[syslog-ng] dropped udp packets and help with config

[Gergely Nagy]

>>  We recently upgraded to Solaris 10 from Solaris 9 and I don't recall
>> us dropping that
>> many packets before. And we also upgraded from a very older Sylog-ng
>> version to 3.1.2.
>> I am basing the dropped packets on the udp stats, not syslog-ng stats.
>> Syslog-ng stats has NO dropped packets.
>
> In another thread someone was complaining similar issues on Solaris. It
> seems that the way syslog-ng writes log files (each line an individual
> write system call), seems to have an enormous overhead on Solaris, much
> more than on Linux.

Attached is a program that tries to measure the speed difference between
write() and writev(). It first writes N messages using write(), one by
one, then it writes the same N messages using writev(), IOV_MAX message
at a time.

On both Linux and Solaris (OpenIndiana, actually, but shouldn't be much
different on real Solaris), I get similar results: about 4 seconds for
the write()s to finish, and below 1 second for writev().

While the write()->writev() performance is noticable, the difference
between Solaris and Linux seems to be so very tiny, that it is pretty
much negligible.

(Unless, of course, I screwed up the test program, which is entirely
possible)

-- 
|8]

-------------- next part --------------
A non-text attachment was scrubbed...
Name: write-v-perftest.c
Type: text/x-csrc
Size: 2002 bytes
Desc: not available
Url : http://lists.balabit.hu/pipermail/syslog-ng/attachments/20110523/ff15f0e1/attachment.c