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Fixed the pacing logic in bootchart data collection.

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Ideally bootchart collects system data every BOOTCHART_POLLING_MS ms.
However, the current bootchart pacing logic would collect data every
time the main loop in init.c is executed. This results in:

1. Multiple data samples being taken consecutively or prematurely. In
many cases, these data samples have the same timestamp (in jiffies).
The off-line data processing tool would complain about dividing by
zero "interval" and bail out.

2. Because of the ineffective pacing, bootchart data collection would
terminate prematurely. The total duration of data collection is usually
much shorter than what the user specifies.

The fix is to check whether BOOTCHART_POLLING_MS ms has elapsed
before taking a new data sample. For this purpose, /proc/uptime
is used to get the time values, consistent with the precision of
bootchart timestamps.

Change-Id: I106bf91dbda01059b719df6c73b8bd1cd54a64f0
Signed-off-by: Bo (Andover) Zhang <zhang@broadcom.com>
This commit is contained in:
Bo (Andover) Zhang 2014-07-24 13:11:35 -04:00
parent 73290cd136
commit 3700373c67
3 changed files with 47 additions and 20 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

37
init/bootchart.c
View file

@ -119,6 +119,18 @@ file_buff_done( FileBuff buff )
}
}
static long long
get_uptime_jiffies()
{
char buff[64];
long long jiffies = 0;
if (proc_read("/proc/uptime", buff, sizeof(buff)) > 0)
jiffies = 100LL*strtod(buff,NULL);
return jiffies;
}
static void
log_header(void)
{
@ -185,22 +197,11 @@ static void
do_log_uptime(FileBuff log)
{
char buff[65];
int fd, ret, len;
int len;
fd = open("/proc/uptime",O_RDONLY);
if (fd >= 0) {
int ret;
ret = unix_read(fd, buff, 64);
close(fd);
buff[64] = 0;
if (ret >= 0) {
long long jiffies = 100LL*strtod(buff,NULL);
int len;
snprintf(buff,sizeof(buff),"%lld\n",jiffies);
len = strlen(buff);
file_buff_write(log, buff, len);
}
}
snprintf(buff,sizeof(buff),"%lld\n",get_uptime_jiffies());
len = strlen(buff);
file_buff_write(log, buff, len);
}
static void
@ -376,3 +377,9 @@ void bootchart_finish( void )
file_buff_done(log_procs);
acct(NULL);
}
/* called to get time (in ms) used by bootchart */
long long bootchart_gettime( void )
{
return 10LL*get_uptime_jiffies();
}

1
init/bootchart.h
View file

@ -26,6 +26,7 @@
extern int bootchart_init(void);
extern int bootchart_step(void);
extern void bootchart_finish(void);
extern long long bootchart_gettime(void);
# define BOOTCHART_POLLING_MS 200 /* polling period in ms */
# define BOOTCHART_DEFAULT_TIME_SEC (2*60) /* default polling time in seconds */

29
init/init.c
View file

@ -65,6 +65,7 @@ static int property_triggers_enabled = 0;
#if BOOTCHART
static int bootchart_count;
static long long bootchart_time = 0;
#endif
static char console[32];
@ -1147,11 +1148,29 @@ int main(int argc, char **argv)
#if BOOTCHART
if (bootchart_count > 0) {
if (timeout < 0 || timeout > BOOTCHART_POLLING_MS)
timeout = BOOTCHART_POLLING_MS;
if (bootchart_step() < 0 || --bootchart_count == 0) {
bootchart_finish();
bootchart_count = 0;
long long current_time;
int elapsed_time, remaining_time;
current_time = bootchart_gettime();
elapsed_time = current_time - bootchart_time;
if (elapsed_time >= BOOTCHART_POLLING_MS) {
/* count missed samples */
while (elapsed_time >= BOOTCHART_POLLING_MS) {
elapsed_time -= BOOTCHART_POLLING_MS;
bootchart_count--;
}
/* count may be negative, take a sample anyway */
bootchart_time = current_time;
if (bootchart_step() < 0 || bootchart_count <= 0) {
bootchart_finish();
bootchart_count = 0;
}
}
if (bootchart_count > 0) {
remaining_time = BOOTCHART_POLLING_MS - elapsed_time;
if (timeout < 0 || timeout > remaining_time)
timeout = remaining_time;
}
}
#endif