diff options
Diffstat (limited to 'src/pkg/runtime/os_plan9.c')
| -rw-r--r-- | src/pkg/runtime/os_plan9.c | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/src/pkg/runtime/os_plan9.c b/src/pkg/runtime/os_plan9.c index cf3480deac..6da7c7ef52 100644 --- a/src/pkg/runtime/os_plan9.c +++ b/src/pkg/runtime/os_plan9.c @@ -146,6 +146,35 @@ runtime·usleep(uint32 µs) runtime·sleep(ms); } +#pragma textflag NOSPLIT +int64 +runtime·nanotime(void) +{ + static int32 fd = -1; + byte b[8]; + uint32 hi, lo; + + // As long as all goroutines share the same file + // descriptor table we can get away with using + // just a static fd. Without a lock the file can + // be opened twice but that's okay. + // + // Using /dev/bintime gives us a latency on the + // order of ten microseconds between two calls. + // + // The naïve implementation (without the cached + // file descriptor) is roughly four times slower + // in 9vx on a 2.16 GHz Intel Core 2 Duo. + + if(fd < 0 && (fd = runtime·open("/dev/bintime", OREAD|OCEXEC, 0)) < 0) + return 0; + if(runtime·pread(fd, b, sizeof b, 0) != sizeof b) + return 0; + hi = b[0]<<24 | b[1]<<16 | b[2]<<8 | b[3]; + lo = b[4]<<24 | b[5]<<16 | b[6]<<8 | b[7]; + return (int64)hi<<32 | (int64)lo; +} + void time·now(int64 sec, int32 nsec) { |