[NTLUG:Discuss] why swap?

[Robert Citek]

On Friday, Sep 10, 2004, at 09:38 US/Central, Stephen Klein wrote:
> I'm not sure why rsync would be running slow, but my experience is 
> that 2.4.X kernels tend to us at least a little swap not matter what 
> the actual memory utilization is.  2.6.X kernels may be similar.
>
> In fact, my machine shows no processes swapped out, yet free shows 
> about 38MB swap in use and 29MB free RAM.
>
> Probably harmless.

I'd like to think so.  Except that when I killed rsync swapping 
stopped.  When I restarted it, things ran smoothly, initially.  But 
when I checked back after about an hour, I noticed swap was being used 
again:

# vmstat 10 7
    procs                      memory      swap          io     system   
    cpu
  r  b  w   swpd   free   buff  cache   si   so    bi    bo   in    cs 
us sy id
  1  1  2  41368  18040 327432 2113644    0    1    22    16   20     9  
1  4 18
  1  0  1  41372  17984 327164 2114008    0    1    40  5950 1114  2211  
1 12 87
  2  0  2  41404  18092 328028 2113008    0    4     7  7614 1316  2906  
3 25 73
  0  1  1  41440  17992 327164 2113932    0    7    10 12749 1302  3154  
3 21 76
  0  1  1  41512  18056 326992 2113972    0    9    12 10131 1510  3729  
3 20 77
  0  1  2  41580  18044 326760 2114232    0    7     6  8163 1275  3128  
2 24 73
  3  0  1  41604  17900 327852 2113244    0    4     8  8453 1324  3079  
2 15 83

Also, rsync again was the program using the largest amount of RAM (RSS, 
VSZ).

[2087] # ps uax --sort=-vsz | head -5
USER       PID %CPU %MEM   VSZ  RSS TTY      STAT START   TIME COMMAND
root     20562  2.6 15.1 585000 550936 pts/1 S    07:09   4:39 rsync 
-av ...
root     20686 12.0 15.6 585000 570284 pts/1 D    08:08  14:04 rsync 
-av ...
root       601  0.0  0.0 20884  592 ?        S    Aug31   0:04 ypbind
root       713  1.0  0.0  7276  340 ?        S    Aug31 147:43 3dmd



Regards,
- Robert
http://www.cwelug.org