[Snort-users] Performance monitoring issues

Lee Saunders lee.saunders at ...16528...
Fri Sep 6 06:45:14 EDT 2013


I've been starting performance monitoring on my setup, as there is 
unexpected drops appearing at one single installation (virtualized 
configuration so traffic profile pretty similar to other installation).

The bandwidth is pre-filtered so is relatively small, certainly small 
enough to that drops are not currently expected. The first perculiarity 
is looking at perfmon I see patmatch-percent numbers in the range 70 - 
300%, very high and not what I'd expect.

Looking then at profile monitoring, I can't find much on how to read and 
act on the values. I'm currently running a test for the rules profiling, 
but a preprocessor profile based on total ticks sorting has raised a 
couple of queries. The output of a short run is repeated below. However, 
the rtn eval value, when looked at against other outputs on the web 
looks very high, at 622810 ms, but not clear this represents or how to 
improve it. There is also the implication from the output that this and 
rule tree eval are siblings of rule eval, but the % of parent then does 
not add up, with a value of around 170% - is there a known problem with 
how these are reported and a red herring?

I'm at the outset of the tuning exercise, but its proving difficult to 
find resources which outline how to interpret these values and how to 
mitigate them. I'm assuming the top offending detect is influenced 
primarily by the rule definitions hence the rules profiling I'm 
currently doing, but some insight into minimizing the subtasks would be 
useful, and if any of the other preprocessors can influence.

timestamp: 1378398556
Preprocessor Profile Statistics (all)
==========================================================
  Num            Preprocessor Layer     Checks      Exits Microsecs  
Avg/Check Pct of Caller Pct of Total
  ===            ============ =====     ======      ===== =========  
========= ============= ============
   1                   detect     0      10553 10553              
873142      82.74         83.64        83.64
    1               rule eval     1      10427 10427              
752623      72.18         86.20        72.09
     1         rule tree eval     2      21935 21935              
750099      34.20         99.66        71.85
      1               content     3       4836 4836                
1449       0.30          0.19         0.14
      2                  pcre     3         19 19                
1438      75.71          0.19         0.14
      3                 flags     3       8970 8970                 
656       0.07          0.09         0.06
      4             byte_test     3       2929 2929                 
517       0.18          0.07         0.05
      5              dsize_eq     3       3987 3987                 
402       0.10          0.05         0.04
      6                  flow     3       2021 2021                 
172       0.09          0.02         0.02
      7  preproc_rule_options     3       1256 1256                  
88       0.07          0.01         0.01
      8            uricontent     3        168 168                  
64       0.38          0.01         0.01
      9                 itype     3        318 318                  
40       0.13          0.01         0.00
     10              flowbits     3        212 212                  
32       0.15          0.00         0.00
     11                 icode     3        285 285                  
14       0.05          0.00         0.00
     12             file_data     3        123 123                   
5       0.04          0.00         0.00
     13          byte_extract     3          6 6                   
3       0.52          0.00         0.00
     14              isdataat     3          8 8                   
1       0.20          0.00         0.00
     15                window     3          4 4                   
0       0.15          0.00         0.00
     2               rtn eval     2    1039167 1039167              
622810       0.60         82.75        59.66
    2                    mpse     1      10212 10212               
87608       8.58         10.03         8.39
   2                       s5     0       9321 9321               
86594       9.29          8.29         8.29
    1                   s5tcp     1       8062 6651               
64012       7.94         73.92         6.1310
     1             s5TcpState     2       6651 6651               
46814       7.04         73.13         4.48
      1             s5TcpData     3       1606 1606                
5624       3.50         12.01         0.54
       1       s5TcpPktInsert     4       1406 1406                
4829       3.43         85.86         0.46
      2            s5TcpFlush     3       1037 1037                
2863       2.76          6.12         0.27
       1  s5TcpProcessRebuilt     4        892 892               
50297      56.39       1756.44         4.82
       2     s5TcpBuildPacket     4        892 892                 
665       0.75         23.25         0.06
     2           s5TcpNewSess     2        197 197                
1075       5.46          1.68         0.10
   3                      ssl     0       2090 2090               
20935      10.02          2.01         2.01
   4                   decode     0       9853 9853               
20088       2.04          1.92         1.92
   5           sensitive_data     0        162 162               
14964      92.37          1.43         1.43
   6                   eventq     0      20562 20562                
6610       0.32          0.63         0.63
   7                     smtp     0       3748 3748                
5387       1.44          0.52         0.52
   8              httpinspect     0       3782 3782                
5162       1.36          0.49         0.49
   9               DceRpcMain     0       2865 2865                
3518       1.23          0.34         0.34
    1           DceRpcSession     1       2865 2865                
2745       0.96         78.01         0.26
     1       DceRpcNewSession     2       2865 2865                
1584       0.55         57.72         0.15
  10                  perfmon     0      10721 10721                
3119       0.29          0.30         0.30
  11                      ssh     0       2433 2116                
1805       0.74          0.17         0.17
  12                      pop     0       3707 3707                
1434       0.39          0.14         0.14
  13                     imap     0       3707 3707                
1254       0.34          0.12         0.12
  14                      sip     0       3692 3692                 
842       0.23          0.08         0.08
  15                   modbus     0       3707 3707                 
692       0.19          0.07         0.07
  16                     dnp3     0       1259 1259                 
572       0.46          0.05         0.05
  17              backorifice     0       1259 1259                 
437       0.35          0.04         0.04
  18                      dns     0        820 820                 
164       0.20          0.02         0.02
  total                 total     0       9835       9835 1043957     
106.15          0.00         0.00




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