:37 PM
> To: cob...@li...
> Subject: [Cobertura-devel] Performance Issues - cobertura.ser
>=20
> Hi,
>=20
> It appears to me, though I haven't looked at the code, that every time
> the cobertura.ser file is touched by a test for instrumentation the
> entire file is read in, updated and then written back to disk.  This
> seems to be a hug performance hit when compared to running the test
> without instrumentation.  (in our case about 6-7 times slower, on a
> build that take 15 minutes without instrumentation this makes it a
> very long build cycle.)
>=20
> Would it perhaps make more sense to append instrumentation data to the
> cobertura.ser file (may need to be done a different way if
> cobertura.ser is a serialized object(s)) and then process all this
> data at reporting time to aggregate it into class statistics?
>=20
> In other words for each test, when it reads in cobertura.ser and
> writes it, it creates its own data either appended or in a separate
> file, and these are all then merged at reporting time.  This would
> reduce disk access and speed up the testing phase and move some of the
> overhead to when the reporting is done.
>=20
> I suppose one possibility is to make use of different cobertura.ser
> files for each module and merge them at the end?  Would appreciate any
> comments you might have.
>=20
> Nathan Johns
>=20
>=20
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