Add gtod_reduce option
authorJens Axboe <jens.axboe@oracle.com>
Fri, 14 Nov 2008 12:04:53 +0000 (13:04 +0100)
committerJens Axboe <jens.axboe@oracle.com>
Fri, 14 Nov 2008 12:04:53 +0000 (13:04 +0100)
This cuts down even more on gtod() calls. While the three disable_X
options halved the gettimeofday() call count, this can reduce it to
less than 1 percent of what it otherwise would have been.

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

diff --git a/HOWTO b/HOWTO
index 1d1aa61..f4efd28 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -848,6 +848,13 @@ disable_slat=bool Disable measurements of submission latency numbers. See
 disable_bw=bool        Disable measurements of throughput/bandwidth numbers. See
                disable_clat.
 
+gtod_reduce=bool Enable all of the gettimeofday() reducing options
+               (disable_clat, disable_slat, disable_bw) plus reduce
+               precision of the timeout somewhat to really shrink
+               the gettimeofday() call count. With this option enabled,
+               we only do about 0.4% of the gtod() calls we would have
+               done if all time keeping was enabled.
+
 
 6.0 Interpreting the output
 ---------------------------
diff --git a/fio.c b/fio.c
index 7fb9490..08011c9 100644 (file)
--- a/fio.c
+++ b/fio.c
@@ -156,6 +156,17 @@ static void set_sig_handlers(void)
        sigaction(SIGILL, &act, NULL);
 }
 
+static inline int should_check_rate(struct thread_data *td)
+{
+       /*
+        * No minimum rate set, always ok
+        */
+       if (!td->o.ratemin && !td->o.rate_iops_min)
+               return 0;
+
+       return 1;
+}
+
 /*
  * Check if we are above the minimum rate given.
  */
@@ -166,12 +177,6 @@ static int check_min_rate(struct thread_data *td, struct timeval *now)
        unsigned long spent;
        unsigned long rate;
 
-       /*
-        * No minimum rate set, always ok
-        */
-       if (!td->o.ratemin && !td->o.rate_iops_min)
-               return 0;
-
        /*
         * allow a 2 second settle period in the beginning
         */
@@ -340,6 +345,12 @@ requeue:
        return 0;
 }
 
+static inline void update_tv_cache(struct thread_data *td)
+{
+       if ((++td->tv_cache_nr & td->tv_cache_mask) == td->tv_cache_mask)
+               fio_gettime(&td->tv_cache, NULL);
+}
+
 /*
  * The main verify engine. Runs over the writes we previously submitted,
  * reads the blocks back in, and checks the crc/md5 of the data.
@@ -377,7 +388,9 @@ static void do_verify(struct thread_data *td)
                if (!io_u)
                        break;
 
-               if (runtime_exceeded(td, &io_u->start_time)) {
+               update_tv_cache(td);
+
+               if (runtime_exceeded(td, &td->tv_cache)) {
                        put_io_u(td, io_u);
                        td->terminate = 1;
                        break;
@@ -490,7 +503,6 @@ sync_done:
  */
 static void do_io(struct thread_data *td)
 {
-       struct timeval s;
        unsigned long usec;
        unsigned int i;
        int ret = 0;
@@ -514,9 +526,9 @@ static void do_io(struct thread_data *td)
                if (!io_u)
                        break;
 
-               memcpy(&s, &io_u->start_time, sizeof(s));
+               update_tv_cache(td);
 
-               if (runtime_exceeded(td, &s)) {
+               if (runtime_exceeded(td, &td->tv_cache)) {
                        put_io_u(td, io_u);
                        td->terminate = 1;
                        break;
@@ -564,7 +576,9 @@ static void do_io(struct thread_data *td)
                                requeue_io_u(td, &io_u);
                        } else {
 sync_done:
-                               fio_gettime(&comp_time, NULL);
+                               if (should_check_rate(td))
+                                       fio_gettime(&comp_time, NULL);
+
                                bytes_done = io_u_sync_complete(td, io_u);
                                if (bytes_done < 0)
                                        ret = bytes_done;
@@ -603,7 +617,8 @@ sync_done:
                        if (full && !min_evts)
                                min_evts = 1;
 
