> On Tue, 2009-04-07 at 13:11 +0100, Nick Lunt wrote:
> > Hi Tom
> >
> > yes it's running 64Bit ;)
> >
> > We have turned swap off for the time being...
> >
> > [r...@findb ~]# free -lom
> > total used free shared buffers
> > cached
> > Mem: 64453 64147 306 0 123
> > 11782
> > Low: 64453 64147 306
> > High: 0 0 0
> > Swap: 0 0 0
>
> Does removing swap actually eliminates the problem? I'm a little
> surprised since kswapd really does more than just swapping, it
> basically
> scans memory whenever the number of free pages drops below a given
> threshold looking for memory to free. Swapping is just one way it can
> free memory, it can also shrink the buffer and page cache, and find
> discardable pages. That being said, it's possible that removing swap
> may change the dynamic of your systems memory management in others
ways
> that will keep it from happening.
>
> I don't have any 64GB systems, but we have a couple of 32GB systems
> running Oracle and have never seen anything like this. It does seem
> like your free pages are very low while your cache is over 11GB. Does
> this have something to do with the 200,000 files you were talking
> about.
> Is whatever your doing with those causing continuous memory pressure
by
> dirtying the cache thus meaning that kswapd is constantly waking
trying
> to find memory to free?
>
> Are you using huge pages with your Oracle setup?
>
Hi Tom
I have just enabled a 2GB swap partition as a safety net.
We have not tried running without swap before so I do not know if this
would fix the problem.
We are using huge pages
vm.nr_hugepages=15363
I aren't sure what the cached column report by free means to be honest,
could you give me a quick rundown ?
Here's how free looks with the 2GB swap device added:
[r...@findb ~]# free
total used free shared buffers
cached
Mem: 66000400 65692088 308312 0 159324
15332996
-/+ buffers/cache: 50199768 15800632
Swap: 2097144 724 2096420
And here's a quick sar -r output
[r...@findb ~]# sar -r 3 5
Linux 2.6.18-92.el5 (findb.wales.nhs.uk) 04/07/2009
03:17:10 PM kbmemfree kbmemused %memused kbbuffers kbcached kbswpfree
kbswpused %swpused kbswpcad
03:17:13 PM 305180 65695220 99.54 157768 15277388 2096420
724 0.03 0
03:17:16 PM 306128 65694272 99.54 157644 15285480 2096420
724 0.03 0
03:17:19 PM 300444 65699956 99.54 157284 15284780 2096420
724 0.03 0
03:17:22 PM 306880 65693520 99.54 156100 15283400 2096420
724 0.03 0
03:17:25 PM 300152 65700248 99.55 155908 15285424 2096420
724 0.03 0
Average: 303757 65696643 99.54 156941 15283294 2096420
724 0.03 0
If any of this rings any bells please let me know :)
Thanks
Nick.
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