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Used shared backing array for Msg.Copy 

If you have a system with large amounts of copies, these slice
allocations start stacking up. Use a shared slice and then subslice
them with a cap limit so that append works properly.

Also, add a benchmark and test for Msg.Copy

Benchcmp:
benchmark         old ns/op     new ns/op     delta
BenchmarkCopy     1880          1672          -11.06%

benchmark         old allocs     new allocs     delta
BenchmarkCopy     13             11             -15.38%

benchmark         old bytes     new bytes     delta
BenchmarkCopy     528           528           +0.00%
This commit is contained in:
Daniel Morsing 2015-02-05 13:07:07 +00:00
parent dfa09b604c
commit a4af4dd14e
2 changed files with 57 additions and 6 deletions
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42
dns_test.go
View File

@ -510,6 +510,48 @@ func TestCopy(t *testing.T) {
}
}
func TestMsgCopy(t *testing.T) {
m := new(Msg)
m.SetQuestion("miek.nl.", TypeA)
rr, _ := NewRR("miek.nl. 2311 IN A 127.0.0.1")
m.Answer = []RR{rr}
rr, _ = NewRR("miek.nl. 2311 IN NS 127.0.0.1")
m.Ns = []RR{rr}
m1 := m.Copy()
if m.String() != m1.String() {
t.Fatalf("Msg.Copy() failed %s != %s", m.String(), m1.String())
}
m1.Answer[0], _ = NewRR("somethingelse.nl. 2311 IN A 127.0.0.1")
if m.String() == m1.String() {
t.Fatalf("Msg.Copy() failed; change to copy changed template %s", m.String())
}
rr, _ = NewRR("miek.nl. 2311 IN A 127.0.0.2")
m1.Answer = append(m1.Answer, rr)
if m1.Ns[0].String() == m1.Answer[1].String() {
t.Fatalf("Msg.Copy() failed; append changed underlying array %s", m1.Ns[0].String())
}
}
func BenchmarkCopy(b *testing.B) {
b.ReportAllocs()
m := new(Msg)
m.SetQuestion("miek.nl.", TypeA)
rr, _ := NewRR("miek.nl. 2311 IN A 127.0.0.1")
m.Answer = []RR{rr}
rr, _ = NewRR("miek.nl. 2311 IN NS 127.0.0.1")
m.Ns = []RR{rr}
rr, _ = NewRR("miek.nl. 2311 IN A 127.0.0.1")
m.Extra = []RR{rr}
b.ResetTimer()
for i := 0; i < b.N; i++ {
m.Copy()
}
}
func TestPackIPSECKEY(t *testing.T) {
tests := []string{
"38.2.0.192.in-addr.arpa. 7200 IN IPSECKEY ( 10 1 2 192.0.2.38 AQNRU3mG7TVTO2BkR47usntb102uFJtugbo6BSGvgqt4AQ== )",

21
msg.go
View File

@ -1912,25 +1912,34 @@ func (dns *Msg) Copy() *Msg {
copy(r1.Question, dns.Question) // TODO(miek): Question is an immutable value, ok to do a shallow-copy
}
rrArr := make([]RR, len(dns.Answer)+len(dns.Ns)+len(dns.Extra))
var rri int
if len(dns.Answer) > 0 {
r1.Answer = make([]RR, len(dns.Answer))
rrbegin := rri
for i := 0; i < len(dns.Answer); i++ {
r1.Answer[i] = dns.Answer[i].copy()
rrArr[rri] = dns.Answer[i].copy()
rri++
}
r1.Answer = rrArr[rrbegin:rri:rri]
}
if len(dns.Ns) > 0 {
r1.Ns = make([]RR, len(dns.Ns))
rrbegin := rri
for i := 0; i < len(dns.Ns); i++ {
r1.Ns[i] = dns.Ns[i].copy()
rrArr[rri] = dns.Ns[i].copy()
rri++
}
r1.Ns = rrArr[rrbegin:rri:rri]
}
if len(dns.Extra) > 0 {
r1.Extra = make([]RR, len(dns.Extra))
rrbegin := rri
for i := 0; i < len(dns.Extra); i++ {
r1.Extra[i] = dns.Extra[i].copy()
rrArr[rri] = dns.Extra[i].copy()
rri++
}
r1.Extra = rrArr[rrbegin:rri:rri]
}
return r1