On Wednesday 06 April 2016, Patrick Shanahan wrote:
> * Ruediger Meier <sweet_...@gmx.de> [04-06-16 13:07]:
> > On Wednesday 06 April 2016, Patrick Shanahan wrote:
> > > * Ruediger Meier <sweet_...@gmx.de> [04-06-16 10:45]:
> > > > Hi,
> > > >
> > > > Since a few weeks I see nscd running crazy on 13.1, like this
> > > >
> > > > USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+
> > > > COMMAND nscd      20   0 5265008 1.626g    652 S 0.000 5.185
> > > > 0:30.32 nscd
> > > >
> > > > I guess 1.6G would be enough to cache all existing zones
> > > > worldwide. What could be the problem?
> > >
> > > odd, mine has been up 261 days and:
> >
> > Could you show me your stats? I wonder if you have some reasonable
> > cache hit rates.
> > $ nscd -g
>
> nscd configuration:
>
>               0  server debug level
>  42d  3h 27m 41s  server runtime

So it was restarted during uptime. Because of libc update, or crash?

> passwd cache:
>               [...]
>               3  cache hits on positive entries
>               0% cache hit rate

> group cache:
>               [...]
>              13  cache hits on positive entries
>               0% cache hit rate
>
> hosts cache:
>               [...]
>             692  cache hits on positive entries
>               5% cache hit rate

> services cache:
>               [...]
>               1  cache hits on positive entries
>               3  cache hits on negative entries
>               0% cache hit rate

>
> netgroup cache:
>               [...]
>               0  cache hits on positive entries
>               0% cache hit rate


Only the host cache has at least 5% cache hit rate. Better than nothing? 
Absolute just 692 times within 42 days a minor speed-up to safe a few 
milliseconds. I wonder if it's really worth to run that buggy nscd at 
all. On my machines I've found none with a cache hit rate more than 0%, 
like Carlos' machine.

BTW the host cache is IMO the most dangerous one because it caches for 
600s per default and AFAIR ignores the domain specific TTL which comes 
from the name server. For example Google domains have usually only 300s 
TTL and I guess for a good reason (failover setup, whatever).

Other distros (Ubuntu) are using a real local DNS caching server on each 
machine which respects the DNS protocol. If you have one caching DNS 
server in your LAN (any usual router does that) then you probaly don't 
need neither nscd nor local DNS server.

cu,
Rudi
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