Date: Wed, 5 Mar 2003 20:59:14 -0500 From: taxman <taxman@acd.net> To: Kirk Strauser <kirk@strauser.com>, freebsd-questions@freebsd.org Subject: Re: How many mbufs do I need? Message-ID: <200303052059.14368.taxman@acd.net> In-Reply-To: <87bs0ppk4d.fsf@strauser.com> References: <87bs0ppk4d.fsf@strauser.com>
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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? To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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