runtime: failed to decommit pages on Windows

[dvyukov]

The following program crash on windows/386:

package main

import (
    "runtime/debug"
)

func main() {
    n := 350000
    buffs := make(chan []byte, n)
    for i := 0; i < n; i++ {
        buffs <- make([]byte, 1500)
    }
    for i := 0; i < n; i++ {
        <-buffs
    }
    debug.FreeOSMemory()
}


verified on revision +88ac7297d2fa Thu Jan 02 21:01:18 2014 +1100 windows/amd64

[dvyukov]

Comment 1:

The crash report:
fatal error: runtime: failed to decommit pages
goroutine 1 [running]:
runtime.throw(0x58cba0)
        C:/src/go/src/pkg/runtime/panic.c:462 +0x67 fp=0x2626d4
runtime.SysUnused(0x42960000, 0x2800000)
        C:/src/go/src/pkg/runtime/mem_windows.c:39 +0x62 fp=0x2626f0
scavengelist(0x59ffe4, 0xffffffff, 0x0, 0x0, 0x0)
        C:/src/go/src/pkg/runtime/mheap.c:405 +0xc2 fp=0x262708
scavenge(0xffffffff, 0xffffffff, 0x0, 0x0, 0x0)
        C:/src/go/src/pkg/runtime/mheap.c:422 +0xbd fp=0x262748
runtime/debug.freeOSMemory()
        C:/src/go/src/pkg/runtime/mheap.c:491 +0x62 fp=0x262760
runtime/debug.FreeOSMemory()
        C:/src/go/src/pkg/runtime/debug/garbage.go:102 +0x1d fp=0x262764
main.main()
        C:/src/tmp/mem.go:16 +0xe6 fp=0x262798
runtime.main()
        C:/src/go/src/pkg/runtime/proc.c:220 +0x10c fp=0x2627cc
runtime.goexit()
        C:/src/go/src/pkg/runtime/proc.c:1394 fp=0x2627d0
exit status 2

[dvyukov]

Comment 2:

I guess that's because we call VirtualFree on a region that spans several
VirtualAllocs's. We've merged several spans that come from separate VirtialAlloc's, and
then call single VirtualFree on whole range...

[dvyukov]

Comment 3:

Not sure what to do w/o significantly complicating runtime spans logic...

[alexbrainman]

Comment 4:

We don't have choice, we have to fix it. That is how Windows works.
Alex

[rsc]

Comment 5:

If VirtualFree fails on the whole region, try a smaller region.
byte *p;
uintptr m;
p = v;
while(n > 0) {
    for(m = n; m >= 4096; m /= 2) {
        if(runtime·stdcall(runtime·VirtualFree, 3, v, n, (uintptr)MEM_DECOMMIT) != nil)
            break;
    }
    if(m < 4096)
        runtime·throw("runtime: failed to decommit pages");
    p += m;
    n -= m;
}

[gopherbot]

Comment 7:

CL https://golang.org/cl/96300046 mentions this issue.

[rsc]

Comment 8:

This issue was closed by revision 30b8af9.

Status changed to Fixed.