diff options
| -rw-r--r-- | src/charts.c | 54 |
1 files changed, 44 insertions, 10 deletions
diff --git a/src/charts.c b/src/charts.c index fd66932..ae01c75 100644 --- a/src/charts.c +++ b/src/charts.c @@ -40,12 +40,13 @@ #include "vwm.h" #endif -#define CHART_ISTHREAD_ARGV "~" /* use this string to mark threads in the argv field */ -#define CHART_NOCOMM_ARGV "# missed it!" /* use this string to substitute the command when missing in argv field */ -#define CHART_MAX_ARGC 64 /* this is a huge amount */ -#define CHART_VMON_PROC_WANTS (VMON_WANT_PROC_STAT | VMON_WANT_PROC_FOLLOW_CHILDREN | VMON_WANT_PROC_FOLLOW_THREADS) -#define CHART_VMON_SYS_WANTS (VMON_WANT_SYS_STAT) -#define CHART_MAX_COLUMNS 16 +#define CHART_ISTHREAD_ARGV "~" /* use this string to mark threads in the argv field */ +#define CHART_NOCOMM_ARGV "# missed it!" /* use this string to substitute the command when missing in argv field */ +#define CHART_MAX_ARGC 64 /* this is a huge amount */ +#define CHART_VMON_PROC_WANTS (VMON_WANT_PROC_STAT | VMON_WANT_PROC_FOLLOW_CHILDREN | VMON_WANT_PROC_FOLLOW_THREADS) +#define CHART_VMON_SYS_WANTS (VMON_WANT_SYS_STAT) +#define CHART_MAX_COLUMNS 16 +#define CHART_DELTA_SECONDS_EPSILON .001f /* adherence errors smaller than this are treated as zero */ /* the global charts state, supplied to vwm_chart_create() which keeps a reference for future use. */ typedef struct _vwm_charts_t { @@ -1296,16 +1297,29 @@ static float delta(struct timeval *cur, struct timeval *prev) } +static inline int delta_close_enough(vwm_charts_t *charts, float delta) +{ + float remainder = charts->sampling_interval_secs - delta; + + /* if within .1ms of the scheduled next sample (or behind schedule at all), consider it "close enough" and take the sample. */ + if (remainder <= CHART_DELTA_SECONDS_EPSILON) + return 1; + + return 0; +} + + /* update the charts if necessary, return if updating occurred, and duration before another update needed in *desired_delay_us */ int vwm_charts_update(vwm_charts_t *charts, int *desired_delay_us) { + int ret = 0, sampled = 0; float this_delta = 0.0f; - int ret = 0; gettimeofday(&charts->maybe_sample, NULL); + this_delta = delta(&charts->maybe_sample, &charts->this_sample); if (!charts->primed || (charts->sampling_interval_secs == INFINITY && !charts->sampling_paused) || /* XXX this is kind of a kludge to get the 0 Hz indicator drawn before pausing */ - (charts->sampling_interval_secs != INFINITY && ((this_delta = delta(&charts->maybe_sample, &charts->this_sample)) >= charts->sampling_interval_secs))) { + (charts->sampling_interval_secs != INFINITY && delta_close_enough(charts, this_delta))) { vmon_sys_stat_t *sys_stat; /* automatically lower the sample rate if we can't keep up with the current sample rate */ @@ -1359,10 +1373,30 @@ int vwm_charts_update(vwm_charts_t *charts, int *desired_delay_us) /* "primed" is just a flag to ensure we always perform the first sample */ if (!charts->primed) charts->primed = 1; + + sampled = 1; } - /* TODO: make some effort to compute how long to sleep, but this is perfectly fine for now. */ - *desired_delay_us = charts->sampling_interval_secs == INFINITY ? -1 : charts->sampling_interval_secs * 300000.0; + if (charts->sampling_interval_secs == INFINITY) { + *desired_delay_us = -1; /* sleep forever */ + } else { + float remaining_secs; + + if (sampled) { /* sampling takes time, so let's subtract that from the interval-derived sleep time to try get the next sample started on-time (if possible) */ + struct timeval post_sampled; + + gettimeofday(&post_sampled, NULL); + this_delta += delta(&post_sampled, &charts->this_sample); + } + + remaining_secs = charts->sampling_interval_secs - this_delta; + if (remaining_secs <= 0) { + /* always sleep some minimal amount, we don't want to spin */ + *desired_delay_us = CHART_DELTA_SECONDS_EPSILON * 1000000.f; + } else { + *desired_delay_us = remaining_secs * 1000000.f; + } + } return ret; } |