Help:: Listen queue overflow killing servers

[James B. Byrne]

>>>>> On 7/26/19 4:58 AM, Paul Macdonald via freebsd-questions wrote:
>>>>>> Over the past few months i've seen several boxes (4 or 5) become
>>>>>> unresponsive as a result of a Listen queue overflow state.

Since upgrading our hosts to 12.0 we have experienced many 'lockouts'
of both bhyve vm guests and jails, all running on zfs.  There are
known issues with Bhyve guests getting into a deadlock state waiting
on zio or encountering memory exhaustion in releases after
FreeBSD-11.1. This has multiple causes:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=231117
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=187594

We have worked around this by restricting max ARC to the net of system
memory minus all vm allocations minus 4GB.  We also noted that as the
capacity of zfs pools approached 80% the deadlock is encountered more
frequently.

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James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
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