Top not showing cpu usage even remotely accurately

[Tamouh H.]

> But since running 5.x (5.5-STABLE since 1st Aug) top can show 
> 0.0% idle but the cpu usages shown don't add up to much of a 
> fraction of 100%.
> 
> For a typical illustration: 'make index' has been running for 
> hours, and here's a shot of 'nice top', o)rdered by cpu, 
> showing S)ystem procs: 
> 
> last pid: 62397;  load averages:  2.06,  2.09,  2.13      up 
> 3+03:57:39 13:11:27
> 154 processes: 6 running, 125 sleeping, 23 waiting CPU 
> states: 77.3% user,  0.0% nice, 22.7% system,  0.0% 
> interrupt,  0.0% idle
> Mem: 79M Active, 24M Inact, 37M Wired, 5640K Cache, 25M Buf, 
> 3388K Free
> Swap: 384M Total, 133M Used, 251M Free, 34% Inuse
> 
>   PID USERNAME PRI NICE   SIZE    RES STATE    TIME   WCPU    
> CPU COMMAND
> 62380 root     122    0   788K   648K RUN      0:01 19.48%  1.86% make
>   736 smithi    97    0 27000K  3184K select  89:56  1.07%  
> 1.07% kdeinit
>   762 smithi    96    0 29708K  7428K select  14:01  0.93%  
> 0.93% kdeinit
>   699 smithi    96    0 52320K 10288K select 105:02  0.88%  0.88% Xorg
> 62394 root     125    0   580K   440K RUN      0:00  7.00%  0.34% make
>   754 smithi    96    0 30972K  6308K select  57:22  0.15%  
> 0.15% kdeinit
>   770 smithi     8    0  2524K   660K nanslp  20:51  0.05%  
> 0.05% ascpu

> 'ps auxww' cpu percentages reveal little more, except that 
> make index is running 'make -j2 ..' hence the ~2.0 load average.
> 
> Ignore the high swap use; most of it is numerous quiescent 
> kwrite, httpd and mozilla sessions pushed out to swap on this 
> lil' 160MB laptop; 'systat -vm' shows it's not actually doing 
> any paging during this time.
> 
> Any ideas why top hasn't much of a clue about what's consuming cpu? 
> 
> Cheers, Ian

I've the same issue with FBSD 5.4 and TOP. In fact, the load averages are so irrelevant now that I barely pay attention to them. The server goes to 4 or 6 load averages without slowing down, and other times the load average would be 0.8 and the server is running slow.

An example of unmatching TOP:

last pid: 17889;  load averages:  0.60,  0.52,  0.50                                                  up 3+17:22:33  00:41:45
186 processes: 2 running, 183 sleeping, 1 lock
CPU states: 30.0% user,  0.0% nice,  1.7% system,  0.1% interrupt, 68.3% idle
Mem: 1678M Active, 1110M Inact, 287M Wired, 87M Cache, 112M Buf, 103M Free
Swap: 8762M Total, 1584K Used, 8760M Free

  PID USERNAME PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU COMMAND
 5071 nobody   101    0 43124K 35180K CPU2   2   0:07 14.89% 14.89% httpd
14409 nobody     4    0 43940K 36076K sbwait 0   0:01  1.22%  1.22% httpd
95515 nobody     4    0 39892K 32188K sbwait 1   0:08  0.29%  0.29% httpd
17656 prpcon     4    0  9916K  5680K sbwait 1   0:01  0.26%  0.24% cppop
18006 root       8    0  3032K  2324K nanslp 0  25:35  0.05%  0.05% perl
  783 root      96    0  9704K  4572K select 3  17:39  0.05%  0.05% cppop
 3820 mysql     20    0   339M   251M kserel 3  43:34  0.00%  0.00% mysqld
  744 root       8   20 16776K 15120K nanslp 0  40:53  0.00%  0.00% perl
72899 root      20    0 21704K 20128K kserel 3  30:25  0.00%  0.00% clamd
  913 root      97    0 11616K  4864K select 3   5:27  0.00%  0.00% cpsrvd
 1065 mailnull  96    0  5880K  2828K select 0   3:22  0.00%  0.00% exim-4.62-0