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Add --latency-limit option to pgbench.

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This allows transactions that take longer than specified limit to be counted
separately. With --rate, transactions that are already late by the time we
get to execute them are skipped altogether. Using --latency-limit with
--rate allows you to "catch up" more quickly, if there's a hickup in the
server causing a lot of transactions to stall momentarily.

Fabien COELHO, reviewed by Rukh Meski and heavily refactored by me.
pull/14/head
Heikki Linnakangas 11 years ago
parent 30d7ae3c76
commit 98aed6c721
2 changed files with 235 additions and 66 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 177
      contrib/pgbench/pgbench.c
  2. 70
      doc/src/sgml/pgbench.sgml

177
contrib/pgbench/pgbench.c
Unescape View File

@ -140,6 +140,14 @@ double sample_rate = 0.0;
*/
int64 throttle_delay = 0;
/*
* Transactions which take longer than this limit (in usec) are counted as
* late, and reported as such, although they are completed anyway. When
* throttling is enabled, execution time slots that are more than this late
* are skipped altogether, and counted separately.
*/
int64 latency_limit = 0;
/*
* tablespace selection
*/
@ -238,6 +246,8 @@ typedef struct
int64 throttle_trigger; /* previous/next throttling (us) */
int64 throttle_lag; /* total transaction lag behind throttling */
int64 throttle_lag_max; /* max transaction lag */
int64 throttle_latency_skipped; /* lagging transactions skipped */
int64 latency_late; /* late transactions */
} TState;
#define INVALID_THREAD ((pthread_t) 0)
@ -250,6 +260,8 @@ typedef struct
int64 sqlats;
int64 throttle_lag;
int64 throttle_lag_max;
int64 throttle_latency_skipped;
int64 latency_late;
} TResult;
/*
@ -284,6 +296,8 @@ typedef struct
long start_time; /* when does the interval start */
int cnt; /* number of transactions */
int skipped; /* number of transactions skipped under
* --rate and --latency-limit */
double min_latency; /* min/max latencies */
double max_latency;
@ -348,7 +362,7 @@ static void setalarm(int seconds);
static void *threadRun(void *arg);
static void doLog(TState *thread, CState *st, FILE *logfile, instr_time *now,
AggVals *agg);
AggVals *agg, bool skipped);
static void
usage(void)
@ -375,6 +389,8 @@ usage(void)
" -f, --file=FILENAME read transaction script from FILENAME\n"
" -j, --jobs=NUM number of threads (default: 1)\n"
" -l, --log write transaction times to log file\n"
" -L, --latency-limit=NUM count transactions lasting more than NUM ms\n"
" as late.\n"
" -M, --protocol=simple|extended|prepared\n"
" protocol for submitting queries (default: simple)\n"
" -n, --no-vacuum do not run VACUUM before tests\n"
@ -994,7 +1010,9 @@ void
agg_vals_init(AggVals *aggs, instr_time start)
{
/* basic counters */
aggs->cnt = 0; /* number of transactions */
aggs->cnt = 0; /* number of transactions (includes skipped) */
aggs->skipped = 0; /* xacts skipped under --rate --latency-limit */
aggs->sum_latency = 0; /* SUM(latency) */
aggs->sum2_latency = 0; /* SUM(latency*latency) */
@ -1050,8 +1068,34 @@ top:
int64 wait = getPoissonRand(thread, throttle_delay);
thread->throttle_trigger += wait;
st->txn_scheduled = thread->throttle_trigger;
/*
* If this --latency-limit is used, and this slot is already late so
* that the transaction will miss the latency limit even if it
* completed immediately, we skip this time slot and iterate till the
* next slot that isn't late yet.
*/
if (latency_limit)
{
int64 now_us;
if (INSTR_TIME_IS_ZERO(now))
INSTR_TIME_SET_CURRENT(now);
now_us = INSTR_TIME_GET_MICROSEC(now);
while (thread->throttle_trigger < now_us - latency_limit)
{
thread->throttle_latency_skipped++;
if (logfile)
doLog(thread, st, logfile, &now, agg, true);
wait = getPoissonRand(thread, throttle_delay);
thread->throttle_trigger += wait;
st->txn_scheduled = thread->throttle_trigger;
}
}
st->sleeping = 1;
st->throttling = true;
st->is_throttled = true;
@ -1119,12 +1163,13 @@ top:
if (commands[st->state + 1] == NULL)
{
/* only calculate latency if an option is used that needs it */
if (progress || throttle_delay)
if (progress || throttle_delay || latency_limit)
{
int64 latency;
if (INSTR_TIME_IS_ZERO(now))
INSTR_TIME_SET_CURRENT(now);
latency = INSTR_TIME_GET_MICROSEC(now) - st->txn_scheduled;
st->txn_latencies += latency;
@ -1137,11 +1182,15 @@ top:
* transactions, overflow would take 256 hours.
