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At some point hitherto, Drew Taylor hath spake thusly:
> I'm running a kernel 2.4.2-2 (stock from RH 7.1) and am wondering what is 
> the difference between buffers and cached memory? 

My memory of the details is sketchy, but IIRC...

"cached" refers explicitly to buffer cache, i.e. disk blocks that the
kernel has placed in memory because either it has accessed them
recently, or expects to soon.  The kernel also buffers I/O and sets
aside some memory with which to do that.  "buffers" is, I believe,
the amount of memory set aside for that purpose.


On 2 May 2002 at 10:55, David Kramer wrote:

> On Thu, 2 May 2002, Drew Taylor wrote:
> 
> > [drew@nephi]$ cat /proc/meminfo
> >          total:    used:    free:  shared: buffers:  cached: 
> > Mem:  195735552 194052096  1683456        0 13651968 122585088
> > Swap: 205590528   290816 205299712
> > MemTotal:       191148 kB
> > MemFree:          1644 kB
> > MemShared:           0 kB
> 
[SNIP]
> Because of this, it may be hard to come up with a definitive number
> of "free memory".

Not entirely true.  Linux provides the free command, which outputs
basically the above info, with some minor differences:

$ free
             total       used       free     shared    buffers   cached
Mem:        126972     122324       4648          0      23956   37280
- -/+ buffers/cache:      61088      65884
Swap:       136512      55428      81084

The -/+ buffers line tells you how much (in theory) memory is really
used and/or free.  Note that in the above output, buffers + cache =
61236.  Add 4648 (from (mem,free)) to that, and you get the 65884 that
you find in (+/- buffers,free).  So that's the "real" amount of RAM
that's free.  Except that it isn't, because it's full of buffers.  :)


- -- 
Derek Martin               ddm@pizzashack.org    
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