Improving performance

If you run hogs, you'll get a rough idea of which processes are using the most CPU time.

For example:

$ hogs -n -% 5
PID             NAME  MSEC  PIDS SYSTEM
1                     1315   53%    43%
6          devb-eide   593   24%    19%
54358061        make   206    8%     6%

1                     2026   83%    67%
6          devb-eide   294   12%     9%

1                     2391   75%    79%
6          devb-eide   335   10%    11%
54624301   htmlindex   249    7%     8%

1                     1004   24%    33%
54624301   htmlindex  2959   71%    98%

54624301   htmlindex  4156   96%   138%

54624301   htmlindex  4225   96%   140%

54624301   htmlindex  4162   96%   138%

1                       71   35%     2%
6          devb-eide    75   37%     2%

1                     3002   97%   100%

Let's look at this output. The first iteration indicates that process 1 is using 53% of the CPU. Process 1 is always the process manager, procnto. In this case, it's the idle thread that's using most of the CPU. The entry for devb-eide reflects disk I/O. The make utility is also using the CPU.

In the second iteration, procnto and devb-eide use most of the CPU, but the next few iterations show that htmlindex (a program that creates the keyword index for our online documentation) gets up to 96% of the CPU. When htmlindex finishes running, procnto and devb-eide use the CPU while the HTML files are written. Eventually, procnto—including the idle thread—gets almost all of the CPU.

You might be alarmed that htmlindex takes up to 96% of the CPU, but it's actually a good thing: if you're running only one program, it should get most of the CPU time.

If your system is running several processes at once, hogs could be more useful. It can tell you which of the processes is using the most CPU, and then you could adjust the priorities to favor the threads that are most important. (Remember that in QNX Neutrino, priorities are a property of threads, not of processes.) For more information, see “Priorities” in the Using the Command Line chapter.

Here are some other tips to help you improve your system's performance:

• You can use pidin to get information about the processes that are running on your system. For example, you can get the arguments used when starting the process, the state of the process's threads, and the memory that the process is using.
• The number of threads doesn't effect system reaction time as much as the number of threads at a given priority. The key to performing realtime operations properly is to set up your realtime threads with the priorities required to ensure the system response that you need.