-                       fio_gettime(&comp_time, NULL);
+                       if (should_check_rate(td))
+                               fio_gettime(&comp_time, NULL);
 
                        do {
                                ret = io_u_queued_complete(td, min_evts);
@@ -624,8 +639,8 @@ sync_done:
                 * of completions except the very first one which may look
                 * a little bursty
                 */
-               if (!in_ramp_time(td)) {
-                       usec = utime_since(&s, &comp_time);
+               if (!in_ramp_time(td) && should_check_rate(td)) {
+                       usec = utime_since(&td->tv_cache, &comp_time);
 
                        rate_throttle(td, usec, bytes_done);
 
@@ -977,6 +992,7 @@ static void *thread_main(void *data)
        while (keep_running(td)) {
                fio_gettime(&td->start, NULL);
                memcpy(&td->ts.stat_sample_time, &td->start, sizeof(td->start));
+               memcpy(&td->tv_cache, &td->start, sizeof(td->start));
 
                if (td->o.ratemin)
                        memcpy(&td->lastrate, &td->ts.stat_sample_time,
diff --git a/fio.h b/fio.h
index ed1257c..3e39aea 100644 (file)
--- a/fio.h
+++ b/fio.h
@@ -499,6 +499,7 @@ struct thread_options {
        unsigned int disable_clat;
        unsigned int disable_slat;
        unsigned int disable_bw;
+       unsigned int gtod_reduce;
 
        char *read_iolog_file;
        char *write_iolog_file;
@@ -612,6 +613,9 @@ struct thread_data {
        struct timeval epoch;   /* time job was started */
        struct timeval rw_end[2];
        struct timeval last_issue;
+       struct timeval tv_cache;
+       unsigned int tv_cache_nr;
+       unsigned int tv_cache_mask;
        unsigned int rw_end_set[2];
        unsigned int ramp_time_over;
 
diff --git a/io_u.c b/io_u.c
index 62a76b9..8863fa7 100644 (file)
--- a/io_u.c
+++ b/io_u.c
@@ -851,7 +851,8 @@ struct io_u *get_io_u(struct thread_data *td)
 
 out:
        if (!td_io_prep(td, io_u)) {
-               fio_gettime(&io_u->start_time, NULL);
+               if (!td->o.disable_slat)
+                       fio_gettime(&io_u->start_time, NULL);
                return io_u;
        }
 err_put:
index d4fc184..f068ebd 100644 (file)
--- a/options.c
+++ b/options.c
@@ -432,6 +432,20 @@ static int str_lockfile_cb(void *data, const char *str)
        return 0;
 }
 
+static int str_gtod_reduce_cb(void *data, int *il)
+{
+       struct thread_data *td = data;
+       int val = *il;
+
+       td->o.disable_clat = !!val;
+       td->o.disable_slat = !!val;
+       td->o.disable_bw = !!val;
+       if (val)
+               td->tv_cache_mask = 63;
+
+       return 0;
+}
+
 #define __stringify_1(x)       #x
 #define __stringify(x)         __stringify_1(x)
 
@@ -1290,11 +1304,19 @@ static struct fio_option options[] = {
                .def    = "1",
        },
 #endif
+       {
+               .name   = "gtod_reduce",
+               .type   = FIO_OPT_BOOL,
+               .help   = "Greatly reduce number of gettimeofday() calls",
+               .cb     = str_gtod_reduce_cb,
+               .def    = "0",
+       },
        {
                .name   = "disable_clat",
                .type   = FIO_OPT_BOOL,
                .off1   = td_var_offset(disable_clat),
                .help   = "Disable completion latency numbers",
+               .parent = "gtod_reduce",
                .def    = "0",
        },
        {
@@ -1302,6 +1324,7 @@ static struct fio_option options[] = {
                .type   = FIO_OPT_BOOL,
                .off1   = td_var_offset(disable_slat),
                .help   = "Disable submissionn latency numbers",
+               .parent = "gtod_reduce",
                .def    = "0",
        },
        {
@@ -1309,6 +1332,7 @@ static struct fio_option options[] = {
                .type   = FIO_OPT_BOOL,
                .off1   = td_var_offset(disable_bw),
                .help   = "Disable bandwidth logging",
+               .parent = "gtod_reduce",
                .def    = "0",
        },
        {