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Re: putting "/tmp" to memory help



On Tue, 25 Jan 2011 09:42:24 +0100
Jochen Schulz <ml@well-adjusted.de> wrote:

> Celejar:
> > 
> > I'm somewhat confused about this.  My system has 2GB of RAM, and I have:
> > 
> > $ uptime
> >  20:46:09 up 5 days,  5:30,  9 users,  load average: 0.06, 0.09, 0.25
> > 
> > $ free
> >              total       used       free     shared    buffers     cached
> > Mem:       2065172    1047312    1017860          0      66064     357512
> > -/+ buffers/cache:     623736    1441436
> > Swap:      1949688     102364    1847324
> 
> This shows that ~620MB are used for applications and data. About 400MB
> is used for buffers/cache (don't ask me what the difference is).
> 
> > $ df | grep tmp
> > tmpfs                  1032584        16   1032568   1% /lib/init/rw
> > tmpfs                  1032584         0   1032584   0% /dev/shm
> > none                   1032584      2440   1030144   1% /tmp
> > 
> > So my /tmp is using 1GB.
> 
> No. Your /tmp might grow up to 1GB, but it only occupies what's really
> necessary. This is the main difference between tmpfs and a traditional
> RAM disk. Someone posted an interesting link about this topic, IIRC in
> this very thread.

But IIUC, on a linux system that's been up for a while, with moderate
usage, pretty much all available memory should be 'used', as it will be
used for disk cache if not needed by applications.  So if the tmpfs
isn't reserving the full 1GB, shouldn't that memory be 'used' in the
output of 'free'?

Celejar
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