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Better overhead estimate.
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rosinski committed Jun 17, 2005
1 parent f9ec315 commit 94450c7
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Showing 2 changed files with 71 additions and 10 deletions.
40 changes: 30 additions & 10 deletions gptl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,7 @@ static long ticks_per_sec; /* clock ticks per second */

/* Local function prototypes */

static void printstats (const Timer *, FILE *, const int, const bool);
static void printstats (const Timer *, FILE *, const int, const bool, float);
static void add (Timer *, const Timer *);
static inline int get_cpustamp (long *, long *);
static inline Timer *getentry (const Hashentry *, const char *, int *);
Expand Down Expand Up @@ -573,6 +573,7 @@ int GPTLreset (void)

int GPTLpr (const int id) /* output file will be named "timing.<id>" */
{
struct timeval tp1, tp2; /* argument returned from gettimeofday */
FILE *fp; /* file handle to write to */
Timer *ptr; /* walk through master thread linked list */
Timer *tptr; /* walk through slave threads linked lists */
Expand All @@ -581,6 +582,7 @@ int GPTLpr (const int id) /* output file will be named "timing.<id>" */
char outfile[12]; /* name of output file: timing.xxxx */
float *sum; /* sum of overhead values (per thread) */
float osum; /* sum of overhead over threads */
float gtodoverhead; /* overhead of calling gettimeofday */
bool found; /* jump out of loop when name found */
bool foundany; /* whether summation print necessary */
bool first; /* flag 1st time entry found */
Expand All @@ -604,6 +606,15 @@ int GPTLpr (const int id) /* output file will be named "timing.<id>" */
fp = stderr;

sum = (float *) GPTLallocate (nthreads * sizeof (float));

/*
** Determine gettimeofday() overhead to further refine per-timer overhead estimate
*/

gettimeofday (&tp1, 0);
gettimeofday (&tp2, 0);
gtodoverhead = (tp2.tv_sec - tp1.tv_sec) +
1.e-6*(tp2.tv_usec - tp1.tv_usec);

for (t = 0; t < nthreads; ++t) {
if (t > 0)
Expand Down Expand Up @@ -634,14 +645,15 @@ int GPTLpr (const int id) /* output file will be named "timing.<id>" */
fprintf (fp, "\n"); /* Done with titles, go to next line */

for (ptr = timers[t]; ptr; ptr = ptr->next)
printstats (ptr, fp, t, true);
printstats (ptr, fp, t, true, gtodoverhead);

/* Sum of overhead across timers is meaningful */

if (wallstats.enabled && overheadstats.enabled) {
sum[t] = 0;
for (ptr = timers[t]; ptr; ptr = ptr->next)
sum[t] += ptr->wall.overhead;
for (ptr = timers[t]; ptr; ptr = ptr->next) {
sum[t] += ptr->wall.overhead + ptr->count * 2 * gtodoverhead;
}
fprintf (fp, "Overhead sum = %9.3f wallclock seconds\n", sum[t]);
}
}
Expand Down Expand Up @@ -691,21 +703,21 @@ int GPTLpr (const int id) /* output file will be named "timing.<id>" */
if (first) {
first = false;
fprintf (fp, "%3.3d ", 0);
printstats (ptr, fp, 0, false);
printstats (ptr, fp, 0, false, gtodoverhead);
}

found = true;
foundany = true;
fprintf (fp, "%3.3d ", t);
printstats (tptr, fp, 0, false);
printstats (tptr, fp, 0, false, gtodoverhead);
add (&sumstats, tptr);
}
}
}

if (foundany) {
fprintf (fp, "SUM ");
printstats (&sumstats, fp, 0, false);
printstats (&sumstats, fp, 0, false, gtodoverhead);
fprintf (fp, "\n");
}
}
Expand Down Expand Up @@ -766,7 +778,8 @@ int GPTLpr (const int id) /* output file will be named "timing.<id>" */
static void printstats (const Timer *timer, /* timer to print */
FILE *fp, /* file descriptor to write to */
const int t, /* thread number */
const bool doindent) /* whether indenting will be done */
const bool doindent, /* whether indenting will be done */
float gtodoverhead) /* gettimeofday overhead */
{
int i; /* index */
int indent; /* index for indenting */
Expand Down Expand Up @@ -812,8 +825,15 @@ static void printstats (const Timer *timer, /* timer to print */
if (wallstats.enabled) {
elapse = timer->wall.accum_sec + 1.e-6*timer->wall.accum_usec;
fprintf (fp, "%9.3f %9.3f %9.3f ", elapse, timer->wall.max, timer->wall.min);
if (overheadstats.enabled)
fprintf (fp, "%9.3f ", timer->wall.overhead);

/*
** Add cost of gettimeofday to overhead est. Factor of 2 is because both
** start and stop were called.
*/

if (overheadstats.enabled) {
fprintf (fp, "%9.3f ", timer->wall.overhead + timer->count * 2 * gtodoverhead);
}
}

#ifdef HAVE_PAPI
Expand Down
41 changes: 41 additions & 0 deletions tests/overhead.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h> /* gettimeofday */

#ifdef THREADED_OMP
#include <omp.h>
Expand Down Expand Up @@ -135,6 +136,46 @@ static void overhead (int iter, int ninvoke)
GPTLstart ("2or4PAPI_reads");
GPTLstop ("2or4PAPI_reads");
}

struct timeval tp1, tp2; /* argument returned from gettimeofday */
float overhead;

gettimeofday (&tp1, 0);
for (i = 0; i < ninvoke/10; ++i) {
GPTLstart ("overhead_est.");
GPTLstop ("overhead_est.");
GPTLstart ("overhead_est.");
GPTLstop ("overhead_est.");
GPTLstart ("overhead_est.");
GPTLstop ("overhead_est.");
GPTLstart ("overhead_est.");
GPTLstop ("overhead_est.");
GPTLstart ("overhead_est.");
GPTLstop ("overhead_est.");
GPTLstart ("overhead_est.");
GPTLstop ("overhead_est.");
GPTLstart ("overhead_est.");
GPTLstop ("overhead_est.");
GPTLstart ("overhead_est.");
GPTLstop ("overhead_est.");
GPTLstart ("overhead_est.");
GPTLstop ("overhead_est.");
GPTLstart ("overhead_est.");
GPTLstop ("overhead_est.");
}
gettimeofday (&tp2, 0);
overhead = (tp2.tv_sec - tp1.tv_sec) +
1.e-6*(tp2.tv_usec - tp1.tv_usec);
printf ("overhead = %f sec. Compare to 'overhead_est' in timing output\n", overhead);
/*
for (i = 0; i < ninvoke/10; ++i) {
gettimeofday (&tp1, 0);
gettimeofday (&tp2, 0);
overhead = (tp2.tv_sec - tp1.tv_sec) +
1.e-6*(tp2.tv_usec - tp1.tv_usec);
printf ("tp2.tv_usec diff=%d\n", tp2.tv_usec - tp1.tv_usec);
}
*/
}

static void *getentry (char *string,
Expand Down

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