linux-kernel - Re: top lies ?

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Message-Id: <200711131038.26436.a1426z@gawab.com>
Date:	Tue, 13 Nov 2007 10:38:26 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	"Balbir Singh" <balbir@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: top lies ?

Balbir Singh wrote:
> On Nov 13, 2007 12:38 PM, Al Boldi <a1426z@...ab.com> wrote:
> > kloczek wrote:
> > > Some data showed by top command looks like completly trashed.
> > > Fragment from top output:
> > >
> > > Mem:   2075784k total,  2053352k used,    22432k free,    19260k
> > > buffers Swap:  2096472k total,      136k used,  2096336k free, 
> > > 1335080k cached
> > >
> > >    PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  SWAP nFLT WCHAN     COMMAND
> > >  14515 mysql     20   0 1837m 563m 4132 S   39  27.8 27:14.20 1.2g   18 -         mysqld
> > >
> > > How it is possible that swap ussage is 136k and swapped out portion of
> > > (in this case) mysqld process is 1.2g ?
> >
> > Welcome to OverCommit, aka OOM-nirvana.
> >
> > Try this:
> > # echo 2 > /proc/sys/vm/overcommit_memory
> > # echo 0 > /proc/sys/vm/overcommit_ratio
> >
> > But make sure you have enough swap.
> >
> >
> > Thanks!
>
> The swap cache looks pretty big, may be top is including that data
> while reporting swap usage.

I don't think so.  top reports correctly, it's the VM that is lying.
I guess you can tell what happens when push comes to shove...


Thanks!

--
Al

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