Hi,
I'm wanting to use fio to test the latency of a storage system at various bandwidths. While I could use a script to run fio repeatedly at various rate= settings, that would give the storage device some "settle" time between tests, and I'd prefer to keep the test running constantly.
I've added this feature to my local copy, and it *just about* works ;) Config file and patch attached. Here's my problem: I'm getting a blip in bandwidth every time I step up the rate. This is very obvious when used with low rates/steps, like the config file below.
Second problem, at high rates/steps (like 1m/1m), bandwidth logging gets messed up. While tracking this down, it appeared that after the first rate step, td->bw_sample_time was getting reset every 250ms whereas the default bw_avg_time is 500ms, hence no logging. (Note: if I analyze the latency logs, it appears the stepping did actually work correctly, and with no spikes.)
As I keep messing with this, it's clear I don't fully understand the interaction between my change and the big loop in thread_main(). Can someone here take a look at my changes and give me some guidance?
Many thanks,
Josh
-- fio job file
[global]
thread
ioengine=null
size=1m
time_based
runtime=30s
write_bw_log
write_lat_log
[ratestep]
rw=write
rate=,10k
ratestep=,5k
bs=4k
- Adding "ratestep=" option to config files; when used with "rate="
option, it will step the rate up by ratestep every (ratecycle * 5)
milliseconds. (Yea, should make the step interval configurable
separately.)
- Added step_rate() near the end of do_io(), just after we do the
check_min_rate() part.
Currently very fiddly; seems to get blips in bandwidth just after a
rate step, also at high rates/steps it messes up bandwidth logging.
Need feedback from mailing list.
---
fio.c | 40 ++++++++++++++++++++++++++++++++++++++++
fio.h | 4 +++-
init.c | 4 ++++
options.c | 8 ++++++++
4 files changed, 55 insertions(+), 1 deletions(-)
diff --git a/fio.c b/fio.c
index 5b58ab8..9063c03 100644
--- a/fio.c
+++ b/fio.c
@@ -341,6 +341,39 @@ static int check_min_rate(struct thread_data *td, struct timeval *now,
return ret;
}
+static int __step_rate(struct thread_data *td, struct timeval *now,
+ enum fio_ddir ddir)
+{
+ unsigned long spent;
+ unsigned long long new_rate;
+
+ assert(ddir_rw(ddir));
+
+ if (!td->o.ratestep[ddir])
+ return 0;
+
+ spent = mtime_since(&td->lastratestep[ddir], now);
+
+ if (spent < td->o.ratecycle * 5)
+ return 0;
+
+ new_rate = td->rate_bps[ddir] + td->o.ratestep[ddir];
+ td->o.rate[ddir] = td->rate_bps[ddir] = new_rate;
+
+ memcpy(&td->lastratestep[ddir], now, sizeof(*now));
+ return 0;
+}
+
+static int step_rate(struct thread_data *td, struct timeval *now)
+{
+ int ret = 0;
+
+ ret |= __step_rate(td, now, DDIR_READ);
+ ret |= __step_rate(td, now, DDIR_WRITE);
+
+ return ret;
+}
+
static inline int runtime_exceeded(struct thread_data *td, struct timeval *t)
{
if (!td->o.timeout)
@@ -813,6 +846,8 @@ sync_done:
td_verror(td, EIO, "check_min_rate");
break;
}
+
+ step_rate(td, &comp_time);
}
if (td->o.thinktime) {
@@ -1237,6 +1272,11 @@ static void *thread_main(void *data)
fio_gettime(&td->epoch, NULL);
getrusage(RUSAGE_SELF, &td->ru_start);
+ if (td->o.ratestep[0] || td->o.ratestep[1]) {
+ memcpy(&td->lastratestep[0], &td->epoch, sizeof(td->epoch));
+ memcpy(&td->lastratestep[1], &td->epoch, sizeof(td->epoch));
+ }
+
clear_state = 0;
while (keep_running(td)) {
fio_gettime(&td->start, NULL);
diff --git a/fio.h b/fio.h
index cc1f65f..36b15aa 100644
--- a/fio.h
+++ b/fio.h
@@ -212,6 +212,7 @@ struct thread_options {
unsigned int rate[2];
unsigned int ratemin[2];
+ unsigned int ratestep[2];
unsigned int ratecycle;
unsigned int rate_iops[2];
unsigned int rate_iops_min[2];
@@ -361,6 +362,7 @@ struct thread_data {
unsigned long rate_bytes[2];
unsigned long rate_blocks[2];
struct timeval lastrate[2];
+ struct timeval lastratestep[2];
unsigned long long total_io_size;
unsigned long long fill_device_size;
@@ -659,7 +661,7 @@ static inline int __should_check_rate(struct thread_data *td,
* If some rate setting was given, we need to check it
*/
if (o->rate[ddir] || o->ratemin[ddir] || o->rate_iops[ddir] ||
- o->rate_iops_min[ddir])
+ o->rate_iops_min[ddir] || o->ratestep[ddir])
return 1;
return 0;
diff --git a/init.c b/init.c
index 482ce09..717dfc5 100644
--- a/init.c
+++ b/init.c
@@ -498,6 +498,10 @@ static int fixup_options(struct thread_data *td)
log_err("fio: minimum rate exceeds rate\n");
ret = 1;
}
+ if ((o->ratestep[0] && !o->rate[0]) || (o->ratestep[1] && !o->rate[1])) {
+ log_err("fio: ratestep requires initial rate also set\n");
+ ret = 1;
+ }
if (!o->timeout && o->time_based) {
log_err("fio: time_based requires a runtime/timeout setting\n");
diff --git a/options.c b/options.c
index 53c3a82..a276bcb 100644
--- a/options.c
+++ b/options.c
@@ -1772,6 +1772,14 @@ static struct fio_option options[FIO_MAX_OPTS] = {
.help = "Job must meet this rate or it will be shutdown",
.parent = "rate",
},
+ {
+ .name = "ratestep",
+ .type = FIO_OPT_INT,
+ .off1 = td_var_offset(ratestep[0]),
+ .off2 = td_var_offset(ratestep[1]),
+ .help = "Job will increment bandwidth rate by this amount each ratecycle",
+ .parent = "rate",
+ },
{
.name = "rate_iops",
.type = FIO_OPT_INT,
--
1.7.4.4
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