Local perf test

[miekg]

This is on my laptop (4 core, 8 GB). Go 1.8.

Using the just commited utils in the "local-perf" directory.

(pprof) top10   
0.09s of 7.06s total ( 1.27%)
Dropped 108 nodes (cum <= 0.04s)
Showing top 10 nodes out of 165 (cum >= 1.53s)
      flat  flat%   sum%        cum   cum%
         0     0%     0%      5.24s 74.22%  runtime.goexit
         0     0%     0%      2.95s 41.78%  github.com/miekg/dns.(*Server).serve
         0     0%     0%      2.46s 34.84%  github.com/coredns/coredns/core/dnsserver.(*Server).ServePacket.func1
         0     0%     0%      2.46s 34.84%  github.com/miekg/dns.HandlerFunc.ServeDNS
     0.04s  0.57%  0.57%      2.45s 34.70%  github.com/coredns/coredns/core/dnsserver.(*Server).ServeDNS
         0     0%  0.57%      2.33s 33.00%  github.com/coredns/coredns/middleware/whoami.(*Whoami).ServeDNS
     0.04s  0.57%  1.13%      2.33s 33.00%  github.com/coredns/coredns/middleware/whoami.Whoami.ServeDNS
     0.01s  0.14%  1.27%      1.56s 22.10%  github.com/miekg/dns.(*response).WriteMsg
         0     0%  1.27%      1.53s 21.67%  github.com/coredns/coredns/core/dnsserver.(*Server).ServePacket
         0     0%  1.27%      1.53s 21.67%  github.com/mholt/caddy.startServers.func1

Corefile included in that repo. CoreDNS is running with: ./coredns -conf ~/git/coredns/perf-tests/local-perf/Corefile

profile attached. pprof.coredns.localhost:6053.samples.cpu.001.pb.gz