[CentOS] Swap memory: I can't reconcile this stuff.

Wed Jun 7 02:37:53 UTC 2006
Feizhou <feizhou at graffiti.net>

William L. Maltby wrote:
> On Tue, 2006-06-06 at 13:45 +0800, Feizhou wrote:
>> Sam Drinkard wrote:
>>>
>>> William L. Maltby wrote:
>>>
>>>> I need to look more into it, but before I start the long and arduous
>>>> "googling my life away" process, I figured someone might know the
>>>> answer. I've read the man pages several times and they didn't change!
>>>> :-(
>>>>
>>>> <snip>
> 
>> most of the 'swapped' data is probably sitting in the cache or buffers?
>>
>> Here is an example:
>>
>> https://bugzilla.redhat.com/bugzilla/attachment.cgi?id=129064
> 
> Thanks to the patience and efforts of all, Rodrigo, Les, Sam,
> Feizhou ... I think I've got a handle on this thing.
> 
> The only mistake was turning on "SWAP" in top.
> 
> I can see difficulty in programming to get a *meaningful* swap figure:
> that is, one that represents either real swapped memory, or its current
> needs or its potential maximum need. That assumes one can make the
> decision as to which to show.
> 
> Others already show (apparently) current swap (free, top's summary
> lines), so what could one put under the "SWAP" column? I now think that
> it was the maximum possible swap needed for each process, as you all
> suggested.

:)

> 
> Text shared from program segments and libraries, shared data, buffers,
> cache, parts already swapped, parts marked for swap but not committed
> yet,... What would show under the "swap top"? From a programming POV,
> showing anything but the virtual memory use could be complex and have a
> tight coupling to the VM implementation details, increasing maintenance
> for a little used data column too.
> 
> I am comfortable that "SWAP" only shows the simplest to obtain value and
> the only problem is that a better explanation is could be provided in
> the man pages for top.

Eh? I thought that problem kind of exists for all man pages!

> 
>> <snip sig stuff>
> 
> And we do know that a fix for the lock up in Sam's and my machine is
> apparently in the pipeline for U4.

If I was a paying customer....