is TMPFS still highly experimental?

[Ivan Voras]

On 02/10/2011 07:27, Xin LI wrote:

> The problem Ivan have asserted was not confirmed by anyone who have
> swap configured properly.  Gleb have pointed out that it might be
> related to a series of integer overflow by the way (he have also fixed
> a lot of tmpfs issues by the way).

Well, instead of guessing I can point you to the way I got the original
situation - you said you have ZFS configured so it would be easy for you
to check.

You should to something like this:

	- configure your system to the best of your abilities (but post what
you did different from the defaults)
	- install postgresql (8.4+, but I don't think the version is
important), configure it so it gets half the system memory or 2/3 the
system memory for its shared_buffers.
	- install pgbench
	- initialize pgbench so that the database definitely is larger than the
entire memory you got (NOTE: THIS IS NOT A CONTRIVED TEST - lots of
databases in practice are larger than the RAM in the server).
	- run pgbench & observe the results.

This should create really bad contention problem for memory between
postgresql and ZFS, which should manifest itself in tmpfs shrinking to 0
bytes free.

If you don't get this problem then great, it might be solved!


(for more info on pgbench, see this:
http://www.westnet.com/~gsmith/content/postgresql/pgbench-scaling.htm).