Scaling a particular trace may result in different runtimes among the
merging traces. By knowing the approximate length of each trace as a
user, the overall runtime of each can be tuned to line up by letting
certain traces loop multiple times.
First, the last timestamp of a trace is recorded at the end of the first
iteration to denote the length of a trace. This value is then used to
offset subsequent iterations of a trace.
Next, the "--merge_blktrace_iters" option is introduced to let the user
specify the number of times to loop over each specific trace. This is
done by passing a comma separated list that index-wise pairs with the
passed files in "--read_iolog". Iteration counts are introduced as well
as keeping track of the length of each trace.
In an example, given two traces, A and B, each 60s long. If we want to
see the impact of trace A issuing IOs twice as fast, the
--merge_blktrace_scalars="50:100" can be set and then
--merge_blktrace_iters="2:1". This runs trace A at 2x the speed twice for
approximately the same runtime as a single run of trace B.
Signed-off-by: Dennis Zhou <dennis@xxxxxxxxxx>
---
HOWTO | 21 +++++++++++++++++++++
blktrace.c | 23 +++++++++++++++++++++--
blktrace.h | 5 +++++
cconv.c | 6 ++++++
fio.1 | 22 ++++++++++++++++++++++
options.c | 10 ++++++++++
server.h | 2 +-
thread_options.h | 2 ++
8 files changed, 88 insertions(+), 3 deletions(-)
diff --git a/HOWTO b/HOWTO
index f94264b3..45cf0bdf 100644
--- a/HOWTO
+++ b/HOWTO
@@ -2514,6 +2514,14 @@ I/O replay
:option:`replay_time_scale` which scales the trace during runtime and
does not change the output of the merge unlike this option.
+.. option:: merge_blktrace_iters=float_list
+
+ This is a whole number option that is index paired with the list of files
+ passed to :option:`read_iolog`. When merging is performed, run each trace
+ for the specified number of iterations. For example,
+ ``--merge_blktrace_iters="2:1"`` runs the first trace for two iterations
+ and the second trace for one iteration.
+
.. option:: replay_no_stall=bool
When replaying I/O with :option:`read_iolog` the default behavior is to
@@ -3888,6 +3896,19 @@ being slowed down or sped up. :option:`merge_blktrace_scalars` takes in a colon
separated list of percentage scalars. It is index paired with the files passed
to :option:`read_iolog`.
+With scaling, it may be desirable to match the running time of all traces.
+This can be done with :option:`merge_blktrace_iters`. It is index paired with
+:option:`read_iolog` just like :option:`merge_blktrace_scalars`.
+
+In an example, given two traces, A and B, each 60s long. If we want to see
+the impact of trace A issuing IOs twice as fast and repeat trace A over the
+runtime of trace B, the following can be done::
+
+ $ fio --read_iolog="<trace_a>:"<trace_b>" --merge_blktrace_file"<output_file>" --merge_blktrace_scalars="50:100" --merge_blktrace_iters="2:1"
+
+This runs trace A at 2x the speed twice for approximately the same runtime as
+a single run of trace B.
