5 ms·

This isn't my patch, so I can't speak to the specifics of it. Also, it isn't for gccgo, but the gc compiler.

• lobster_johnson 14y ago
  That's too bad. Hopefully someone will improve `gccgo` as well. I actually started out experimenting with Go using the `gc` compiler, and found performance (basically manipulating large arrays sequentially) atrocious. Moving to `gccgo` improved performance four-fold, making my unoptimized Go test code in some cases faster than my unoptimized C test code.
  • luriel 14y ago
    How long ago was that? The gc compilers have seen lots of improvement recently, and more will be merged soon. Also, if the problem is so pathological, it might be worth filling an issue.
    • lobster_johnson 14y ago
      Go 1.0.2, which is the newest stable release. I will see if I have some extra time to file a report. Slightly off topic (but relevant to my comment above), do you know why this: func TraverseInline() { var ints := make([]int, N) for i := range ints { sum += i } } should be slower than: func TraverseArray(ints []int) int { sum := 0 for i := range ints { sum += i } return sum } func TraverseWithFunc() { var ints := make([]int, N) sum := TraverseArray(ints) } Seeing a huge difference here. With an array of 300000000 ints, TraverseInline() takes about 750ms, whereas TraverseWithFunc() takes 394ms. With gccgo (GCC 4.7.1), the different is much slighter, but there's still a difference: 196ms compared to 172ms. (These are best-case figures, I'm doing lots of loops.) Go is compiled, not JIT, so I don't see why a function should offer better performance.
      • agentS 14y ago
        Not sure why the difference in performance between function and non-function, particularly considering this looks inline-able. 2 theories on why gcc is doing better. Maybe its unrolling the loop, and avoids a bunch of jumps. Alternatively, it could be using SSE, but this theory is a much less likely, because I would expect it to be 4 times faster not twice as fast. gc doesn't use SSE instructions yet.
      • genbattle 14y ago
        I don't have any immediate insight for the difference in performance you're seeing (my hunch is that it's to do with where and how memory is being allocated), but I would suggest you ask about it on the Go-Nuts mailing list: https://groups.google.com/forum/?fromgroups#!forum/golang-nuts https://groups.google.com/forum/?fromgroups#!forum/golang-nu... The Go authors should be very receptive and informative on such an issue.
      • dmit 14y ago