*/
st->txn_sqlats += latency * latency;
/* record over the limit transactions if needed. */
if (latency_limit && latency > latency_limit)
thread->latency_late++;
}
/* record the time it took in the log */
if (logfile)
doLog(thread, st, logfile, &now, agg);
doLog(thread, st, logfile, &now, agg, false);
}
if (commands[st->state]->type == SQL_COMMAND)
@ -1227,7 +1276,7 @@ top:
}
/* Record transaction start time under logging, progress or throttling */
if ((logfile || progress || throttle_delay) && st->state == 0)
if ((logfile || progress || throttle_delay || latency_limit) && st->state == 0)
{
INSTR_TIME_SET_CURRENT(st->txn_begin);
@ -1605,7 +1654,8 @@ top:
* print log entry after completing one transaction.
*/
static void
doLog(TState *thread, CState *st, FILE *logfile, instr_time *now, AggVals *agg)
doLog(TState *thread, CState *st, FILE *logfile, instr_time *now, AggVals *agg,
bool skipped)
{
double lag;
double latency;
@ -1622,6 +1672,9 @@ doLog(TState *thread, CState *st, FILE *logfile, instr_time *now, AggVals *agg)
INSTR_TIME_SET_CURRENT(*now);
latency = (double) (INSTR_TIME_GET_MICROSEC(*now) - st->txn_scheduled);
if (skipped)
lag = latency;
else
lag = (double) (INSTR_TIME_GET_MICROSEC(st->txn_begin) - st->txn_scheduled);
/* should we aggregate the results or not? */
@ -1634,6 +1687,13 @@ doLog(TState *thread, CState *st, FILE *logfile, instr_time *now, AggVals *agg)
if (agg->start_time + agg_interval >= INSTR_TIME_GET_DOUBLE(*now))
{
agg->cnt += 1;
if (skipped)
{
/* there is no latency to record if the transaction was skipped */
agg->skipped += 1;
}
else
{
agg->sum_latency += latency;
agg->sum2_latency += latency * latency;
@ -1656,6 +1716,7 @@ doLog(TState *thread, CState *st, FILE *logfile, instr_time *now, AggVals *agg)
agg->max_lag = lag;
}
}
}
else
{
/*
@ -1677,11 +1738,15 @@ doLog(TState *thread, CState *st, FILE *logfile, instr_time *now, AggVals *agg)
agg->min_latency,
agg->max_latency);
if (throttle_delay)
{
fprintf(logfile, " %.0f %.0f %.0f %.0f",
agg->sum_lag,
agg->sum2_lag,
agg->min_lag,
agg->max_lag);
if (latency_limit)
fprintf(logfile, " %d", agg->skipped);
}
fputc('\n', logfile);
/* move to the next inteval */
@ -1689,6 +1754,7 @@ doLog(TState *thread, CState *st, FILE *logfile, instr_time *now, AggVals *agg)
/* reset for "no transaction" intervals */
agg->cnt = 0;
agg->skipped = 0;
agg->min_latency = 0;
agg->max_latency = 0;
agg->sum_latency = 0;
@ -1701,10 +1767,11 @@ doLog(TState *thread, CState *st, FILE *logfile, instr_time *now, AggVals *agg)
/* reset the values to include only the current transaction. */
agg->cnt = 1;
agg->skipped = skipped ? 1 : 0;
agg->min_latency = latency;
agg->max_latency = latency;
agg->sum_latency = latency;
agg->sum2_latency = latency * latency;
agg->sum_latency = skipped ? 0.0 : latency;
agg->sum2_latency = skipped ? 0.0 : latency * latency;
agg->min_lag = lag;
agg->max_lag = lag;
agg->sum_lag = lag;
@ -1717,12 +1784,21 @@ doLog(TState *thread, CState *st, FILE *logfile, instr_time *now, AggVals *agg)
#ifndef WIN32
/* This is more than we really ought to know about instr_time */
if (skipped)
fprintf(logfile, "%d %d skipped %d %ld %ld",
st->id, st->cnt, st->use_file,
(long) now->tv_sec, (long) now->tv_usec);
else
fprintf(logfile, "%d %d %.0f %d %ld %ld",
st->id, st->cnt, latency, st->use_file,
(long) now->tv_sec, (long) now->tv_usec);
#else
/* On Windows, instr_time doesn't provide a timestamp anyway */
if (skipped)
fprintf(logfile, "%d %d skipped %d 0 0",
st->id, st->cnt, st->use_file);
else
fprintf(logfile, "%d %d %.0f %d 0 0",
st->id, st->cnt, latency, st->use_file);
#endif
@ -2424,7 +2500,8 @@ printResults(int ttype, int64 normal_xacts, int nclients,
