On Tue, 2008-04-22 at 00:38 +0300, Oded Arbel wrote:
> Hi List
>
>
> One of my servers is acting very strangely memory wise - it has 4GB of
> memory and it is always full, and I don't mean in the "not a lot of free
> memory" kind of full, but in the "application memory takes more then
> 3GB" kind of full.
>
> I ran a simple script to compare how many resident memory PS reports
> compared to what free reports is being used for stuff other then cache
> and buffers, and I got these interesting results:
>
> This is a normal which is very loaded and by right - it has a java
> application which is set to 2GB heap and uses it just fine:
>
> # ps auwx | perl -nle 'split/\s+/; $sum += $_[5]; END { print "sum:
> $sum"; }'; free
> sum: 3158192
> total used free shared buffers
> cached
> Mem: 4063412 4029396 34016 0 20016
> 360368
> -/+ buffers/cache: 3649012 414400
> Swap: 4194296 354188 3840108
>
> So we can see PS reports 3.1GB is used by applications and free reports
> 3.6GB of used memory (except buffers and cache). so I'm missing about
> half a gig, but I don't mind that much.
>
> Here is the broken server:
>
> # ps auwx | perl -nle 'split/\s+/; $sum += $_[5]; END { print "sum:
> $sum"; }'; free
> sum: 1367356
> total used free shared buffers
> cached
> Mem: 4063412 4038212 25200 0 35604
> 726268
> -/+ buffers/cache: 3276340 787072
> Swap: 4194296 656508 3537788
>
> which is mind boggling - there's a 2GB difference, about half my total
> amount of memory! Where did all my memory gone too ?
>
> Now that server is also constantly spends tons of time in kswapd and on
> IO - thrashing if you want and I'm not sure if its a symptom or the
> cause.
>
> Do note that both are production servers and I can't really restart them
> or anything, even taking down services is a long and annoying process.
I just noticed something else - both servers are running MySQL, and I'm
using htop (instead of top) to look at processes. Now in the "good
server" htop lists MySQL memory share as 8.5% and the numbers are
VIRT=615M and RES=329M , while in the "bad server" htop list MySQL as
using VIRT=1364M and RES=409M but lists it as only 3.8% of memory ?!?
both servers carry the same 4GB of physical memory and 4GB swap.
--
Oded
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