MailScanner slow and not taking all resources available

[Ugo Bellavance]

Hi,

This is MailScanner version 4.54.6

It sometimes happen on some servers (not always the same) that suddenly, 
the INQ grows very fast.  When I look at the server, CPU is used only 
at ~ 50% or less and MailScanner is not using the CPU that much.

- The networks seems to be ok (I can easily download a file at 1 MB/s 
(10mbps link).
- DNS resolution seems to be quick
- SA doesn't time out
- System doesn't swap
- disk i/o doesn't look saturated

Here is an excerpt of dstat output:
----total-cpu-usage---- -dsk/total- -net/total- ---paging-- ---system--
usr sys idl wai hiq siq|_read _writ|_recv _send|__in_ _out_|_int_ _csw_
  51   9  30   9   1   1|   0  1032k|  41k  246k|   0     0 | 998   857
  64   6  29   0   1   1|   0   136k|  32k  286k|   0     0 | 808   550
  53   8  39   0   0   1|   0     0 |  61k  625k|   0     0 |1179   530
  80  13   8   0   0   1|   0     0 |  30k  319k|   0     0 | 846  1350
  80   9  10   0   1   1|   0     0 |  41k  311k|   0     0 | 824   485
  84   6  10   0   0   1|   0  1264k|  29k  281k|   0     0 | 913   510
  54  13  32   0   1   1|   0     0 |  45k  327k|   0     0 | 950   579
  74  10  16   0   0   2|   0     0 |  52k  317k|   0     0 | 953   984
  54  16  30   0   0   1|   0     0 |  64k  323k|   0     0 | 995   676
  18   6  76   0   0   1|   0     0 | 122k  292k|   0     0 |1152  1053
  62  13  16   9   1   0|   0    19M|  74k  255k|   0     0 |1356  1154
  64  13  22   0   1   1|   0     0 |  45k  317k|   0     0 | 917   937
  68   8  25   0   0   0|   0     0 |  51k  325k|   0     0 | 923   558
  44  21  34   0   1   2|   0   184k|  47k  299k|   0     0 | 969   647
  47  20  20  13   0   2|   0    19M|  44k   96k|   0     0 |1002   634

top:

  10:07:18  up 40 days,  1:22,  2 users,  load average: 1.62, 1.20, 1.07
95 processes: 94 sleeping, 1 running, 0 zombie, 0 stopped
CPU states:  cpu    user    nice  system    irq  softirq  iowait    idle
            total   12.0%    0.0%    6.2%   0.0%     0.4%    0.3%   80.6%
            cpu00   14.2%    0.0%    5.0%   0.2%     0.6%    0.4%   79.6%
            cpu01    9.9%    0.0%    7.5%   0.0%     0.3%    0.3%   81.6%
Mem:  3074084k av, 2809584k used,  264500k free,       0k shrd,  134216k 
buff
                    2141452k actv,  470156k in_d,   25672k in_c
Swap: 2008104k av,    7580k used, 2000524k free                 1809200k 
cached

   PID USER     PRI  NI  SIZE  RSS SHARE STAT %CPU %MEM   TIME CPU COMMAND
18116 root      18   0 78476  76M  3264 S     3.6  2.5   0:00   1 
MailScanner
15502 root      15   0  390M 390M   784 S     3.3 13.0   1:20   1 
milter-greylist
15970 root      25   0 13104  12M  3400 S     2.6  0.4   0:10   1 php
  7807 root      15   0  390M 390M   784 S     1.0 13.0   0:21   1 
milter-greylist
  7843 root      16   0  390M 390M   784 S     0.9 13.0   0:28   1 
milter-greylist
17886 root      15   0 78240  76M  3264 S     0.5  2.5   0:00   1 
MailScanner
22380 root      15   0 76008  74M  3248 S     0.1  2.4   0:25   1 
MailScanner
17840 root      15   0  1056 1056   812 R     0.1  0.0   0:00   0 top


Anyone seeing this as well?