Re: Chasing OOM Issues - good sysctl metrics to use?
Date: Sun, 24 Apr 2022 02:20:24 UTC
On 4/23/22 12:31, Mark Millard wrote: > I think you may have taken my suggestion backwards . . . > > Unfortunately, vnode (file) based swap space should be *avoided* > and partitions are what should be used in order to avoid deadlocks: > > On 2017-Feb-13, at 7:20 PM, Konstantin Belousov <kostikbel at gmail.com> wrote > on the freebsd-arm list: > > QUOTE > swapfile write requires the write request to come through the filesystem > write path, which might require the filesystem to allocate more memory > and read some data. E.g. it is known that any ZFS write request > allocates memory, and that write request on large UFS file might require > allocating and reading an indirect block buffer to find the block number > of the written block, if the indirect block was not yet read. > > As result, swapfile swapping is more prone to the trivial and unavoidable > deadlocks where the pagedaemon thread, which produces free memory, needs > more free memory to make a progress. Swap write on the raw partition over > simple partitioning scheme directly over HBA are usually safe, while e.g. > zfs over geli over umass is the worst construction. > END QUOTE > > The developers handbook has a section debugging deadlocks that he > referenced in a response to another report (on freebsd-hackers). > > https://docs.freebsd.org/en/books/developers-handbook/kerneldebug/#kerneldebug-deadlocks d'oh - thanks for the correction! -pete -- Pete Wright pete@nomadlogic.org @nomadlogicLA