Mr Roooster <mrroos...@gmail.com> writes: > I'm not sure they did a lot more than expose the ARC limit as a sysctl.
I'm not either, but if there is a precise description/code of what they did, that lowers the barrier to us stealing* it. (* There is of course a long tradition of improvements from various *BSD being applied to others.) > I moved to FreeBSD from Net a few years ago (mainly to get ZFS), and > have had similar issues under heavy load with a large ARC. It wouldn't > crash or hang, but it would always favour killing something over > flushing the ARC under pressure. I did a little bit of digging and got > the impression this was the way it was intended to work. (Although > reading this thread it may be a little more complex than that. :) ) Somebody may intend that, but it seems obviously buggy to kill processes than to drop data from a cache. > Once I limited my ARC my problems went away. I limited mine to 16 gig > on a 96 gig system, but I was running some processes with high memory > usage. I've not had cause to increase it though, and the system runs > reliably. It has a few zpools, and I'm running a VM of an iSCSI > exposed ZVOL, so it get a decent amount of use. Did I hear that right -- you had problems on a 96 GB system with the default settings? What was the default limit? Did you -- or could you -- characterize the performance impact on ZFS of having ARC limited to say 8/16/24G? And is this with spinning disks or SSD, with or without L2ARC? > (This is my home system, not a production system, however it does have > something like 10 HDDs in, so is often quite I/O loaded). Wow, that's a lot of disks!