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Date: Mon, 15 Jun 2009 23:12:50 -0400
From: Ben Kelly <ben@wanderview.com>
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To: Ivan Voras <ivoras@freebsd.org>
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Subject: Re: tmpfs experimental?
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Ivan Voras wrote:
> Hi,
> 
> Are there still known problems with tmpfs?
> 
> I've been using it for a while in 7-STABLE and 8-CURRENT without
> noticeable problems - not that there was ever serious load involved
> (normal /tmp activity). I've just tried it and it survived a couple of
> rounds of blogbench, even with virtual memory swapping.
> 
> In other words, is there still reason for the "highly experimental
> feature" warning?

I get some slightly unexpected behavior when mount <mountpoint> is run
multiple times:

  ianto# mount | grep ' /tmp'
  tmpfs on /tmp (tmpfs, local)
  ianto# mount /tmp
  ianto# mount | grep ' /tmp'
  tmpfs on /tmp (tmpfs, local)
  tmpfs on /tmp (tmpfs, local)
  ianto# umount /tmp
  ianto# mount | grep ' /tmp'
  tmpfs on /tmp (tmpfs, local)
  ianto#

It also occurred to me once that perhaps all tmpfs mounts should share
the same UMA zones instead of a new zone for each mount, but thats a
pretty minor issue:

  ianto# vmstat -z | grep TMPFS
  TMPFS dirent:    20,        0,        4,      165,      385,        0
  TMPFS node:      136,        0,        5,       53,      386,        0
  TMPFS dirent:    20,        0,        4,      165,     5541,        0
  TMPFS node:      136,        0,        5,       53,     5542,        0
  TMPFS dirent:    20,        0,        6,      163,    51031,        0
  TMPFS node:      136,        0,        7,       80,    46927,        0
  TMPFS dirent:    20,        0,        4,      165,     7542,        0
  TMPFS node:      136,        0,        5,       53,     7543,        0
  TMPFS dirent:    20,        0,        6,      163,    81644,        0
  TMPFS node:      136,        0,        8,       79,    77463,        0


Overall tmpfs has been very stable for me as a mimedefang spool directory.

Hope that helps.

- Ben