tmpfs out of space (ZFS related?)

[Daniel Braniss]

> On (21/11/2010 22:22), Ivan Voras wrote:
> > I got a curious error today while starting PostgreSQL, complaining about 
> > "out of space" errno while creating lock file on /tmp.
> > 
> > /tmp on this machine is mounted as tmpfs and indeed, here is the statistic:
> > 
> > biggie:/# df -i
> > Filesystem    1M-blocks  Used  Avail Capacity iused     ifree %iused 
> > Mounted on
> > /dev/mfid0s1a      9912  5193   3926    57%  306079   1012831   23%   /
> > devfs                 0     0      0   100%       0         0  100%   /dev
> > fdescfs               0     0      0   100%       4     11092    0% 
> > /dev/fd
> > tmpfs                 0     0      0   100%       9         0  100%   /tmp
> > tank             376044     0 376044     0%       4 770138347    0%   /tank
> > tank/ports       376658   614 376044     0%  145919 770138347    0% 
> > /usr/ports
> > tank/mysql       376073    29 376044     0%     102 770138347    0% 
> > /var/db/mysql
> > tank/pgdata90    400469 24425 376044     6%    1047 770138347    0% 
> > /tank/pgdata90
> > 
> > On the other hand, "top" reports this:
> > 
> > last pid: 79667;  load averages:  0.08,  0.68,  0.77    up 1+09:12:13 
> > 00:11:33
> > 44 processes:  1 running, 43 sleeping
> > CPU:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
> > Mem: 13M Active, 46M Inact, 15G Wired, 232K Cache, 1458M Buf, 8358M Free
> > Swap: 1024M Total, 1024M Free
> > 
> > Note the "8358M free" report.
> That's probably integer overflow, could you try specifying max
> size as mount option. There was a series of integer overflows in tmpfs.
> Used and available are 0 in df output. On my system I have:
> % df
> Filesystem         Size    Used   Avail Capacity  Mounted on
> tmpfs              4.3G    4.0K    4.3G     0%    /usr/obj/ports
> 
> Also note, that tmpfs does somewhat weired thing on constantly
> recalculating available space based on free memory/swap (not sure if
> specifying max size would fix it).
> 
> Did you try double copy elimination patch by kib@?
> http://lists.freebsd.org/pipermail/freebsd-fs/2010-June/008786.html
> 
> It doesn't apply cleanly to current any more, but fixing it shouldn't be
> hard. The patch wouldn't fix this particular issue but looks very
> promising.
> 
> Thanks,
> Gleb
> 
> > The server has ZFS and was doing IO intensive database work on it; the 8 
> > GB free memory comes from PostgreSQL being restarted and freeing the 
> > memory (but failing to start again...).
> > 
> > Starting PostgreSQL gets me this message:
> > Nov 22 00:18:24 biggie postgres[79696]: [1-1] FATAL:  could not write 
> > lock file "/tmp/.s.PGSQL.5432.lock": No space left on device
> > 
> > This is 8-STABLE amd64.
> > 
> > Running "touch /tmp/abc" works, and creates a file. Running "echo abc > 
> > /tmp/abc" doesn't return an error but *doesn't write anything to the 
> > file*, just creates a directory entry.
> > 
> > The status doesn't change over time, i.e. "df" on tmpfs always shows "0 
> > free".

out of space is sometimes caused by out of inodes.
what does df -i say?
you can increase the # of inodes, see man mdmfs

my .5
danny