memory fragmentation issues in 1.2?
burton at tailrank.com
Wed Dec 6 22:20:04 UTC 2006
yeah.... swappiness is an evil little hidden secret...
For servers your best bet is to turn it off...
On 12/6/06, Paul T <pault12345 at yahoo.com> wrote:
> Turn off the OOM killer and see what happens?
> If you are running Linux, you might be surprised with
> the behaviour of it's memory manager on memcached node
> dedicated to memcached.
> By the way - univca (that does many things what
> memecached does) is using standard malloc with no
> pooling, runs for months, serves billions of hits and
> never got any 'memory fragmentation' issues.
> If you see the Linux box 'freezing' - check out Linux
> 'swappiness' parameter, the default setting of that
> parameter makes no sense when running something like
> dedicated memcached node, you don't want it to swap. I
> think that parameter is what caused the infamous
> linux swapping and 'memory fragmentation' myth in the
> first place.
> PS. In the absense of a test that can cleary reproduce
> a 'memory fragmentation' effect I suggest to call the
> 'memory fragmentation' and urban legend.
> --- George Schlossnagle <george at omniti.com> wrote:
> > Hi,
> > I'm seeing some weird behavior on my memcached 1.2
> > instances. Overtime
> > the RSS of my processess is growing and growing. I
> > start out at around
> > 800M (my configured memory size), and it
> > monotonically grows (over a
> > period of a couple weeks) until it is over double
> > that size and gets
> > killed by the OOM killer.
> > Trying to duplicate this behavior under valgrind
> > hasn't been very
> > fruitful, which makes me suspect it's system memory
> > fragmentation.
> > Has anyone else seen this sort of behaviour? Is
> > there some likely EBKAC
> > that I might be engaging in that could cause this?
> > I have some ideas
> > for working around this, but I'd much rather just be
> > told I'm stupid. :)
> > George
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