TState *threads, int nthreads,
instr_time total_time, instr_time conn_total_time,
int64 total_latencies, int64 total_sqlats,
int64 throttle_lag, int64 throttle_lag_max)
int64 throttle_lag, int64 throttle_lag_max,
int64 throttle_latency_skipped, int64 latency_late)
{
double time_include,
tps_include,
@ -2463,7 +2540,17 @@ printResults(int ttype, int64 normal_xacts, int nclients,
normal_xacts);
}
if (throttle_delay || progress)
if (throttle_delay && latency_limit)
printf("number of transactions skipped: " INT64_FORMAT " (%.3f %%)\n",
throttle_latency_skipped,
100.0 * throttle_latency_skipped / (throttle_latency_skipped + normal_xacts));
if (latency_limit)
printf("number of transactions above the %.1f ms latency limit: " INT64_FORMAT " (%.3f %%)\n",
latency_limit / 1000.0, latency_late,
100.0 * latency_late / (throttle_latency_skipped + normal_xacts));
if (throttle_delay || progress || latency_limit)
{
/* compute and show latency average and standard deviation */
double latency = 0.001 * total_latencies / normal_xacts;
@ -2578,6 +2665,7 @@ main(int argc, char **argv)
{"sampling-rate", required_argument, NULL, 4},
{"aggregate-interval", required_argument, NULL, 5},
{"rate", required_argument, NULL, 'R'},
{"latency-limit", required_argument, NULL, 'L'},
{NULL, 0, NULL, 0}
};
@ -2607,6 +2695,8 @@ main(int argc, char **argv)
int64 total_sqlats = 0;
int64 throttle_lag = 0;
int64 throttle_lag_max = 0;
int64 throttle_latency_skipped = 0;
int64 latency_late = 0;
int i;
@ -2651,7 +2741,7 @@ main(int argc, char **argv)
state = (CState *) pg_malloc(sizeof(CState));
memset(state, 0, sizeof(CState));
while ((c = getopt_long(argc, argv, "ih:nvp:dqSNc:j:Crs:t:T:U:lf:D:F:M:P:R:", long_options, &optindex)) != -1)
while ((c = getopt_long(argc, argv, "ih:nvp:dqSNc:j:Crs:t:T:U:lf:D:F:M:P:R:L:", long_options, &optindex)) != -1)
{
switch (c)
{
@ -2848,6 +2938,18 @@ main(int argc, char **argv)
throttle_delay = (int64) (1000000.0 / throttle_value);
}
break;
case 'L':
{
double limit_ms = atof(optarg);
if (limit_ms <= 0.0)
{
fprintf(stderr, "invalid latency limit: %s\n", optarg);
exit(1);
}
benchmarking_option_set = true;
latency_limit = (int64) (limit_ms * 1000);
}
break;
case 0:
/* This covers long options which take no argument. */
if (foreign_keys || unlogged_tables)
@ -3143,6 +3245,8 @@ main(int argc, char **argv)
thread->random_state[0] = random();
thread->random_state[1] = random();
thread->random_state[2] = random();
thread->throttle_latency_skipped = 0;
thread->latency_late = 0;
if (is_latencies)
{
@ -3217,6 +3321,8 @@ main(int argc, char **argv)
total_latencies += r->latencies;
total_sqlats += r->sqlats;
throttle_lag += r->throttle_lag;
throttle_latency_skipped += r->throttle_latency_skipped;
latency_late += r->latency_late;
if (r->throttle_lag_max > throttle_lag_max)
throttle_lag_max = r->throttle_lag_max;
INSTR_TIME_ADD(conn_total_time, r->conn_time);
@ -3239,7 +3345,8 @@ main(int argc, char **argv)
INSTR_TIME_SUBTRACT(total_time, start_time);
printResults(ttype, total_xacts, nclients, threads, nthreads,
total_time, conn_total_time, total_latencies, total_sqlats,
throttle_lag, throttle_lag_max);
throttle_lag, throttle_lag_max, throttle_latency_skipped,
latency_late);
return 0;
}
@ -3264,7 +3371,8 @@ threadRun(void *arg)
int64 last_count = 0,
last_lats = 0,
last_sqlats = 0,
last_lags = 0;
last_lags = 0,
last_skipped = 0;
AggVals aggs;
@ -3467,7 +3575,8 @@ threadRun(void *arg)
/* generate and show report */
int64 count = 0,
lats = 0,
sqlats = 0;
sqlats = 0,
skipped = 0;
int64 lags = thread->throttle_lag;
int64 run = now - last_report;
double tps,
@ -3490,23 +3599,26 @@ threadRun(void *arg)
sqlat = 1.0 * (sqlats - last_sqlats) / (count - last_count);
