Add madvise() after mmap().
This commit advises the mmapped data file to use MADV_RANDOM to avoid
readahead. This can provide a performance boost to Bolt databases that
are larger than memory by avoiding unnecessary disk i/o.
Ben Johnson
8 years ago
| 62 | 62 | return err |
| 63 | 63 | } |
| 64 | 64 | |
| 65 | // Advise the kernel that the mmap is accessed randomly. | |
| 66 | if err := madvise(b, syscall.MADV_RANDOM); err != nil { | |
| 67 | return fmt.Errorf("madvise: %s", err) | |
| 68 | } | |
| 69 | ||
| 65 | 70 | // Save the original byte slice and convert to a byte array pointer. |
| 66 | 71 | db.dataref = b |
| 67 | 72 | db.data = (*[maxMapSize]byte)(unsafe.Pointer(&b[0])) |
| 83 | 88 | db.datasz = 0 |
| 84 | 89 | return err |
| 85 | 90 | } |
| 91 | ||
| 92 | // NOTE: This function is copied from stdlib because it is not available on darwin. | |
| 93 | func madvise(b []byte, advice int) (err error) { | |
| 94 | _, _, e1 := syscall.Syscall(syscall.SYS_MADVISE, uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)), uintptr(advice)) | |
| 95 | if e1 != 0 { | |
| 96 | err = e1 | |
| 97 | } | |
| 98 | return | |
| 99 | } | |