A. Sundararajan's Weblog

4 ways to view Java heap histogram with Mustang

With Mustang (Java SE 6), there are atleast 4 ways to get histogram of Java heap:

1. Using jmap

   
       jmap -histo <pid-of-java-process>
   
   

2. Using -XX:+PrintClassHistogram option when starting the java application. With this option, whenever SIGQUIT signal is sent (pressing Ctrl-\ on Unix, Ctrl-Break on Windows), heap histogram is printed.
3. Using jmap tool to dump heap dump and viewing the same using jhat

   
       jmap -dump:format=b,file=heap.bin <pid-of-java-process>
       jhat heap.bin
   
   

   When jhat is started, visit the URL "http://localhost:7000/" and click on "Show heap histogram" link to view the histogram.
4. Using DTrace with Mustang. The following D-script accumulates count and total size in aggregates -- which can be printed on END probe. This script uses object-alloc probe. More details on Mustang built-in DTrace probes can be found in Keith's blog

   
       hotspot$1:::object-alloc {
           self->str_ptr = (char*) copyin(arg1, arg2+1);
           self->str_ptr[arg2] = '\0';
           self->classname = (string) self->str_ptr;
           @allocs_count[self->classname] = count();
           @allocs_size[self->classname] = sum(arg3);
       }
   

( Feb 17 2006, 03:39:07 PM IST ) Permalink Comments [1] | | | | |