Tuning the nscd name cache daemon

I've been playing a bit with the nscd now and want to share some tips related to tuning the nscd.conf file.

To see how the DNS cache is doing, use nscd -g.

nscd configuration:

              0  server debug level
        26m 57s  server runtime
              5  current number of threads
             32  maximum number of threads
              0  number of times clients had to wait
            yes  paranoia mode enabled
           3600  restart internal

passwd cache:
             no  cache is enabled
[other zero output removed]
group cache:
             no  cache is enabled
[other zero output removed]

hosts cache:

            yes  cache is enabled
            yes  cache is persistent
            yes  cache is shared
            211  suggested size                       <====
         216064  total data pool size
           1144  used data pool size
           3600  seconds time to live for positive entries <====
             20  seconds time to live for negative entries
          66254  cache hits on positive entries
              0  cache hits on negative entries
            215  cache misses on positive entries
            150  cache misses on negative entries
             99% cache hit rate                       <====
              7  current number of cached values      <====
             28  maximum number of cached values      <====
              3  maximum chain length searched
              0  number of delays on rdlock
              0  number of delays on wrlock
              0  memory allocations failed
            yes  check /etc/hosts for changes

Check the cache hit rate.
If it's low, then if the 'current number of cached values' (here:7) is near the 'suggested-size' parameter (here:211), it means your cache is too small. Entries are being cached faster than they're being reused.
If 'maximum number of cached values' is near the suggested-size, there are periods when your system is caching a lot more than usual (check the current value) and you may need to tweak the suggested-size to slightly larger.
Also, the time nscd retains cache entries will be of influence on performance (here:3600 seconds). A lower value means an entry is cached briefly before flushing it and rerequesting a host from the DNS server. A high value means an entry can get stale, but more so for passwords than for hostnames. Nonetheless, lowering the value could free up the cache for new recent hostnames, instead of keeping old entries in the cache.
Any non zero value for 'memory allocations failed' may indicate your data pool is too small or the persistent store is running out of space. Or your system may simply be low on memory.
If you have some 'number of times clients had to wait', you could increase the number of threads. However, creating more threads means you'll handle more requests and your statistics will change. Both for the better or the worse! So recheck the stats afterward!

If you change parameters, it may be wise to clear (invalidate) the (persistent) cache using nscd -i {passwd,group,hosts}