is TMPFS still highly experimental?

[Xin LI]

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On 10/02/11 03:23, Olivier Smedts wrote:
> 2011/10/2 Xin LI <delphij at gmail.com>:
>> Hi,
>> 
>> On Sat, Oct 1, 2011 at 8:48 AM, Chris Rees <crees at freebsd.org>
>> wrote:
>>> I've also not heard of anyone using it with zfs successfully-
>>> it tends to shrink rapidly.
>> 
>> I'm quite surprised with this assertion.  I use tmpfs on my own
>> system and I never see such problem as long as one have
>> sufficient swap space.
> 
> The problem here is "sufficient swap space".
> 
> I've got 8G of RAM, and 2G of swap (just in case). When the ZFS
> ARC reaches 4G, there's no room for a single byte in tmpfs, even
> with 2G swap free and at least 2-3G RAM free. The swap size must be
> at least the RAM size if you plan on using ZFS and tmpfs. That's a
> problem for me because I'm short on disk space, and there's no
> point in having an enormous swap size (hey, minidumps !) when you
> already have lots of RAM, which is the case in most ZFS installs.

A possible workaround for this might be limiting ARC size?  I can't
think about any better idea at this point.

My personal experience is always have at least RAM sized swap because
the system may choose to write in-core data to swap which enables it
to discard these memory without expensive swapout in emergency cases.
 Depending on workload, this could give better responsiveness and
frankly I never consider having a few tens of GBs of swap as expensive
since large disks are not expensive nowadays...

Cheers,
- -- 
Xin LI <delphij at delphij.net>	https://www.delphij.net/
FreeBSD - The Power to Serve!		Live free or die
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