        I'm not seeing any difference between the two functions using the 1.0.2 x64 gc compiler. Here's the code I used (slightly modified to compile): http://play.golang.org/p/gcf0BOGncQ http://play.golang.org/p/gcf0BOGncQ For more complex functions, you could try profiling using the runtime/pprof package. More info here: http://blog.golang.org/2011/06/profiling-go-programs.html http://blog.golang.org/2011/06/profiling-go-programs.html If you want to dig deeper and are not averse to assembly, you can pass -gcflags -S to 'go build' and see the compiler output. Here's what I got for the above code: --- prog list "TraverseInline" --- 0000 (/tmp/tmp.rkM3kSJ6Hd/trav.go:10) TEXT TraverseInline+0(SB),$40-8 0001 (/tmp/tmp.rkM3kSJ6Hd/trav.go:11) MOVQ $type.[]int+0(SB),(SP) 0002 (/tmp/tmp.rkM3kSJ6Hd/trav.go:11) MOVQ $300000000,8(SP) 0003 (/tmp/tmp.rkM3kSJ6Hd/trav.go:11) MOVQ $300000000,16(SP) 0004 (/tmp/tmp.rkM3kSJ6Hd/trav.go:11) CALL ,runtime.makeslice+0(SB) 0005 (/tmp/tmp.rkM3kSJ6Hd/trav.go:11) MOVQ 24(SP),BX 0006 (/tmp/tmp.rkM3kSJ6Hd/trav.go:11) MOVL 32(SP),SI 0007 (/tmp/tmp.rkM3kSJ6Hd/trav.go:11) MOVL 36(SP),BX 0008 (/tmp/tmp.rkM3kSJ6Hd/trav.go:12) MOVL $0,DX 0009 (/tmp/tmp.rkM3kSJ6Hd/trav.go:13) MOVL $0,AX 0010 (/tmp/tmp.rkM3kSJ6Hd/trav.go:13) JMP ,12 0011 (/tmp/tmp.rkM3kSJ6Hd/trav.go:13) INCL ,AX 0012 (/tmp/tmp.rkM3kSJ6Hd/trav.go:13) CMPL AX,SI 0013 (/tmp/tmp.rkM3kSJ6Hd/trav.go:13) JGE ,16 0014 (/tmp/tmp.rkM3kSJ6Hd/trav.go:14) ADDL AX,DX 0015 (/tmp/tmp.rkM3kSJ6Hd/trav.go:13) JMP ,11 0016 (/tmp/tmp.rkM3kSJ6Hd/trav.go:16) MOVL DX,.noname+0(FP) 0017 (/tmp/tmp.rkM3kSJ6Hd/trav.go:16) RET , --- prog list "TraverseArray" --- 0018 (/tmp/tmp.rkM3kSJ6Hd/trav.go:19) TEXT TraverseArray+0(SB),$0-24 0019 (/tmp/tmp.rkM3kSJ6Hd/trav.go:20) MOVL $0,DX 0020 (/tmp/tmp.rkM3kSJ6Hd/trav.go:21) MOVL $0,AX 0021 (/tmp/tmp.rkM3kSJ6Hd/trav.go:21) MOVL ints+8(FP),SI 0022 (/tmp/tmp.rkM3kSJ6Hd/trav.go:21) JMP ,24 0023 (/tmp/tmp.rkM3kSJ6Hd/trav.go:21) INCL ,AX 0024 (/tmp/tmp.rkM3kSJ6Hd/trav.go:21) CMPL AX,SI 0025 (/tmp/tmp.rkM3kSJ6Hd/trav.go:21) JGE ,28 0026 (/tmp/tmp.rkM3kSJ6Hd/trav.go:22) ADDL AX,DX 0027 (/tmp/tmp.rkM3kSJ6Hd/trav.go:21) JMP ,23 0028 (/tmp/tmp.rkM3kSJ6Hd/trav.go:24) MOVL DX,.noname+16(FP) 0029 (/tmp/tmp.rkM3kSJ6Hd/trav.go:24) RET , --- prog list "TraverseWithFunc" --- 0030 (/tmp/tmp.rkM3kSJ6Hd/trav.go:27) TEXT TraverseWithFunc+0(SB),$40-8 0031 (/tmp/tmp.rkM3kSJ6Hd/trav.go:28) MOVQ $type.[]int+0(SB),(SP) 0032 (/tmp/tmp.rkM3kSJ6Hd/trav.go:28) MOVQ $300000000,8(SP) 0033 (/tmp/tmp.rkM3kSJ6Hd/trav.go:28) MOVQ $300000000,16(SP) 0034 (/tmp/tmp.rkM3kSJ6Hd/trav.go:28) CALL ,runtime.makeslice+0(SB) 0035 (/tmp/tmp.rkM3kSJ6Hd/trav.go:28) MOVQ 24(SP),DX 0036 (/tmp/tmp.rkM3kSJ6Hd/trav.go:28) MOVL 32(SP),CX 0037 (/tmp/tmp.rkM3kSJ6Hd/trav.go:28) MOVL 36(SP),AX 0038 (/tmp/tmp.rkM3kSJ6Hd/trav.go:29) LEAQ (SP),BX 0039 (/tmp/tmp.rkM3kSJ6Hd/trav.go:29) MOVQ DX,(BX) 0040 (/tmp/tmp.rkM3kSJ6Hd/trav.go:29) MOVL CX,8(BX) 0041 (/tmp/tmp.rkM3kSJ6Hd/trav.go:29) MOVL AX,12(BX) 0042 (/tmp/tmp.rkM3kSJ6Hd/trav.go:29) CALL ,TraverseArray+0(SB) 0043 (/tmp/tmp.rkM3kSJ6Hd/trav.go:29) MOVL 16(SP),AX 0044 (/tmp/tmp.rkM3kSJ6Hd/trav.go:30) MOVL AX,.noname+0(FP) 0045 (/tmp/tmp.rkM3kSJ6Hd/trav.go:30) RET ,