How to calculate the context switches and disk reads that my C program makes

Joohi · 02-05-2012, 11:18 PM

I need to count the total number of context switches and disk reads that a given C program makes. The nearest thing that I could find was vmstat command that monitors the system performance. But it gives out details of all the process that have been executed since boot time, and doesn't give a PID. How do I calculate the required parameters of a program that has already completed execution?

syg00 · 02-06-2012, 12:53 AM

It looks like Mark is planning on adding this (context switch data) to collectl - I'm sure he'll comment shortly.
If you want to track the process yourself, the data is in /proc/<pid>/status (presuming you have the appropriate kernel options selected) - but that data will be lost at process termination unless you do something to save it.

Joohi · 02-08-2012, 03:35 AM

The function - getrusage() can be used, it provides all the required parameters.

markseger · 02-10-2012, 05:05 PM

Indeed mark IS planning on providing context switches by process. The process output has gotten so wide I've decided to make this optional by requesting 'extended' process stats like this, noting that extended stats apply to both top, interactive and playback. This is an example of top, sorted by voluntary context switches:

collectl --top vctx --procopt x

Code:

# TOP PROCESSES sorted by vctx (counters are /sec) 23:04:17
# PID  User     PR  PPID THRD S   VSZ   RSS CP  SysT  UsrT Pct  AccuTime  RKB  WKB VCtx NCtx MajF MinF Command
21171  1333     20 21170    0 S   42M    2M 12  0.01  0.00   1  00:03.83    0    0  309   21    0    0 ssh
21172  1333     20 21170    0 S    4M  584K 12  0.00  0.02   2  00:05.08    0    0  309    0    0    0 gzip
21198  1333     20 21195    0 S    4M  588K  8  0.00  0.02   2  00:04.19    0    0  263    1    0    0 gzip
21047  1333     20 21045    0 S   42M    2M  7  0.01  0.01   2  00:03.26    0    0  262    8    0    0 ssh
21197  1333     20 21195    0 S   42M    2M 20  0.01  0.00   1  00:03.33    0    0  262    2    0    0 ssh
21048  1333     20 21045    0 S    4M  584K  1  0.00  0.02   2  00:04.46    0    0  261    1    0    0 gzip
21071  1333     20 21070    0 S   42M    2M  0  0.01  0.00   1  00:03.30    0    0  261    0    0    0 ssh

I'm planning on pushing a new release next week, just waiting for some feedback from a few folks to make sure I didn't break anything they need.

-mark

syg00 · 02-10-2012, 06:58 PM

Code:

# TOP PROCESSES sorted by vctx (counters are /sec) 23:04:17
# PID  User     PR  PPID THRD S   VSZ   RSS CP  SysT  UsrT Pct  AccuTime  RKB  WKB VCtx NCtx MajF MinF Command
21171  1333     20 21170    0 S   42M    2M 12  0.01  0.00   1  00:03.83    0    0  309   21    0    0 ssh
21172  1333     20 21170    0 S    4M  584K 12  0.00  0.02   2  00:05.08    0    0  309    0    0    0 gzip
21198  1333     20 21195    0 S    4M  588K  8  0.00  0.02   2  00:04.19    0    0  263    1    0    0 gzip
21047  1333     20 21045    0 S   42M    2M  7  0.01  0.01   2  00:03.26    0    0  262    8    0    0 ssh
21197  1333     20 21195    0 S   42M    2M 20  0.01  0.00   1  00:03.33    0    0  262    2    0    0 ssh
21048  1333     20 21045    0 S    4M  584K  1  0.00  0.02   2  00:04.46    0    0  261    1    0    0 gzip
21071  1333     20 21070    0 S   42M    2M  0  0.01  0.00   1  00:03.30    0    0  261    0    0    0 ssh

markseger · 02-11-2012, 07:36 AM

thanks syg00 - I went back and fixed it. I know some websites have an icon to click on to insert the right formatting tags but the only one I found was for QUOTE, so I used that and s/QUOTE/CODE/

-mark

SecretCode · 02-11-2012, 10:41 AM

The icon for "CODE" should be in the quick reply box, but isn't ... this has been requested but I think the plan is not to customise the board further before updating to a new version of vbulletin.

If you "Go Advanced" and get the full reply editor, the code icon is the one with a # symbol.