Posts Tagged ‘performance’

One accurate measurement is worth a thousand expert opinions

Monday, April 6th, 2009

“One accurate measurement is worth a thousand expert opinions” – Adm Grace Murray Hopper ( Dec 9 1906 to Jan 1 1992)

Measurement is the most important aspect of Performance Engineering. There is no place for guess work in performance engineering. Measuring tools are the most important tools in a Performance Engineer’s tool set.

In one of the projects I was involved in, the second day of my job I was validating the solution for a high throughput. Everything was going fine till the performance test started throwing lot of errors. The solution involved around 15 servers. I had set up monitoring of resources on all the 15 servers. First thing I did was look up the resource utilization of all the servers. There was one server where the memory utilization kept on growing. I narrowed down to the process which was growing in memory. The graph of the memory utilization for the process showed a linear growth, it went up as high as 1GB and then the process terminated. This graph was proof enough to show the developer that the process had a big memory leak. This was fixed within a day and solution was ready for further testing.

Performance engineering requires lot of discipline and a methodical approach. Lot of times when we come across problems we tend to start giving expert opinions, start guessing where the problem might be or start looking at the code. One needs to take a scientific approach. One has to look at the facts, start with resource utilization and then narrow down to looking at logs, timestamps, database metrics, application server metrics, compare with historical benchmarks etc.

Check this out. The very first computer bug.

Open Source Performance Testing

Friday, March 20th, 2009

Open Source has taken a center stage in the development world. It is a community effort which can not stopped. Either you ride it or get run over by it.

One area where open source has not yet made a big dent is in test automation and performance testing.
This area is still dominated by commercial tools. Most of the commercial tools available for automation and performance testing are extremely expensive. The leading tools from HP (QTP, Loadrunner) and Borland ( Silk Performer, Silk Test) come with a huge price tag.

I used to be a developer before I jumped into Performance Testing back in 1998. That time I was still not able to let go of my development skills. For the first Performance Testing assignment I had built a load testing tool using MS VC++ ( are we not talking of open source here?), the GUI for it is shown below. This was perfect for me. It suited all my needs for driving the load on the server. I had other scripts to automate monitoring, logging and analyzing the results ( see the tool image below).  Well right around then the company I used to work for, decided on standardizing the tool set and we settled on Silk Performer ( then a product of Segue). Using the tool was good for my resume value and it did have lots more bells and whistles.

Using gdb to find memory leaks in HP Unix

Sunday, March 1st, 2009

The following gdb commands are used to setup memory leak detection in C++ programs:
set heap-check leaks on
set heap-check free on
set heap-check bounds on
set heap-check scramble on

To show the leak the following command is used:

(gdb) info leaks

To view a particular leak from a list of leaks detected use the following:

(gdb) info leak  <leak number> ( leak number is the relevant number from the leak)

It is very important that program be linked with shared library to use heap profiling.

The following example is using xscAppAdapter as a C++ program to demonstrate memory leak detection.