Fix rate option with iodepth > 1
authorRadha Ramachandran <radha@google.com>
Wed, 9 Dec 2009 21:31:44 +0000 (22:31 +0100)
committerJens Axboe <jens.axboe@oracle.com>
Wed, 9 Dec 2009 21:31:44 +0000 (22:31 +0100)
The rate option currently doesnt work when used with libaio engine.
The math currently, calculates the time t2 (when the I/O completed) -
t1 (when the io_u unit was created) as the time it takes for the I/O
and the bandwidth for the rate calculation is calculated from that.
This math will work correctly for sync engine as there is only one io
in progress at a time, but for libaio engine, when there are multiple
I/Os queued, the same time (as in from t1 to t2) could be attributed
to other I/Os as well so the actual bandwidth is actually higher.
I have a patch, but this is more brute force where I take the total
bytes read/written divided by the time since I/Os started to calculate
the bandwidth and decide on the time that needs to be spent sleeping
(if any).This is a little more heavy weight than the previous math. I
think there are probably simpler/cleaner solutions than this but this
is the current patch I have for it.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
fio.h
gettime.c
init.c
io_u.c

diff --git a/fio.h b/fio.h
index 3b2dd6e..119dc09 100644 (file)
--- a/fio.h
+++ b/fio.h
@@ -359,7 +359,7 @@ struct thread_data {
        /*
         * Rate state
         */
-       unsigned long rate_usec_cycle[2];
+       unsigned long rate_nsec_cycle[2];
        long rate_pending_usleep[2];
        unsigned long rate_bytes[2];
        unsigned long rate_blocks[2];
index c0d27e4..8ec70b9 100644 (file)
--- a/gettime.c
+++ b/gettime.c
@@ -10,7 +10,7 @@
 
 #include "hash.h"
 
-static int clock_gettime_works;
+static int clock_gettime_works = 0;
 static struct timeval last_tv;
 static int last_tv_valid;
 
diff --git a/init.c b/init.c
index 6ae78be..b9dee19 100644 (file)
--- a/init.c
+++ b/init.c
@@ -205,21 +205,19 @@ static void put_job(struct thread_data *td)
 static int __setup_rate(struct thread_data *td, enum fio_ddir ddir)
 {
        unsigned int bs = td->o.min_bs[ddir];
-       unsigned long long rate;
-       unsigned long ios_per_msec;
+       unsigned long long bytes_per_sec;
 
-       if (td->o.rate[ddir]) {
-               rate = td->o.rate[ddir];
-               ios_per_msec = (rate * 1000LL) / bs;
-       } else
-               ios_per_msec = td->o.rate_iops[ddir] * 1000UL;
+       if (td->o.rate[ddir])
+               bytes_per_sec = td->o.rate[ddir];
+       else
+               bytes_per_sec = td->o.rate_iops[ddir] * bs;
 
-       if (!ios_per_msec) {
+       if (!bytes_per_sec) {
                log_err("rate lower than supported\n");
                return -1;
        }
 
-       td->rate_usec_cycle[ddir] = 1000000000ULL / ios_per_msec;
+       td->rate_nsec_cycle[ddir] = 1000000000ULL / bytes_per_sec;
        td->rate_pending_usleep[ddir] = 0;
        return 0;
 }
diff --git a/io_u.c b/io_u.c
index 4be958d..1845d3b 100644 (file)
--- a/io_u.c
+++ b/io_u.c
@@ -984,6 +984,7 @@ static void io_completed(struct thread_data *td, struct io_u *io_u,
        if (!io_u->error) {
                unsigned int bytes = io_u->buflen - io_u->resid;
                const enum fio_ddir idx = io_u->ddir;
+               const enum fio_ddir odx = io_u->ddir ^ 1;
                int ret;
 
                td->io_blocks[idx]++;
@@ -992,15 +993,10 @@ static void io_completed(struct thread_data *td, struct io_u *io_u,
 
                if (ramp_time_over(td)) {
                        unsigned long uninitialized_var(lusec);
-                       unsigned long uninitialized_var(rusec);
 
                        if (!td->o.disable_clat || !td->o.disable_bw)
                                lusec = utime_since(&io_u->issue_time,
                                                        &icd->time);
-                       if (__should_check_rate(td, idx) ||
-                           __should_check_rate(td, idx ^ 1))
-                               rusec = utime_since(&io_u->start_time,
-                                                       &icd->time);
 
                        if (!td->o.disable_clat) {
                                add_clat_sample(td, idx, lusec, bytes);
@@ -1009,11 +1005,16 @@ static void io_completed(struct thread_data *td, struct io_u *io_u,
                        if (!td->o.disable_bw)
                                add_bw_sample(td, idx, bytes, &icd->time);
                        if (__should_check_rate(td, idx)) {
-                               td->rate_pending_usleep[idx] +=
-                                       (long) td->rate_usec_cycle[idx] - rusec;
+                               td->rate_pending_usleep[idx] =
+                                       ((td->this_io_bytes[idx] *
+                                         td->rate_nsec_cycle[idx]) / 1000 -
+                                        utime_since_now(&td->start));
                        }
                        if (__should_check_rate(td, idx ^ 1))
-                               td->rate_pending_usleep[idx ^ 1] -= rusec;
+                               td->rate_pending_usleep[odx] =
+                                       ((td->this_io_bytes[odx] *
+                                         td->rate_nsec_cycle[odx]) / 1000 -
+                                        utime_since_now(&td->start));
                }
 
                if (td_write(td) && idx == DDIR_WRITE &&