On Wednesday 05 March 2003 04:40 pm, Kirk Strauser wrote:
I killed my FreeBSD 4.8-PRE (2003-02-18) server today by exhausting the
available mbufs. I'd seen warnings like All mbuf clusters exhausted,
please see tuning(7). in /var/log/messages, so I added
`kern.ipc.nmbclusters=16384' to /boot/loader.conf.local a while back.
This server has 768MB of memory, and I run at least two copies of
PostgreSQL (it has multiple jails) at any given time and use it to server
NFS to a couple of Linux clients. Today I wanted to test Bochs on one of
the Linux machines, ran the bochsconf program, watched it run createdisk
to make a 512MB disk image in my home directory, and saw the server panic
within a few seconds. When it came back up, I bumped nmbclusters to 32768,
rebooted, and tried createdisk it. This time I watched `netstat -m' as the
dreaded All mbuf clusters exhausted... message began to scroll up the
screen. This time, the server stayed alive, but it clearly maxed out all
available buffers. After createdisk was finished, the mbuf usage went back
to normal:
$ netstat -m
389/36736/131072 mbufs in use (current/peak/max):
389 mbufs allocated to data
388/32768/32768 mbuf clusters in use (current/peak/max)
74720 Kbytes allocated to network (33% of mb_map in use)
345 requests for memory denied
1 requests for memory delayed
0 calls to protocol drain routines
My questions are these:
1) Is there a guideline for how many nmbclusters to allocate? Short of
running out of physical memory, is there such a thing as too many?
2) I've already allocated 64MB to network buffering. This seems like a
huge amount to me. Is it?
3) Should running out of mbufs be expected to crash the server, or should I
try to reproduce it and file a PR?
Reproducible errors are the most helpful thing a developer can have to improve
FreeBSD's stability. So try to reproduce it, but make sure you're doing it
on the most recent -stable code, as your problem may already be fixed. If
you can update to -stable and still get that error then file a pr and ask on
the -stable mailing list as that is the appropriate place.
No idea on the rest, sorry,
Tim
4) What could createdisk have been doing to spike usage that heavily?
5) Could Linux's NFS client implementation have aggravated the situation?
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