A number of opensolaris communities have asked their members for feedback, and the list of technologies they would like to see added in the future. The storage community received a ton of feedback when they asked the community for the list of features they would like to have added to opensolaris, and this feedback was recently posted to the genunix wiki. If there are features you are interested in that don’t appear on the list, I would highly recommend adding them. There are so many cool things underway (Comstar, CIFS client and server, NPIV support, pNFS, better remote replication, etc.) in the storage community, and it’s awesome to see the storage project leaders reaching out to the community to get their ideas!
While doing a bit of research tonight I came across a reference to mod_substitute. This nifty module allows you to substitute text in the HTTP request body, which provides an easy way to do things similar to the following:
<Location /private>
AddOutputFilterByType SUBSTITUTE text/html
Substitute s/SECRET/XXXXX/ni
</Location>
I digs me some Apache!
I gave a presentation last night on debugging Java performance problems. I got a couple of requests to post links to the performance analysis tools I discussed, so here you go:
Garbage collection log visualization utility
Garbage collection visualization utility
Monitoring garbage collection with jstat
Observing object allocation with DTrace
I would like to thank everyone for attending, and hope to see ya’ll at a future meeting!
While reading through some old notes this weekend, I came across a page I created eons ago about managing Solaris packages. If you want to find out the file modes, the user and group ownership and the package a file belongs to, you can run the pkgchk utility with the “-l” and “-p” options and the name of a file to check:
$ pkgchk -l -p /usr/sfw/bin/snmpget
Pathname: /usr/sfw/bin/snmpget
Type: regular file
Expected mode: 0755
Expected owner: root
Expected group: bin
Expected file size (bytes): 20372
Expected sum(1) of contents: 48443
Expected last modification: Sep 20 17:41:36 2007
Referenced by the following packages:
SUNWsmcmd
Current status: installed
Pkgchk is a nifty utility!
The Java SDK comes with a number of tools and JVM options that can be used to analyze the performance of the Java runtime. One extremely useful tool is the heap profiler agent, which provides facilities to profile memory usage, CPU utilization and lock contention. To load the profiler agent to profile CPU utilization, you can add the “-agentlib:hprof=cpu=times” option to your java command line:
$ java -Xms256m -Xmx256m -verbose:gc -agentlib:hprof=cpu=times App
Once loaded, the agent will use byte code injection (BCI) to instrument each method’s entry and return points. This allows the agent to measure the number of times each method was called, the time spent in each method, and the call chain that led to the method being invoked. To utilize the agent to it’s full potential, you will need to exercise the application while the agent is active. Once the runtime has been exercised, you can hit cntrl+C to stop the process. This will cause the agent to write the data it has collected to the file java.hprof.txt, which can be viewed with your favorite pager or editor:
$ more java.hprof.txt
CPU TIME (ms) BEGIN (total = 40712194) Mon Jan 21 19:23:12 2008
rank self accum count trace method
1 38.52% 38.52% 1036273 301143 java.util.Random.next
2 19.57% 58.09% 518136 301144 java.util.Random.nextDouble
3 11.87% 69.96% 518136 301145 java.lang.Math.random
4 11.05% 81.01% 1036274 301141 java.util.concurrent.atomic.AtomicLong.get
5 10.53% 91.54% 1036273 301142 java.util.concurrent.atomic.AtomicLong.compareAndSet
6 8.14% 99.68% 259068 301146 TestMain.foo
7 0.05% 99.73% 1 300969 java.security.Permissions.add
8 0.04% 99.77% 1 301106 java.lang.Class.privateGetDeclaredFields
9 0.03% 99.79% 1 301138 java.util.Random.
10 0.02% 99.81% 2 300908 java.io.FilePermission$1.run
11 0.01% 99.82% 1 301283 java.lang.ThreadGroup.remove
12 0.01% 99.83% 1 300820 sun.net.www.protocol.file.Handler.createFileURLConnection
......
The java.hprof.txt file contains the number of times each method was invoked, as well as the amount of CPU time (as a percentage) that was spent in each method. To see how a method was called, you can search the profiler output for the trace identifier that is listed along side the profiling data. This will produce a Java stack trace similar to the following that shows how a given method was invoked:
TRACE 301143:
java.util.Random.next(Random.java:Unknown line)
java.util.Random.nextDouble(Random.java:Unknown line)
java.lang.Math.random(Math.java:Unknown line)
TestMain.foo(TestMain.java:Unknown line)
The BCI approach introduces a fair amount of overhead to the Java runtime. In cases were the overhead is hindering testing, you can use the agent’s “cpu=samples” option instead. This will cause the agent to sample the runtime environment at periodic intervals to see which methods are executing. While this approach is not as accurate as the BCI approach, it provides a good set of results with less runtime overhead. The java profiling agent is incredibly useful, and just one of the vast number of tools that are available to profile Java applications.