MailScanner running very slow

[Nasser Al-Zawawi]

Hi,
I have a Dell PowerEdge server 2950 with 2 Dual Core Xeon processors
3.0GHz with 2GB RAM running RedHat ES 4.  The MTA is sendmail and I am
using the latest MailScanner version (4.70.7-1).  The system processes
about 2,000 emails per day and about half of it are spam.  See the
following:
#---------------
MailScanner Status:
      1920 messages Scanned by MailScanner
      73657132 Total Bytes
      1122 Spam messages detected by MailScanner
      6 Viruses found by MailScanner
      935 Messages delivered by MailScanner
#---------------
 
The mail delivery is very slow.  Some time it takes 2 hrs before it gets
delivered.  I tried the tips under
http://wiki.mailscanner.info/doku.php?id=documentation:tweaking:some_thi
ngs_to_try_if_your_incoming_queue_is_running_slow but they did not help.
The mail keeps accumulating under /var/spool/mqueue.in while all the
MailScanner processors are running at 100% CPU.  Then all the sudden
(after 1-2 hours) it starts delivering the emails and the
/var/spool/mqueue.in files go down to 0.
I monitored the system today; the system stopped delivering emails
between 9:12AM till 11:35AM.  During that time, top showed something
like this:
#----------------
top - 10:46:26 up 3 days,  7:42,  1 user,  load average: 5.81, 6.09,
5.48
Tasks: 233 total,   5 running, 226 sleeping,   0 stopped,   2 zombie
Cpu(s): 59.0% us,  1.2% sy,  0.0% ni, 39.5% id,  0.2% wa,  0.0% hi,
0.0% si
Mem:   2074600k total,  1735692k used,   338908k free,    22524k buffers
Swap:  2097144k total,   356516k used,  1740628k free,   532576k cached
 
  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 2752 root      25   0 85572  75m 2964 R  100  3.7  35:54.85 MailScanner
 2880 root      25   0 85572  75m 2956 R  100  3.7  35:50.35 MailScanner
 3024 root      25   0 85572  75m 2956 R  100  3.7  35:41.62 MailScanner
 2949 root      25   0 85572  75m 2956 R  100  3.7  35:47.07 MailScanner
11393 apache    15   0 26360 9736 3648 S    5  0.5   0:57.14 httpd
11394 apache    15   0 26576 9936 3616 S    5  0.5   0:58.83 httpd
26598 root      16   0  4760 2568 1648 S    1  0.1   0:00.20 ssh
#----------------
 
and the /var/spool/mqueue.in continued to accumulate files till it
reached 489 messages, then within 5 minutes it delivered all the
messages!
 
This cycles continues all day long, where the emails are withheld for 1
to 2 hours and then the get delivered in one big burst.
 
Here are snippets of the log for that period with "Log Speed = yes":
 
grep ": Batch" /var/log/maillog
#-----------
Aug 13 09:12:16 samba MailScanner[5852]: Batch completed at 1844 bytes
per second (39583 / 21)
Aug 13 09:12:16 samba MailScanner[5852]: Batch (2 messages) processed in
21.46 seconds
Aug 13 09:12:42 samba MailScanner[6013]: Batch completed at 3752 bytes
per second (9167 / 2)
.
Aug 13 11:28:55 samba MailScanner[2949]: Batch (10 messages) processed
in 24.54 seconds
Aug 13 11:28:55 samba MailScanner[3024]: Batch completed at 657 bytes
per second (3825 / 5)
Aug 13 11:28:55 samba MailScanner[3024]: Batch (1 message) processed in
5.82 seconds
#-----------
I would appreciate any clues on resolving this issue.
 
Best regards,

Nasser
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