How can I tell how much my system is swapping?

Question

Is there a good way to see how much my system (for example how frequently, how much swap space it is using each time/ on average) is using the swap space during various tasks?

Answer 1

You can use sar -B 1 to get a realtime view of this information (change 1 to the update interval you want).

The output looks like this:

08:11:54 PM  pgpgin/s pgpgout/s   fault/s  majflt/s  pgfree/s pgscank/s pgscand/s pgsteal/s    %vmeff
08:11:55 PM      0.00      0.00     24.00      0.00     57.00      0.00      0.00      0.00      0.00
08:11:56 PM      0.00      0.00     23.53      0.00     53.92      0.00      0.00      0.00      0.00
08:11:57 PM      0.00      0.00     16.00      0.00     53.00      0.00      0.00      0.00      0.00

• pgpgin/s - Total number of kilobytes the system paged in from disk per second.

• pgpgout/s - Total number of kilobytes the system paged out to disk per second.

• fault/s - Number of page faults (major + minor) made by the system per second. This is not a count of page faults that generate I/O, because some page faults can be resolved without I/O.

• majflt/s - Number of major faults the system has made per second, those which have required loading a memory page from disk.

• pgfree/s - Number of pages placed on the free list by the system per second.

• pgscank/s - Number of pages scanned by the kswapd daemon per second.

• pgscand/s - Number of pages scanned directly per second.

• pgsteal/s - Number of pages the system has reclaimed from cache (pagecache and swapcache) per second to satisfy its memory demands.