lbvmon: expose clock_gettime(CLOCK_BOOTTIME)

Exposed as VMON_SYS_STAT_BOOTTIME, so part of VMON_WANT_SYS_STAT,
in units of ticks to normalize with SYS_STAT_CPU* times.

This also introduces vmon->ticks_per_sec, which callers can access
as well for convenience since vmon_t is all public and this library
doesn't aspire to keep anything private.  It's initialized via
sysconf(_SC_CLK_TCK) @ vmon_init().

3 files changed, 26 insertions, 3 deletions

diff --git a/src/libvmon/defs/sys_stat.def b/src/libvmon/defs/sys_stat.def
index ef8b9a7..9d252f6 100644
--- a/src/libvmon/defs/sys_stat.def
+++ b/src/libvmon/defs/sys_stat.def
@@ -1,6 +1,10 @@
 #include "_begin.def"
 
 		/* 		member name,	symbolic constant,	human label,	human description (think UI/help) */
+
+	/* clock_gettime(CLOCK_BOOTTIME) */
+vmon_datum_ulonglong(		boottime,	SYS_STAT_BOOTTIME,	"BootTime",	"Time since boot (ticks)")
+
 	/* /proc/stat */
 
 /* a cpu row, this is shown once for the total prefixed with "cpu  ", then again for every cpu prefixed with "cpuN ", newlines terminate rows */
diff --git a/src/libvmon/vmon.c b/src/libvmon/vmon.c
index 78ad905..83d78c4 100644
--- a/src/libvmon/vmon.c
+++ b/src/libvmon/vmon.c
@@ -28,6 +28,7 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <string.h>
+#include <time.h>
 #include <inttypes.h>
 #include <dirent.h>
 #include <errno.h>
@@ -864,9 +865,11 @@ typedef enum _vmon_sys_stat_fsm_t {
 /* system-wide stat sampling, things like CPU usages, stuff in /proc/stat */
 static sample_ret_t sys_sample_stat(vmon_t *vmon, vmon_sys_stat_t **store)
 {
-	int			i, len, total = 0;
-	int			changes = 0;
-	vmon_sys_stat_fsm_t	state = VMON_PARSER_STATE_SYS_STAT_CPU_PREFIX;	/* this could be defined as the "VMON_PARSER_INITIAL_STATE" */
+	int				i, len, total = 0;
+	int				changes = 0;
+	vmon_sys_stat_fsm_t		state = VMON_PARSER_STATE_SYS_STAT_CPU_PREFIX;	/* this could be defined as the "VMON_PARSER_INITIAL_STATE" */
+	struct timespec			ts;
+	typeof((*store)->boottime)	boottime;
 #define VMON_PREPARE_PARSER
 #include "defs/sys_stat.def"
 
@@ -880,6 +883,20 @@ static sample_ret_t sys_sample_stat(vmon_t *vmon, vmon_sys_stat_t **store)
 		(*store)->stat_fd = openat(dirfd(vmon->proc_dir), "stat", O_RDONLY);
 	}
 
+#ifndef NSEC_PER_SEC
+#define NSEC_PER_SEC	1000000000
+#endif
+
+	/* VMON_SYS_STAT_BOOTTIME */
+	clock_gettime(CLOCK_BOOTTIME, &ts);
+	boottime = ts.tv_sec * vmon->ticks_per_sec;
+	boottime += ts.tv_nsec * vmon->ticks_per_sec / NSEC_PER_SEC;
+	if ((*store)->boottime != boottime) {
+		(*store)->boottime = boottime;
+		BITSET((*store)->changed, VMON_SYS_STAT_BOOTTIME);
+		changes++;
+	}
+
 	while ((len = try_pread((*store)->stat_fd, vmon->buf, sizeof(vmon->buf), total)) > 0) {
 		total += len;
 
@@ -983,6 +1000,7 @@ int vmon_init(vmon_t *vmon, vmon_flags_t flags, vmon_sys_wants_t sys_wants, vmon
 	vmon->flags = flags;
 	vmon->sys_wants = sys_wants;
 	vmon->proc_wants = proc_wants;
+	vmon->ticks_per_sec = sysconf(_SC_CLK_TCK);
 
 	/* here we populate the sys and proc function tables */
 #define vmon_want(_sym, _name, _func) \
diff --git a/src/libvmon/vmon.h b/src/libvmon/vmon.h
index 56c7b56..cefcb43 100644
--- a/src/libvmon/vmon.h
+++ b/src/libvmon/vmon.h
@@ -276,6 +276,7 @@ typedef struct _vmon_t {
 	vmon_flags_t		flags;				/* instance flags */
 	vmon_sys_wants_t	sys_wants;			/* system-wide wants mask */
 	vmon_proc_wants_t	proc_wants;			/* inherited per-process wants mask */
+	long			ticks_per_sec;			/* sysconf(_SC_CLK_TCK) */
 
 								/* function tables for mapping of wants bits to functions (sys-wide and per-process) */
 	int			(*sys_funcs[VMON_STORE_SYS_NR])(struct _vmon_t *, void **);