[CentOS] Swap memory: I can't reconcile this stuff.
William L. Maltby
BillsCentOS at triad.rr.com
Tue Jun 6 00:50:31 UTC 2006
On Mon, 2006-06-05 at 20:02 -0300, Rodrigo Barbosa wrote:
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> On Mon, Jun 05, 2006 at 06:45:10PM -0400, William L. Maltby wrote:
> ><snip>
> >
> > Mem: 775708k total, 764752k used, 10956k free, 60780k buffers
> > Swap: 1572856k total, 160k used, 1572696k free, 377324k cached
> >
> > PID VIRT RES SHR %MEM SWAP COMMAND
> > 24729 127m 32m 15m 4.3 94m evolution
> > 3409 97220 5268 4304 0.7 89m evolution-data-
> > 2851 115m 36m 7120 4.8 79m X
> > 3359 19904 6128 5316 0.8 13m gnome-volume-ma
> (...)
> > 3355 14768 7524 5984 1.0 7244 metacity
> > 7182 10328 3436 2280 0.4 6892 sendmail
> > 18501 11080 4248 1912 0.5 6832 cupsd
> >
> > Note that the summary line says 160k of swap is used. The man pages say
> > the summary and the details under "SWAP" are both reported in "k". No
> > mention of "m" is made, I presume that it means "megabytes"?
> > <snip>
> > Now, if I treat all those numbers ending in "m" as megabytes, it doesn't
> > take long to see that I've been lied to somewhere along the way. Or
> > alternatively, I'm dense and "Just Don't Get It" (TM).
> >
> > Any help?
>
> I can see two possible explanations for this. Maybe both in conjunction.
>
> One is that you get getting multiple entries for the same processes,
> but different threads. That used to be the way of it up until .. humm,
> not sure ... 2.4, I guess. Not sure exactly how it works these days. I would
> have to check.
>
> The other is the overcommit kernel feature. It is possible the kernel
> is overcommiting memory, and thus showing more than it really in
> use.
>
> One last thing possible (just thought about it) is that top is adding
> more than one namespace to those totals. Maybe shared memory (/dev/shm ?).
> Or any other possible namespace.
>
> I agree it does seem odd, and I have seen this kind of stuff happening
> before. Once I started hunting it down, and found the reason for it.
> It was some time ago (2.2 ? 2.4 ? Not sure), so I'm reasonably sure
> it is not the same reason these days. But I hope I gave you are
> least some pointers for where to start looking.
Would I be correct if I summarized as "Looks like a bug, and possibly a
regression that you had seen before"? I think then I'll first start by
seeing if there is an open bug somewhere. I hate having to chase code
right now as I'm trying to improve my knowledge and use of sendmail,
DNS, ... and a whole host of other things that flew by me over the
years. <*sigh*>
Anyhow, thanks for getting back to me. I'm going to try to work
investigation of this in with the other things I've got going.
> - --
> Rodrigo Barbosa <rodrigob at suespammers.org>
> <snip sig stuff>
--
Bill
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