[Dovecot] FreeBSD 6.1-RELEASE/kqueue high CPU load

[LI Xin]

Taras Savchuk wrote:
> LI Xin пишет:
>> Paul Lathrop wrote:
>>  
>>> Taras Savchuk wrote:
>>>    
>>>> Hi to ALL!
>>>>
>>>> I have dovecot-1.0r7 installed on FreeBSD 6.1, using kqueue and
>>>> Maildir (<20 mailboxes, < 0,5 Gb size). Periodically CPU load of imap
>>>> processes increasing up to 60-80%.
>>>> Is it normall behavior or not? May be somebody had such kind of
>>>> problems?
>>>>
>>>>       
>>> I have also experienced this behavior, which is quite bothersome because
>>> I sold my supervisor on Dovecot by talking about performance and low
>>> resource requirements...
>>>     
>>
>> What if you get some output from ktrace/kdump?  Additionally, try to
>> force the process to save a coredump and investigate its .core with gdb
>> would help tracking down the issue...
>>
>> Note that because when using kqueue the process should get a "kqread" if
>> it is waiting for kqueue event.  If the process is stuck in "RUN" state
>> then a coredump would be more helpful.
>>
>> Cheers,
>>   
> I cought imap while eating much CPU (~80%) and run ktrace -t + -p <bad
> process pid>.
> It's kdump -E output, many gettimeofday() calls, is it normal? :
> 
> mail2# kdump -E -f ktrace.out | less
> 26208 imap     0.000000 RET   kevent 0
> 26208 imap     0.000042 CALL  gettimeofday(0x80c2c60,0x80c2c68)
> 26208 imap     0.000046 RET   gettimeofday 0
> 26208 imap     0.000061 CALL  gettimeofday(0xbfbfe9a0,0)
> 26208 imap     0.000064 RET   gettimeofday 0
> 26208 imap     0.000078 CALL  kevent(0x4,0,0,0x80d1000,0x5,0xbfbfe998)
> 26208 imap     0.000082 RET   kevent 0
> 26208 imap     0.000100 CALL  gettimeofday(0x80c2c60,0x80c2c68)
> 26208 imap     0.000103 RET   gettimeofday 0
> 26208 imap     0.000116 CALL  gettimeofday(0xbfbfe9a0,0)
> 26208 imap     0.000119 RET   gettimeofday 0
> 26208 imap     0.000131 CALL  kevent(0x4,0,0,0x80d1000,0x5,0xbfbfe998)
> 26208 imap     0.474998 RET   kevent 0
[snip]

This looks quite normal...  I am not really sure about what is
happening.  Is the CPU consumed by in-kernel operation?  (systat -vm  or
top's output would be helpful)

Cheers,
-- 
Xin LI <delphij at delphij.net>	http://www.delphij.net/
FreeBSD - The Power to Serve!

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