diff options
| -rw-r--r-- | sys/src/cmd/vmx/nanosec.c | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/sys/src/cmd/vmx/nanosec.c b/sys/src/cmd/vmx/nanosec.c new file mode 100644 index 000000000..c11bc01ab --- /dev/null +++ b/sys/src/cmd/vmx/nanosec.c @@ -0,0 +1,50 @@ +#include <u.h> +#include <libc.h> + +/* + * nsec() is wallclock and can be adjusted by timesync + * so need to use cycles() instead, but fall back to + * nsec() in case we can't + * + * "fasthz" is how many ticks there are in a second + * can be read from /dev/time + */ +uvlong +nanosec(void) +{ + static uvlong fasthz, xstart; + uvlong x, div; + int f, n, i; + char tmp[128], *e; + + if(fasthz == ~0ULL) + return nsec() - xstart; + + if(fasthz == 0){ + fasthz = ~0ULL; + xstart = nsec(); + if((f = open("/dev/time", OREAD)) >= 0 && (n = read(f, tmp, sizeof(tmp)-1)) > 2){ + tmp[n] = 0; + e = tmp; + for(i = 0; i < 3; i++) + strtoll(e, &e, 10); + if((fasthz = strtoll(e, nil, 10)) < 1) + fasthz = ~0ULL; + else + cycles(&xstart); + } + close(f); + if(fasthz == ~0ULL){ + fprint(2, "couldn't get fasthz, falling back to nsec()\n"); + fprint(2, "you might want to disable aux/timesync\n"); + return 0; + } + } + cycles(&x); + x -= xstart; + + /* this is ugly */ + for(div = 1000000000ULL; x < 0x1999999999999999ULL && div > 1 ; div /= 10ULL, x *= 10ULL); + + return x / (fasthz / div); +} |