Using TMPFS for /tmp and /var/run?
David Wolfskill
david at catwhisker.org
Mon Apr 2 10:59:34 UTC 2012
On Mon, Apr 02, 2012 at 01:31:19PM +0300, Gleb Kurtsou wrote:
> ...
> > > In any case, effective maximum usable size for tmpfs involves SIZE_MAX
> > > (~4G) & PAGE_SIZE (4K, in my case).
>
> size_t is 64-bit on 64-bit archs.
OK. Still, the requirement that the "size" specification be in "bytes"
is awkward (in my experience) -- and I was using i386.
> > > * Even when I went ahead and created a tmpfs for /tmp, I'd get ENOSPC
> > > whenever I tried to allocate anything on it -- until I dropped the
> > > size specification to <2G (2**32). Well, 2GB for /tmp just wasn't at
> > > all likely to be useful for my purposes in this case.
>
> Are you using ZFS alongside tmpfs? It should be fixed in 9-STABLE.
I have not tried ZFS yet. I don't expect to do so unless I switch to
amd64.
> ...
> > It seems there is only one switch which determines the size of the tmpfs
> > in question (size) and there is no convenient way to say what amount of
> > RAM is being used before using the swap space. I'd like to have at least
> > a knob determining the limit of RAM being used.
>
> There is no way to force tmpfs to use given amount of RAM only. It's VM
> subsystem that decides what pages to swap. Although some tweaking for VM
> to prefer swapping tmpfs pages prior to process pages would be nice.
>
> You could try the patch attached. It adds support for size option suffixes
> (like 1g) and introduces swap limit (part of the older patch, not sure
> if it's any use).
>
> Patch is against 10-CURRENT.
> Older version: https://github.com/glk/freebsd-head/commit/3bd8f7d
> ...
I'll plan to try this on a currrently-underutilized slice on my laptop,
then -- thanks! :-)
Peace,
david
--
David H. Wolfskill david at catwhisker.org
Depriving a girl or boy of an opportunity for education is evil.
See http://www.catwhisker.org/~david/publickey.gpg for my public key.
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