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Store the clock offset table inside the trace

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The ovnisync tool now generates it by default inside ovni directory,
and the emulator recognizes it by default if exists.
This commit is contained in:
Rodrigo Arias 2022-09-19 17:36:10 +02:00
parent 834b33af33
commit 675c4f9ee8
4 changed files with 168 additions and 31 deletions
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34
doc/runtime/distributed.md Normal file
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@ -0,0 +1,34 @@
# Distributed traces (MPI)
The ovni trace is designed to support concurrent programs running in different
nodes in a cluster. It is often the case that the monotonic clock
(`CLOCK_MONOTONIC`) are not synchronized between machines (in general they
measure the time since boot).
To generate a coherent Paraver trace, the offsets of the clocks need to be
provided to the emulator too. To do so, run the `ovnisync` program using MPI on
the same nodes your workload will use. If you are using SLURM, you may want to
use something like:
% srun ./application
% srun ovnisync
!!! warning
Beware that you cannot launch two MPI programs inside the same srun session,
you must invoke srun twice.
By default, it will generate the `ovni/clock-offsets.txt` file, with the
relative offsets to the rank 0 of MPI. The emulator will automatically pick the
offsets when processing the trace. Use the ovnisync `-o` option to select a
different output path (see the `-c` option in ovniemu to load the file).
Here is an example table with three nodes, all units are in nanoseconds. The
standard deviation is less than 1 us:
```
rank hostname offset_median offset_mean offset_std
0 xeon01 0 0.000000 0.000000
1 xeon04 1165382584 1165382582.900000 135.286341
2 xeon05 3118113507 3118113599.070000 180.571610
```

23
emu.c
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@ -1,4 +1,4 @@
/* Copyright (c) 2021 Barcelona Supercomputing Center (BSC)
/* Copyright (c) 2021-2022 Barcelona Supercomputing Center (BSC)
* SPDX-License-Identifier: GPL-3.0-or-later */
#define _POSIX_C_SOURCE 200112L
@ -849,8 +849,11 @@ load_clock_offsets(struct ovni_emu *emu)
struct ovni_trace *trace;
struct ovni_stream *stream;
if(emu->clock_offset_file != NULL)
{
f = fopen(emu->clock_offset_file, "r");
/* If provided by the user, it must exist */
if(f == NULL)
{
err("error opening clock offset file %s: %s\n",
@ -858,6 +861,24 @@ load_clock_offsets(struct ovni_emu *emu)
strerror(errno));
exit(EXIT_FAILURE);
}
}
else
{
char path[PATH_MAX];
if(snprintf(path, PATH_MAX, "%s/clock-offsets.txt",
emu->tracedir) >= PATH_MAX)
{
die("clock offset path too long\n");
}
f = fopen(path, "r");
if(f == NULL)
{
/* May not exist, but is fine */
return;
}
}
/* Ignore header line */
if(fgets(buf, 1024, f) == NULL)

1
mkdocs.yml
View File

@ -22,6 +22,7 @@ nav:
- concepts.md
- 'Runtime':
- runtime/tracing.md
- runtime/distributed.md
- runtime/kernel.md
- runtime/trace_spec.md
- 'Emulation':

