Re: Howto: Profiling GCJ code?

[Ian Rogers <ian.rogers@manchester.ac.uk>]

Hi,

I just wanted to add a note that to improve the nio performance for
the DaCapo benchmark suite certain special cases were optimized in
Jikes RVM's usage of VMChannel from Classpath (LGPL source visible at
[1]). The FileSystem object within JikesRVM just provides a means to
access open/close/read/write calls without the overhead of JNI (in
much the same way as CNI does for GCJ). There exists CNI channel code,
if nio is a performance problem I believe something can be learnt from
the RVM code base as I don't believe NIO is a performance issue in the
RVM any more.

Regards,
Ian

[1] http://git.codehaus.org/gitweb.cgi?p=mrp.git;a=blob;f=libraryInterface/GNUClasspath/LGPL/src/gnu/java/nio/VMChannel.java;h=8edf32bbf1d630c34b8db317c25376ba85e2a930;hb=HEAD
--
Metacircular Research Platform ( http://mrp.codehaus.org/ ), supports
the development of optimized metacircular Virtual Machines in Java on
Linux, OS/X and Windows.

2009/6/19 Bryce McKinlay <bmckinlay@gmail.com>:
> The tool of choice for libgcj profiling is oprofile:
> http://oprofile.sourceforge.net/
>
> This should give you reasonably accurate, low-overhead profiling
> without having to recompile anything, and even a call graph though
> both the java and C/C++ code.
>
> It doesn't surprise me that libgcj's java.nio is slow. Hotspot VMs can
> also optimize nio code in ways that gcj can't.
>
> Bryce
>
>
> On Fri, Jun 19, 2009 at 9:52 AM, Patrick Schäfer<ps@ekse.de> wrote:
>> Hi,
>>
>> I am trying to run a server based on apache mina (java.nio) and jna for
>> native library access. The program runs just fine under jdk 1.5. But there
>> is a massive performance breakdown using gcj. The program basically polls a
>> Posix Message Queue every 500ms using JNA (JNI). This causes 5% cpu load on
>> jdk but the load goes up to 100% using gcj.
>>
>> Is there any profiling tool which can be easily installed and applied to the
>> native code?
>>
>> I read about profiling gcj applications on your faq. There are 3 tools
>> mentioned. To my understanding gprof can't be applied due to missing
>> multithreading support and it requires the program to exit main before
>> writing any profiling information. The later is not easy when using a
>> network server. cprof seems to be quite outdated (there has been no realease
>> within the last years) and trying to "make" it, fails with several errors. I
>> don't know about sprof, but I couldn't find much information about it on the
>> internet.
>>
>> Thank you for any hints about current multithreading gcj (gcc) profilers
>>
>> Patrick
>>
>