stdev = 0.001 * sqrt(sqlat - 1000000.0 * latency * latency);
lag = 0.001 * (lags - last_lags) / (count - last_count);
skipped = thread->throttle_latency_skipped - last_skipped;
if (throttle_delay)
fprintf(stderr,
"progress %d: %.1f s, %.1f tps, "
"lat %.3f ms stddev %.3f, lag %.3f ms\n",
thread->tid, total_run, tps, latency, stdev, lag);
else
fprintf(stderr,
"progress %d: %.1f s, %.1f tps, "
"lat %.3f ms stddev %.3f\n",
"lat %.3f ms stddev %.3f",
thread->tid, total_run, tps, latency, stdev);
if (throttle_delay)
{
fprintf(stderr, ", lag %.3f ms", lag);
if (latency_limit)
fprintf(stderr, ", skipped " INT64_FORMAT, skipped);
}
fprintf(stderr, "\n");
last_count = count;
last_lats = lats;
last_sqlats = sqlats;
last_lags = lags;
last_report = now;
last_skipped = thread->throttle_latency_skipped;
next_report += (int64) progress *1000000;
}
}
@ -3525,7 +3637,8 @@ threadRun(void *arg)
int64 count = 0,
lats = 0,
sqlats = 0,
lags = 0;
lags = 0,
skipped = 0;
int64 run = now - last_report;
double tps,
total_run,
@ -3550,23 +3663,26 @@ threadRun(void *arg)
sqlat = 1.0 * (sqlats - last_sqlats) / (count - last_count);
stdev = 0.001 * sqrt(sqlat - 1000000.0 * latency * latency);
lag = 0.001 * (lags - last_lags) / (count - last_count);
skipped = thread->throttle_latency_skipped - last_skipped;
if (throttle_delay)
fprintf(stderr,
"progress: %.1f s, %.1f tps, "
"lat %.3f ms stddev %.3f, lag %.3f ms\n",
total_run, tps, latency, stdev, lag);
else
fprintf(stderr,
"progress: %.1f s, %.1f tps, "
"lat %.3f ms stddev %.3f\n",
"lat %.3f ms stddev %.3f",
total_run, tps, latency, stdev);
if (throttle_delay)
{
fprintf(stderr, ", lag %.3f ms", lag);
if (latency_limit)
fprintf(stderr, ", " INT64_FORMAT " skipped", skipped);
}
fprintf(stderr, "\n");
last_count = count;
last_lats = lats;
last_sqlats = sqlats;
last_lags = lags;
last_report = now;
last_skipped = thread->throttle_latency_skipped;
next_report += (int64) progress *1000000;
}
}
@ -3587,6 +3703,9 @@ done:
}
result->throttle_lag = thread->throttle_lag;
result->throttle_lag_max = thread->throttle_lag_max;
result->throttle_latency_skipped = thread->throttle_latency_skipped;
result->latency_late = thread->latency_late;
INSTR_TIME_SET_CURRENT(end);
INSTR_TIME_ACCUM_DIFF(result->conn_time, end, start);
if (logfile)

70
doc/src/sgml/pgbench.sgml
Unescape View File

@ -344,6 +344,24 @@ pgbench <optional> <replaceable>options</> </optional> <replaceable>dbname</>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-L</option> <replaceable>limit</></term>
<term><option>--latency-limit=</option><replaceable>limit</></term>
<listitem>
<para>
Transaction which last more than <replaceable>limit</> milliseconds
are counted and reported separately, as <firstterm>late</>.
</para>
<para>
When throttling is used (<option>--rate=...</>), transactions that
lag behind schedule by more than <replaceable>limit</> ms, and thus
have no hope of meeting the latency limit, are not sent to the server
at all. They are counted and reported separately as
<firstterm>skipped</>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-M</option> <replaceable>querymode</></term>
<term><option>--protocol=</option><replaceable>querymode</></term>
@ -453,6 +471,15 @@ pgbench <optional> <replaceable>options</> </optional> <replaceable>dbname</>
latency.
</para>
<para>
If <option>--latency-limit</> is used together with <option>--rate</>,
a transaction can lag behind so much that it is already over the
latency limit when the previous transaction ends, because the latency
is calculated from the scheduled start time. Such transactions are
not sent to the server, but are skipped altogether and counted
separately.
