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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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