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Improve OpenBSD memory handling #77

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Improve OpenBSD memory handling #77

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e19fe5b
Sync struct uvmexp and bcachestats with OpenBSD 6.1
jasperla Jun 29, 2017
0e3fec1
Add better error handling for functions directly using kernel structures
jasperla Jun 30, 2017
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20 changes: 15 additions & 5 deletions sigar_openbsd.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ import "C"
//import "github.com/davecgh/go-spew/spew"

import (
"fmt"
"runtime"
"syscall"
"time"
Expand Down Expand Up @@ -240,30 +241,39 @@ func (self *Mem) Get() error {
// First we determine how much memory we'll need to pass later on (via `n`)
_, _, errno := syscall.Syscall6(syscall.SYS___SYSCTL, uintptr(unsafe.Pointer(&mib[0])), 2, 0, uintptr(unsafe.Pointer(&n)), 0, 0)
if errno != 0 || n == 0 {
return nil
return fmt.Errorf("Failed to prepare vm.uvmexp: %d", errno)
}

_, _, errno = syscall.Syscall6(syscall.SYS___SYSCTL, uintptr(unsafe.Pointer(&mib[0])), 2, uintptr(unsafe.Pointer(&uvmexp)), uintptr(unsafe.Pointer(&n)), 0, 0)
if errno != 0 || n == 0 {
return nil
return fmt.Errorf("Failed to query vm.uvmexp: %d", errno)
}

var bcachestats Bcachestats
mib3 := [3]int32{C.CTL_VFS, C.VFS_GENERIC, C.VFS_BCACHESTAT}
n = uintptr(0)
_, _, errno = syscall.Syscall6(syscall.SYS___SYSCTL, uintptr(unsafe.Pointer(&mib3[0])), 3, 0, uintptr(unsafe.Pointer(&n)), 0, 0)
if errno != 0 || n == 0 {
return nil
return fmt.Errorf("Failed to prepare vfs.generic.bcachestat: %d", errno)
}

_, _, errno = syscall.Syscall6(syscall.SYS___SYSCTL, uintptr(unsafe.Pointer(&mib3[0])), 3, uintptr(unsafe.Pointer(&bcachestats)), uintptr(unsafe.Pointer(&n)), 0, 0)
if errno != 0 || n == 0 {
return nil
return fmt.Errorf("Failed to query vfs.generic.bcachestat: %d", errno)
}

self.Total = uint64(uvmexp.npages) << uvmexp.pageshift
self.Used = uint64(uvmexp.npages-uvmexp.free) << uvmexp.pageshift
self.Free = uint64(uvmexp.free) << uvmexp.pageshift

// If the kernel interface changes we might silently return bogus
// data. So explicitly check for 0 total memory (check this late in
// the program flow as by now various kernel interfaces have been
// used. cf. https://github.com/elastic/gosigar/issues/72
if self.Total == 0 {
return fmt.Errorf("Invalid data: zero memory pages found")
}

self.ActualFree = self.Free + (uint64(bcachestats.numbufpages) << uvmexp.pageshift)
self.ActualUsed = self.Used - (uint64(bcachestats.numbufpages) << uvmexp.pageshift)

Expand All @@ -282,7 +292,7 @@ func (self *Swap) Get() error {

rnswap := C.swapctl(C.SWAP_STATS, unsafe.Pointer(&swdev[0]), nswap)
if rnswap == 0 {
return nil
return fmt.Errorf("Failed to call swapctl(2)")
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Will this return an error when a machine has 0 swap devices? The OpenBSD man page for swapctl(2) is somewhat ambiguous here, but my interpretation is that a return value of 0 is OK and -1 indicates failure.

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It won't return an error in such case; I've ran swapctl -d /dev/sd0b to remove my /dev/sd0b as a swap device and this conditional didn't get triggered.

}

for i := 0; i < int(nswap); i++ {
Expand Down