tmpfs out of space (ZFS related?)

Paul B Mahol onemda at
Sun Nov 21 23:29:12 UTC 2010

On Sun, Nov 21, 2010 at 10:42 PM, Ivan Voras <ivoras at> wrote:
> On 11/21/10 23:19, Eir Nym wrote:
>> On 22 November 2010 01:00, Eir Nym<eirnym at>  wrote:
>>> On 22 November 2010 00:47, Bruce Cran<bruce at>  wrote:
>>>> On Mon, 22 Nov 2010 00:43:03 +0300
>>>> Eir Nym<eirnym at>  wrote:
>>>>> Which type of MFS do you use? I think you shold use "swap-backed" for
>>>>> your /tmp, not "malloc-based". Last type is only for in-kernel file
>>>>> system.
>>>> It's tmpfs(5), not md(4).
>> I wonder if you can create FIFO and sockets with md(4). md(4) is
>> geometry, not filesystem.
> md is a GEOM class which presents several types of devices backed by virtual
> memory. You can create file systems on top of those and mount them.
> The downside is that each of those layers has its own copy of the original
> data (and them some).
> tmpfs OTOH is a "real" memory file system, without the need for a backing
> device, and it is more efficient with respect to data copies (not perfect -
> it still AFAIK has to maintain something like 2 copies).
AFAIK, if this was ever correct it is not any more.

Data copies can mean anything.

I use >1.5 GB file in tmpfs on 2GB RAM and 0B SWAP without problems.

>> tmpfs(5) doesn't support this file types as I can see in FreeBSD source
>> code.
> Maybe it is handled by default code, but they are supported. I have used
> tmpfs extensively for the last few years for mostly static servers (i.e.
> /tmp contains some sockets, a small number of short-lived temporary files,
> etc) - and it so far worked very well. This is actually the first time it
> failed me in some way.

It can be anything: overflow, race, memory corruption ...

Find way to reproduce it 100%.

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