Cached Swap?

[Matthew Miller]

On Mon, Mar 05, 2007 at 10:31:42AM -0600, Mike McCarty wrote:
> Ok, I asked before, what can "cached swap" possibly be, besides
> an oxymoron. I have this line from top:
> Swap:   524120k total,   133360k used,   390760k free,    61148k cached
> I got the reply that this is not "cached swap", but just "cache".

That is correct.

> However,
> # cat /proc/meminfo | head
> MemTotal:       248088 kB
> MemFree:          7828 kB
> Buffers:          4612 kB
> Cached:          58268 kB
> SwapCached:      66212 kB
> Active:         181632 kB
> Inactive:        10964 kB
> HighTotal:           0 kB
> HighFree:            0 kB
> LowTotal:       248088 kB
> 
> So I ask: What is SwapCached?

This is documented in filesystems/proc.txt (in the kernel-doc package).

That line has nothing to do with the "cached" entry (and isn't shown by
top). It's memory that was swapped out, and is now back in RAM but is also
still not erased from the swap disk (handly in case it needs to be put back
soon). It's not generally an interesting number.



-- 
Matthew Miller           mattdm at mattdm.org          <http://mattdm.org/>
Boston University Linux      ------>              <http://linux.bu.edu/>