</para>
<para>
A high schedule lag time is an indication that the system cannot
process transactions at the specified rate, with the chosen number of
@ -940,7 +967,7 @@ END;
The format of the log is:
<synopsis>
<replaceable>client_id</> <replaceable>transaction_no</> <replaceable>time</> <replaceable>file_no</> <replaceable>time_epoch</> <replaceable>time_us</> [<replaceable>schedule_lag</replaceable>]
<replaceable>client_id</> <replaceable>transaction_no</> <replaceable>time</> <replaceable>file_no</> <replaceable>time_epoch</> <replaceable>time_us</> <optional><replaceable>schedule_lag</replaceable></optional>
</synopsis>
where <replaceable>time</> is the total elapsed transaction time in microseconds,
@ -950,20 +977,40 @@ END;
UNIX epoch format timestamp and an offset
in microseconds (suitable for creating an ISO 8601
timestamp with fractional seconds) showing when
the transaction completed. The last field, <replaceable>schedule_lag</>, is
the difference between the transaction's scheduled start time, and the
time it actually started, in microseconds. It is only present when the
<option>--rate</> option is used.
the transaction completed.
Field <replaceable>schedule_lag</> is the difference between the
transaction's scheduled start time, and the time it actually started, in
microseconds. It is only present when the <option>--rate</> option is used.
The last field <replaceable>skipped_transactions</> reports the number of
transactions skipped because they were too far behind schedule. It is only
present when both options <option>--rate</> and <option>--latency-limit</>
are used.
</para>
<para>
Here are example outputs:
Here is a snippet of the log file generated:
<screen>
0 199 2241 0 1175850568 995598
0 200 2465 0 1175850568 998079
0 201 2513 0 1175850569 608
0 202 2038 0 1175850569 2663
</screen></para>
</screen>
Another example with --rate=100 and --latency-limit=5 (note the additional
<replaceable>schedule_lag</> column):
<screen>
0 81 4621 0 1412881037 912698 3005
0 82 6173 0 1412881037 914578 4304
0 83 skipped 0 1412881037 914578 5217
0 83 skipped 0 1412881037 914578 5099
0 83 4722 0 1412881037 916203 3108
0 84 4142 0 1412881037 918023 2333
0 85 2465 0 1412881037 919759 740
</screen>
In this example, transaction 82 was late, because it's latency (6.173 ms) was
over the 5 ms limit. The next two transactions were skipped, because they
were already late before they were even started.
</para>
<para>
When running a long test on hardware that can handle a lot of transactions,
@ -979,7 +1026,7 @@ END;
With the <option>--aggregate-interval</option> option, the logs use a bit different format:
<synopsis>
<replaceable>interval_start</> <replaceable>num_of_transactions</> <replaceable>latency_sum</> <replaceable>latency_2_sum</> <replaceable>min_latency</> <replaceable>max_latency</> [<replaceable>lag_sum</> <replaceable>lag_2_sum</> <replaceable>min_lag</> <replaceable>max_lag</>]
<replaceable>interval_start</> <replaceable>num_of_transactions</> <replaceable>latency_sum</> <replaceable>latency_2_sum</> <replaceable>min_latency</> <replaceable>max_latency</> <optional><replaceable>lag_sum</> <replaceable>lag_2_sum</> <replaceable>min_lag</> <replaceable>max_lag</> <optional><replaceable>skipped_transactions</></optional></optional>
</synopsis>
where <replaceable>interval_start</> is the start of the interval (UNIX epoch
@ -990,8 +1037,11 @@ END;
<replaceable>latency_2_sum</> is a sum of 2nd powers of latencies. The last two
fields are <replaceable>min_latency</> - a minimum latency within the interval, and
<replaceable>max_latency</> - maximum latency within the interval. A transaction is
counted into the interval when it was committed. The last four fields,
<replaceable>lag_sum</>, <replaceable>lag_2_sum</>, <replaceable>min_lag</>, and <replaceable>max_lag</>, are only present if the --rate option is used.
counted into the interval when it was committed. The fields in the end,
<replaceable>lag_sum</>, <replaceable>lag_2_sum</>, <replaceable>min_lag</>,
and <replaceable>max_lag</>, are only present if the <option>--rate</>
option is used. The very last one, <replaceable>skipped_transactions</>,
is only present if the option <option>--latency-limit</> is present, too.
They are calculated from the time each transaction had to wait for the
previous one to finish, i.e. the difference between each transaction's
scheduled start time and the time it actually started.

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