kernel: negative sbsize for uid = 0

Doug Barton dougb at FreeBSD.org
Tue Dec 13 21:52:35 UTC 2011


I'm running 8.2-RELEASE-p4 i386 on some web servers that are generally
lightly-moderately loaded, but occasionally see some heavy spikes where
load average goes way up. When that is happening, but sometimes even
when it's not, I get hundreds of this message spewing into the logs:

kernel: negative sbsize for uid = 0

I haven't found anything particularly useful by searching for that
message, the one reference was to mbufs, but that seems not to be the
problem. Here is the output of 'netstat -m' during one of the load spikes:

598/1712/2310 mbufs in use (current/cache/total)
559/1533/2092/32768 mbuf clusters in use (current/cache/total/max)
559/1105 mbuf+clusters out of packet secondary zone in use (current/cache)
0/528/528/16384 4k (page size) jumbo clusters in use
(current/cache/total/max)
0/0/0/8192 9k jumbo clusters in use (current/cache/total/max)
0/0/0/4096 16k jumbo clusters in use (current/cache/total/max)
1267K/5606K/6873K bytes allocated to network (current/cache/total)
0/0/0 requests for mbufs denied (mbufs/clusters/mbuf+clusters)
0/0/0 requests for jumbo clusters denied (4k/9k/16k)
0/2239/6656 sfbufs in use (current/peak/max)
0 requests for sfbufs denied
0 requests for sfbufs delayed
809790 requests for I/O initiated by sendfile
0 calls to protocol drain routines

So is this message something to worry about? If so, how can I diagnose
what's happening, and how do I fix it?


Doug


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