Closed
Description
I'm using Ipv4Addrs as keys in a BtreeMap. I have to look up the map ~15 million times per second (10G ethernet line rate).
Ipv4Addr cmp() compiles to this on my system (linux x86-64, rustc 1.10.0-nightly (476fe6e 2016-05-21))
0000000000051f10 <_ZN52_$LT$net..ip..Ipv4Addr$u20$as$u20$core..cmp..Ord$GT$3cmp17h39591ec7a18c4b02E>:
51f10: 50 push %rax
51f11: c7 44 24 04 1d 1d 1d movl $0x1d1d1d1d,0x4(%rsp)
51f18: 1d
51f19: c7 04 24 1d 1d 1d 1d movl $0x1d1d1d1d,(%rsp)
51f20: 8b 07 mov (%rdi),%eax
51f22: 89 c1 mov %eax,%ecx
51f24: 88 44 24 04 mov %al,0x4(%rsp)
51f28: 88 64 24 05 mov %ah,0x5(%rsp)
51f2c: c1 e8 10 shr $0x10,%eax
51f2f: c1 e9 18 shr $0x18,%ecx
51f32: 88 44 24 06 mov %al,0x6(%rsp)
51f36: 88 4c 24 07 mov %cl,0x7(%rsp)
51f3a: 8b 06 mov (%rsi),%eax
51f3c: 89 c1 mov %eax,%ecx
51f3e: 88 04 24 mov %al,(%rsp)
51f41: 88 64 24 01 mov %ah,0x1(%rsp)
51f45: c1 e8 10 shr $0x10,%eax
51f48: c1 e9 18 shr $0x18,%ecx
51f4b: 88 44 24 02 mov %al,0x2(%rsp)
51f4f: 88 4c 24 03 mov %cl,0x3(%rsp)
51f53: 48 8d 7c 24 04 lea 0x4(%rsp),%rdi
51f58: 48 8d 34 24 lea (%rsp),%rsi
51f5c: ba 04 00 00 00 mov $0x4,%edx
51f61: e8 0a 17 fc ff callq 13670 <memcmp@plt>
51f66: 89 c1 mov %eax,%ecx
51f68: 31 c0 xor %eax,%eax
51f6a: 85 c9 test %ecx,%ecx
51f6c: b1 ff mov $0xff,%cl
51f6e: 78 02 js 51f72 <_ZN52_$LT$net..ip..Ipv4Addr$u20$as$u20$core..cmp..Ord$GT$3cmp17h39591ec7a18c4b02E+0x62>
51f70: b1 01 mov $0x1,%cl
51f72: 74 02 je 51f76 <_ZN52_$LT$net..ip..Ipv4Addr$u20$as$u20$core..cmp..Ord$GT$3cmp17h39591ec7a18c4b02E+0x66>
51f74: 88 c8 mov %cl,%al
51f76: 59 pop %rcx
Which seems kinda inefficient for a thing which is basically u32.
I guess part of the reason is the implementation which converts it to an array(!) first.
I copied the definition and implemented Ord like this:
impl Ord for Ipv4Addr2 {
fn cmp(&self, other: &Self) -> cmp::Ordering {
return Ord::cmp(&ntoh(self.inner.s_addr), &ntoh(other.inner.s_addr));
}
}
It's about 10 times faster on my benchmark.
rustc 1.10.0-nightly (476fe6eef 2016-05-21)
binary: rustc
commit-hash: 476fe6eefe17db91ff7a60aab34aa67a0a750a18
commit-date: 2016-05-21
host: x86_64-unknown-linux-gnu
release: 1.10.0-nightly