Preallocate the sources slice in MultiUpstreams.Provision and the
netAddrs slice in UpstreamResolver.ParseAddresses now that their final
lengths are known, avoiding the intermediate append regrowth
allocations. For a 4-address resolver this reduces ParseAddresses from
11 to 9 allocs/op and 528 to 384 B/op; the benefit scales with the
number of sources/addresses.
| before | after |
| sec/op | sec/op vs base |
UpstreamResolverParseAddresses-8 | 2.289µ |1.946µ ~ (p=0.165) noisy |
B/op: 528 → 384 -27.27% (p=0.000)
allocs/op: 11 → 9 -18.18% (p=0.000)
Adds BenchmarkUpstreamResolverParseAddresses as per policy.
Julien Voisin