On 2017-Dec-06 10:01:02 +0000, Baptiste Daroussin <[email protected]> wrote: >Author: bapt >Date: Wed Dec 6 10:01:02 2017 >New Revision: 326619 >URL: https://svnweb.freebsd.org/changeset/base/326619 > >Log: > MFC r325851: > > remove the poor emulation of the IllumOS needfree global variable to prevent > the ARC reclaim thread running longer than needed. >
This change appears to break the backpressure mechanism that forces ARC to release wired memory. Running FreeBSD/amd64 r326743, I found that my system was thrashing badly with almost all memory (~31GB out of 32GB) wired (including 19GB ARC, 7GB VBox guests). Running a tool that just allocates and dirties a large amount of memory had no effect on the ARC size. Reverting this change only restores normal behaviour where ARC will shrink under pressure. My ZFS boot tunables are: vfs.zfs.arc_max="24G" vfs.zfs.arc_meta_limit="12G" -- Peter Jeremy
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