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Re: Summary: Moving /tmp to tmpfs makes it useless

On Sun, Jun 10, 2012 at 06:13:24PM +0300, Serge wrote:
> 2012/6/10 Wouter Verhelst wrote:
> > Sorry, but this is a biased summary, and therefore useless for what it
> > intends to be.
> Yes, I know. It's biased toward the /tmp and real-world applications.
> >> "/tmp on tmpfs is good" quotes
> >> No real quotes here. Most of this and other threads were about why
> >> /tmp on tmpfs is not that bad. But there're no real quotes explaining
> >> why it's good.
> >
> > This is wrong. There were several (including by me). You dismissed them,
> > not considering them valid, but that doesn't mean they are.
> I dismissed everything that was not related to /tmp or some popular apps.
> A lot of people (including you) said that tmpfs makes things faster. But
> there were no examples of popular use-cases becoming faster because
> of /tmp on tmpfs, so I had nothing to quote.

You're not even trying.

if tmpfs is faster than (say) ext4, then anything which uses /tmp will
obviously speed up.

Can I provide a use case where this will matter? Not necessarily. But
then, can you provide a use case where this will *not* matter? Really?

> Nobody could provide examples or numbers of how much /tmp on tmpfs reduces
> amount of writes, and tests showed that tmpfs+swap may even increase amount
> of writes (hence not always good for SSD),

True, but then swapping to an SSD is the "best" idea since "640kB is
enough for everyone" :-)

> tmpfs does not have 5% overflow safety,

Because it doesn't need it.

The 5% overflow safety exists for two reasons:
- to avoid excessive fragmentation (which is not relevant for tmpfs)
- to allow you to clean up when the filesystem does fill up. For tmpfs,
  you do that with:
  mount -o remount,size=foo /tmp
  where 'foo' is some size or percentage that's larger than what the
  tmpfs is currently mounted with. Now you clean up, and you reset to
  what it was before.

> > If you're going to post a thread summary, please do not filter out
> > information you don't agree with. Otherwise you're not posting a thread
> > summary, you're posting a 'my side of the fence' summary.
> I had to filter it.

Yes, but if you want to have any remote resemblance of objectivity, then
what you do not do is filter out everything you don't agree with.

The volume of a pizza of thickness a and radius z can be described by
the following formula:

pi zz a

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