diff options
author | Baptiste Jonglez <git@bitsofnetworks.org> | 2016-09-05 22:02:40 +0200 |
---|---|---|
committer | Baptiste Jonglez <git@bitsofnetworks.org> | 2016-11-12 19:29:39 +0100 |
commit | a3d894000b7243e4bfd54f99de3bee8154827897 (patch) | |
tree | cb8870c2922315e1491763303ed084337ecc2020 /src | |
parent | 8b2638c349f780a0a66f6b4ef2430747d97bf24b (diff) |
Use a monotonic clock instead of a realtime clock
Using a realtime clock is a bad idea: it is affected by any kind of time
change, which can happen when the administrator modifies the system time,
or more simply when a laptop suspends to RAM and then wakes up from sleep.
With the current approach of using a realtime clock:
- if the system time jumps forward (e.g. when resuming after a
suspend-to-RAM), bmon would take 100% CPU and display random graph data
extremely fast, until it "catches up" with the new time.
- if the system time jumps backwards, bmon would freeze until *time*
"catches up" to the point it was before. bmon then (incorrectly)
displays a spike in the graph, because lots of packets have been
sent/received since the last update.
Instead of using gettimeofday(), switch to clock_gettime() with
CLOCK_MONOTONIC on systems that support it. OS X does not provide
clock_gettime(), so this commit also adds a Mach-specific implementation.
This change has been tested on Linux 4.1 with glibc and musl, and on
FreeBSD 10.0-RELEASE-p12.
Diffstat (limited to 'src')
-rw-r--r-- | src/utils.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/src/utils.c b/src/utils.c index 248d829..7db96e7 100644 --- a/src/utils.c +++ b/src/utils.c @@ -27,6 +27,11 @@ #include <bmon/conf.h> #include <bmon/utils.h> +#ifdef __MACH__ +#include <mach/clock.h> +#include <mach/mach.h> +#endif + void *xcalloc(size_t n, size_t s) { void *d = calloc(n, s); @@ -112,12 +117,21 @@ int timestamp_is_negative(timestamp_t *ts) void update_timestamp(timestamp_t *dst) { - struct timeval tv; +#ifdef __MACH__ + clock_serv_t cclock; + mach_timespec_t tp; - gettimeofday(&tv, NULL); + host_get_clock_service(mach_host_self(), SYSTEM_CLOCK, &cclock); + clock_get_time(cclock, &tp); + mach_port_deallocate(mach_task_self(), cclock); +#else + struct timespec tp; + + clock_gettime(CLOCK_MONOTONIC, &tp); +#endif - dst->tv_sec = tv.tv_sec; - dst->tv_usec = tv.tv_usec; + dst->tv_sec = tp.tv_sec; + dst->tv_usec = tp.tv_nsec / 1000; } void copy_timestamp(timestamp_t *ts1, timestamp_t *ts2) |