On Mon, Mar 16, 2026 at 4:16 PM Garrett Wollman <[email protected]> wrote: > > <<On Mon, 16 Mar 2026 15:55:59 -0600, Alan Somers <[email protected]> said: > > > On Mon, Mar 16, 2026 at 3:39 PM Garrett Wollman <[email protected]> > > wrote: > > >> None of our systems are set up for that. They all have huge memory > >> and pretty tiny swap partitions, and in any case, they don't panic, > >> they just deadlock. Or the OOM killer just shoots all user processes; > >> these are nearly indistinguishable from a service provider's > >> perspective. > > > Pretty tiny swap partitions? > > Tiny compared to RAM, typically 16 or 32 GiB. After all, these are > NFS servers, they shouldn't have more than a few dozen MiB of > swappable anonymous memory.(*) We're not going to put a 2T SSD as a > hopefully-never-to-be-used swap drive in a file server.
You won't need a 2 TB SSD. By default, FreeBSD will make a mini dump, which excludes most of ARC and most memory used by userspace programs. For example, a recent core dump of mine takes 40 GB on a system with 1 TB of RAM. Note that I'm setting dumpon_flags="-Z" to enable core dump compression. That makes the dump go faster, as well as use less space. See dumpon(8) for more information about full vs mini core dumps. > > I configured a dump device on the server that crashed today, if it > crashes again when I'm at a keyboard I'll see if I can get to write a > dump in the 32 GiB of swap that it has configured. > > -GAWollman > > (*) If the kernel erroneously thinks it's out of free memory and > swapping stuff out only opens up a few MiB, that would certainly > explain why it goes on to ARC eviction and eventual OOM. On this > server, after two hours of uptime, I see: > > Device 1K-blocks Used Avail Capacity > /dev/gpt/swap0 33554432 32132 33522300 0% >
