gettime: offset CPU cycle counter by initial value

[fio.git] / gettime.c

diff --git a/gettime.c b/gettime.c
index e2746711d2e4e2b51b914a98a2c9d30e914beeda..a95b5452e5d5b3dcb382fb40ad7f79715ebfdc73 100644 (file)
--- a/gettime.c
+++ b/gettime.c
@@ -16,6 +16,8 @@
 #if defined(ARCH_HAVE_CPU_CLOCK) && !defined(ARCH_CPU_CLOCK_CYCLES_PER_USEC)
 static unsigned long cycles_per_usec;
 static unsigned long inv_cycles_per_usec;
+static uint64_t max_cycles_for_mult;
+static unsigned long long cycles_start, cycles_wrap;
 #endif
 int tsc_reliable = 0;
 
@@ -64,7 +66,7 @@ static struct gtod_log *find_hash(void *caller)
        return NULL;
 }
 
-static struct gtod_log *find_log(void *caller)
+static void inc_caller(void *caller)
 {
        struct gtod_log *log = find_hash(caller);
 
@@ -80,16 +82,13 @@ static struct gtod_log *find_log(void *caller)
                flist_add_tail(&log->list, &hash[h]);
        }
 
-       return log;
+       log->calls++;
 }
 
 static void gtod_log_caller(void *caller)
 {
-       if (gtod_inited) {
-               struct gtod_log *log = find_log(caller);
-
-               log->calls++;
-       }
+       if (gtod_inited)
+               inc_caller(caller);
 }
 
 static void fio_exit fio_dump_gtod(void)
@@ -171,18 +170,25 @@ static void __fio_gettime(struct timeval *tp)
                uint64_t usecs, t;
 
                t = get_cpu_clock();
-               if (t < tv->last_cycles && tv->last_tv_valid &&
-                   !tv->warned) {
-                       log_err("fio: CPU clock going back in time\n");
-                       tv->warned = 1;
+               if (t < cycles_start && !cycles_wrap)
+                       cycles_wrap = 1;
+               else if (cycles_wrap && t >= cycles_start) {
+                       if (!tv->warned) {
+                               log_err("fio: double CPU clock wrap\n");
+                               tv->warned = 1;
+                       }
                }
 
+               t -= cycles_start;
                tv->last_cycles = t;
                tv->last_tv_valid = 1;
 #ifdef ARCH_CPU_CLOCK_CYCLES_PER_USEC
                usecs = t / ARCH_CPU_CLOCK_CYCLES_PER_USEC;
 #else
-               usecs = (t * inv_cycles_per_usec) / 16777216UL;
+               if (t < max_cycles_for_mult)
+                       usecs = (t * inv_cycles_per_usec) / 16777216UL;
+               else
+                       usecs = t / cycles_per_usec;
 #endif
                tp->tv_sec = usecs / 1000000;
                tp->tv_usec = usecs % 1000000;
@@ -296,7 +302,10 @@ static int calibrate_cpu_clock(void)
 
        cycles_per_usec = avg;
        inv_cycles_per_usec = 16777216UL / cycles_per_usec;
+       max_cycles_for_mult = ~0ULL / inv_cycles_per_usec;
        dprint(FD_TIME, "inv_cycles_per_usec=%lu\n", inv_cycles_per_usec);
+       cycles_start = get_cpu_clock();
+       dprint(FD_TIME, "cycles_start=%llu\n", cycles_start);
        return 0;
 }
 #else