Date: Thu, 22 Mar 2012 15:00:35 +0000 From: Traiano Welcome <Traiano.Welcome@mtnbusiness.co.za> To: John Baldwin <jhb@freebsd.org>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: FreeBSD: syslog-ng: I/O error occurred while writing; fd='xx', error='No buffer space available (yy)' Message-ID: <CB910A60.DEED%traiano.welcome@mtnbusiness.co.za> In-Reply-To: <201203220816.58217.jhb@freebsd.org>
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Hi John On 22/03/2012 14:16, "John Baldwin" <jhb@freebsd.org> wrote: >On Thursday, March 22, 2012 6:03:21 am Traiano Welcome wrote: >> Hi List >>=20 >> I've been seeing the following in the messages log of my freebsd syslog >> server for quite some time now: >>=20 >> --- >> Mar 20 12:19:12 syslog2 syslog-ng[35313]: I/O error occurred while >> writing; fd=3D'12', error=3D'No buffer space available (55)' >> Mar 20 12:19:12 syslog2 syslog-ng[35313]: Connection broken; >> time_reopen=3D'60' >> Mar 20 12:19:12 syslog2 syslog-ng[35313]: I/O error occurred while >> writing; fd=3D'13', error=3D'No buffer space available (55)' >> Mar 20 12:19:12 syslog2 syslog-ng[35313]: Connection broken; >> time_reopen=3D'60' >> --- >>=20 >> These happen at a frequency of about 7 per minute on average. See >>attached >> trend graphs for an idea of the volume of traffic we're doing, as well >>as >> the memory and cpu utilisation trends on this server during this period. >> As can be seen from the graphs, load does not seem to be the issue. >> Occasionally during the week, the system freezes and requires a reboot, >>I >> think it's related to the above message, though I'm not sure. >>=20 >> My question is: What does this error mean, and how can I resolve it? >>=20 >> I have tried to frame this as an operating system kernel resource issue, >> and experimented with increasing the freebsd kernel sysctls for UDP >> performance: > >It means that the network driver has "filled" up with packets. Are you >using=20 >igb(4)? We have to crank the number of descriptors assigned to igb to >the max=20 >to workaround this at work (we get DNS timeouts during a simple boot >otherwise). hw.igb.maxtxd is the tunable you would set. The max value >you=20 >can set it to is 4096. Thanks for the clue. It seems igb is indeed being used. However, I not that when I try to list this tunable, I don't get anything: --- [root@syslog2]# sysctl -a | grep igb [root@syslog2]# --- --- [root@syslog2 /boot]# sysctl hw.igb.maxtxd=3D4000 sysctl: unknown oid 'hw.igb.maxtxd' --- Is this due to the way igb is compiled into the kernel, or am I tuning in the wrong place :-) > >--=20 >John Baldwin
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