imapd Kernel-mode CPU Usage is Much Higher Than User-Mode (Doc ID 1289994.1)

Last updated on SEPTEMBER 14, 2016

Applies to:

Oracle Communications Messaging Server - Version 6.0.0 and later
Information in this document applies to any platform.
***Checked for relevance on 17-Feb-2014***

Symptoms

Kernel/system mode CPU is much higher than user mode and seems to be associated with imapd processes.  For example, prstat output like:

   PID USERNAME SIZE  RSS  STATE PRI NICE      TIME  CPU PROCESS/NLWP
  6076   nsmail  18G 2460M cpu29  50    0 1099:19:4  24% imapd/254
  6074   nsmail  17G 2367M cpu38   0    0 1094:39:3  18% imapd/254
  6075   nsmail  18G 2375M cpu36   0    0 1091:39:0  18% imapd/254
  6073   nsmail  17G 2333M cpu37   0    0 1098:16:3  16% imapd/254
 27462   nsmail  92M   64M cpu12  20    0   0:00:15 0.7% imdbverify/1
 24134   nsmail 135M  119M cpu36  32    0   0:05:43 0.3% tcp_smtp_server/8
  6070   nsmail  43M   28M sleep  59    0  16:15:33 0.1% enpd/14
 27542   nsmail  38M   22M sleep  55    0   0:00:00 0.0% reprocess/1
 27578   nsmail  39M   23M sleep  50    0   0:00:00 0.0% smtp_client/2
 27584   nsmail  39M   22M sleep  21    0   0:00:00 0.0% smtp_client/1


and vmstat output like:

 kthr        memory            page                   disk             faults       cpu
 r b w    swap    free    re   mf   pi   po   fr de sr s0 s1 s2 sd   in  sy     cs  us sy id
 0 1 0 48550672 53752152 1195  792 1821 3366 3366 0  0  2  2 -0 -0  8050 15988 8468  3  8 89
34 2 0 44878664 48449128 2972 2393 2650 3610 3609 0  0  2  2  0  0 11572 28164 9746  7 80 14
26 3 0 44863880 48546920 2470 1538 2540 4157 4157 0  0  3  3  0  0 10756 24328 9524  5 66 29
19 3 0 44873800 48549704 1990 1601 2560 1786 1785 0  0  3  3  0  0 10216 23219 9512  5 58 37
28 4 0 44879424 48551616 1550  908 1556 2590 2590 0  0  3  3  0  0  9049 18195 7910  4 47 49


The number of kernel threads ready to run but there is no CPU available (the 'r' column in the vmstat output) and the number threads in the imapd processes (the 'NLWP' column in the prstat output) and the amount of system mode CPU as compared to user mode indicate a problem.

Cause

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