127
ovnisync.c
View File

@ -1,16 +1,19 @@
/* Copyright (c) 2021 Barcelona Supercomputing Center (BSC)
/* Copyright (c) 2021-2022 Barcelona Supercomputing Center (BSC)
* SPDX-License-Identifier: GPL-3.0-or-later */
#define _POSIX_C_SOURCE 200112L
#define _POSIX_C_SOURCE 200809L
#include <errno.h>
#include <limits.h>
#include <time.h>
#include <stdio.h>
#include <mpi.h>
#include <stdlib.h>
#include <math.h>
#include <unistd.h>
#include <mpi.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#include "ovni.h"
@ -50,6 +53,7 @@ struct options {
int ndrift_samples;
int drift_wait; /* in seconds */
int verbose;
char *outpath;
};
static double
@ -91,11 +95,59 @@ usage(void)
{
fprintf(stderr, "%s: clock synchronization utility\n", progname);
fprintf(stderr, "\n");
fprintf(stderr, "Usage: %s [-d ndrift_samples] [-v] [-n nsamples] [-w drift_delay]\n",
fprintf(stderr, "Usage: %s [-o outfile] [-d ndrift_samples] [-v] [-n nsamples] [-w drift_delay]\n",
progname);
exit(EXIT_FAILURE);
}
static int
try_mkdir(const char *path, mode_t mode)
{
struct stat st;
if(stat(path, &st) != 0)
{
/* Directory does not exist */
return mkdir(path, mode);
}
else if(!S_ISDIR(st.st_mode))
{
errno = ENOTDIR;
return -1;
}
return 0;
}
static int
mkpath(const char *path, mode_t mode)
{
char *pp;
char *sp;
int status;
char *copypath = strdup(path);
/* Remove trailing slash */
int last = strlen(path) - 1;
while (last > 0 && copypath[last] == '/')
copypath[last--] = '\0';
status = 0;
pp = copypath;
while (status == 0 && (sp = strchr(pp, '/')) != 0) {
if (sp != pp) {
/* Neither root nor double slash in path */
*sp = '\0';
status = try_mkdir(copypath, mode);
*sp = '/';
}
pp = sp + 1;
}
free(copypath);
return status;
}
static void
parse_options(struct options *options, int argc, char *argv[])
{
@ -106,8 +158,9 @@ parse_options(struct options *options, int argc, char *argv[])
options->nsamples = 100;
options->verbose = 0;
options->drift_wait = 5;
options->outpath = "ovni/clock-offsets.txt";
while ((opt = getopt(argc, argv, "d:vn:w:")) != -1) {
while ((opt = getopt(argc, argv, "d:vn:w:o:h")) != -1) {
switch (opt) {
case 'd':
options->ndrift_samples = atoi(optarg);
@ -121,6 +174,10 @@ parse_options(struct options *options, int argc, char *argv[])
case 'n':
options->nsamples = atoi(optarg);
break;
case 'o':
options->outpath = optarg;
break;
case 'h':
default: /* '?' */
usage();
}
@ -326,46 +383,48 @@ build_offset_table(int nsamples, int rank, int verbose)
}
static void
print_drift_header(struct offset_table *table)
print_drift_header(FILE *out, struct offset_table *table)
{
int i;
//char buf[64];
printf("%-20s", "wallclock");
fprintf(out, "%-20s", "wallclock");
for(i=0; i<table->nprocs; i++)
{
//sprintf(buf, "rank%d", i);
printf(" %-20s", table->offset[i]->hostname);
fprintf(out, " %-20s", table->offset[i]->hostname);
}
printf("\n");
fprintf(out, "\n");
}
static void
print_drift_row(struct offset_table *table)
print_drift_row(FILE *out, struct offset_table *table)
{
int i;
printf("%-20f", table->offset[0]->wall_t1);
fprintf(out, "%-20f", table->offset[0]->wall_t1);
for(i=0; i<table->nprocs; i++)
printf(" %-20ld", table->offset[i]->offset);
fprintf(out, " %-20ld", table->offset[i]->offset);
printf("\n");
fprintf(out, "\n");
}
static void
print_table_detailed(struct offset_table *table)
print_table_detailed(FILE *out, struct offset_table *table)
{
int i;
struct offset *offset;
printf("%-10s %-20s %-20s %-20s %-20s\n", "rank", "hostname", "offset_median", "offset_mean", "offset_std");
fprintf(out, "%-10s %-20s %-20s %-20s %-20s\n",
"rank", "hostname", "offset_median", "offset_mean", "offset_std");
for(i=0; i<table->nprocs; i++)
{
offset = table->offset[i];
printf("%-10d %-20s %-20ld %-20f %-20f\n",
fprintf(out, "%-10d %-20s %-20ld %-20f %-20f\n",
i, offset->hostname, offset->offset,
offset->delta_mean, offset->delta_std);
}
@ -377,9 +436,28 @@ do_work(struct options *options, int rank)
int drift_mode;
int i;
struct offset_table *table;
FILE *out = NULL;
drift_mode = options->ndrift_samples > 1 ? 1 : 0;
if(rank == 0)
{
if(mkpath(options->outpath, 0755) != 0)
{
fprintf(stderr, "mkpath(%s) failed: %s\n",
options->outpath, strerror(errno));
exit(EXIT_FAILURE);
}
out = fopen(options->outpath, "w");
if(out == NULL)
{
fprintf(stderr, "fopen(%s) failed: %s\n",
options->outpath, strerror(errno));
exit(EXIT_FAILURE);
}
}
for(i=0; i<options->ndrift_samples; i++)
{
table = build_offset_table(options->nsamples, rank, options->verbose);
@ -389,13 +467,13 @@ do_work(struct options *options, int rank)
if(drift_mode)
{
if(i == 0)
print_drift_header(table);
print_drift_header(out, table);
print_drift_row(table);
print_drift_row(out, table);
}
else
{
print_table_detailed(table);
print_table_detailed(out, table);
}
free(table->_offset);
@ -406,6 +484,9 @@ do_work(struct options *options, int rank)
if(drift_mode)
sleep(options->drift_wait);
}
if(rank == 0)
fclose(out);
}
int