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Commit 3700373c authored by Bo (Andover) Zhang's avatar Bo (Andover) Zhang
Browse files

Fixed the pacing logic in bootchart data collection. 



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: default avatarBo (Andover) Zhang <zhang@broadcom.com>
parent 73290cd1

init/bootchart.c

+22 −15
Original line number Diff line number Diff line
@@ -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)

{
@@ -185,23 +197,12 @@ static void 
do_log_uptime(FileBuff  log)

{

    char  buff[65];

    int   fd, ret, 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);



    snprintf(buff,sizeof(buff),"%lld\n",get_uptime_jiffies());

    len = strlen(buff);

    file_buff_write(log, buff, len);

}

    }

}



static void

do_log_ln(FileBuff  log)
@@ -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();

}

init/bootchart.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */

init/init.c

+24 −5
Original line number Diff line number Diff line
@@ -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];
@@ -1147,13 +1148,31 @@ 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) {

            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



        nr = poll(ufds, fd_count, timeout);