+
CPU idleness profiling
----------------------
diff --git a/blktrace.c b/blktrace.c
index 14acc699..1d33c6a4 100644
--- a/blktrace.c
+++ b/blktrace.c
@@ -654,6 +654,12 @@ static int find_earliest_io(struct blktrace_cursor *bcs, int nr_logs)
static void merge_finish_file(struct blktrace_cursor *bcs, int i, int *nr_logs)
{
+ bcs[i].iter++;
+ if (bcs[i].iter < bcs[i].nr_iter) {
+ lseek(bcs[i].fd, 0, SEEK_SET);
+ return;
+ }
+
*nr_logs -= 1;
/* close file */
@@ -672,7 +678,11 @@ static int read_trace(struct thread_data *td, struct blktrace_cursor *bc)
read_skip:
/* read an io trace */
ret = trace_fifo_get(td, bc->fifo, bc->fd, t, sizeof(*t));
- if (ret <= 0) {
+ if (ret < 0) {
+ return ret;
+ } else if (!ret) {
+ if (!bc->length)
+ bc->length = bc->t.time;
return ret;
} else if (ret < (int) sizeof(*t)) {
log_err("fio: short fifo get\n");
@@ -697,7 +707,7 @@ read_skip:
goto read_skip;
}
- t->time = t->time * bc->scalar / 100;
+ t->time = (t->time + bc->iter * bc->length) * bc->scalar / 100;
return ret;
}
@@ -728,6 +738,15 @@ int merge_blktrace_iologs(struct thread_data *td)
goto err_param;
}
+ ret = init_merge_param_list(td->o.merge_blktrace_iters, bcs, nr_logs,
+ 1, offsetof(struct blktrace_cursor,
+ nr_iter));
+ if (ret) {
+ log_err("fio: merge_blktrace_iters(%d) != nr_logs(%d)\n",
+ ret, nr_logs);
+ goto err_param;
+ }
+
/* setup output file */
merge_fp = fopen(td->o.merge_blktrace_file, "w");
merge_buf = malloc(128 * 1024);
diff --git a/blktrace.h b/blktrace.h
index cebd54d6..72d74cf8 100644
--- a/blktrace.h
+++ b/blktrace.h
@@ -4,14 +4,19 @@
#ifdef FIO_HAVE_BLKTRACE
+#include <asm/types.h>
+
#include "blktrace_api.h"
struct blktrace_cursor {
struct fifo *fifo; // fifo queue for reading
int fd; // blktrace file
+ __u64 length; // length of trace
struct blk_io_trace t; // current io trace
int swap; // bitwise reverse required
int scalar; // scale percentage
+ int iter; // current iteration
+ int nr_iter; // number of iterations to run
};
bool is_blktrace(const char *, int *);
diff --git a/cconv.c b/cconv.c
index dd136a08..50e45c63 100644
--- a/cconv.c
+++ b/cconv.c
@@ -309,6 +309,9 @@ void convert_thread_options_to_cpu(struct thread_options *o,
for (i = 0; i < FIO_IO_U_LIST_MAX_LEN; i++)
o->merge_blktrace_scalars[i].u.f = fio_uint64_to_double(le64_to_cpu(top->merge_blktrace_scalars[i].u.i));
+
+ for (i = 0; i < FIO_IO_U_LIST_MAX_LEN; i++)
+ o->merge_blktrace_iters[i].u.f = fio_uint64_to_double(le64_to_cpu(top->merge_blktrace_iters[i].u.i));
#if 0
uint8_t cpumask[FIO_TOP_STR_MAX];
uint8_t verify_cpumask[FIO_TOP_STR_MAX];
@@ -574,6 +577,9 @@ void convert_thread_options_to_net(struct thread_options_pack *top,
for (i = 0; i < FIO_IO_U_LIST_MAX_LEN; i++)
top->merge_blktrace_scalars[i].u.i = __cpu_to_le64(fio_double_to_uint64(o->merge_blktrace_scalars[i].u.f));
+
+ for (i = 0; i < FIO_IO_U_LIST_MAX_LEN; i++)
+ top->merge_blktrace_iters[i].u.i = __cpu_to_le64(fio_double_to_uint64(o->merge_blktrace_iters[i].u.f));
#if 0
uint8_t cpumask[FIO_TOP_STR_MAX];
uint8_t verify_cpumask[FIO_TOP_STR_MAX];
diff --git a/fio.1 b/fio.1
index 620b6b37..81164ae0 100644
--- a/fio.1
+++ b/fio.1
@@ -2218,6 +2218,13 @@ second trace in realtime. This knob is separately tunable from
\fBreplay_time_scale\fR which scales the trace during runtime and will not
change the output of the merge unlike this option.
.TP
+.BI merge_blktrace_iters \fR=\fPfloat_list
+This is a whole number option that is index paired with the list of files
+passed to \fBread_iolog\fR. When merging is performed, run each trace for
+the specified number of iterations. For example,
+`\-\-merge_blktrace_iters="2:1"' runs the first trace for two iterations
+and the second trace for one iteration.
+.TP
.BI replay_no_stall \fR=\fPbool
When replaying I/O with \fBread_iolog\fR the default behavior is to
attempt to respect the timestamps within the log and replay them with the
@@ -3575,6 +3582,21 @@ Scaling traces can be done to see the relative impact of any particular trace
being slowed down or sped up. \fBmerge_blktrace_scalars\fR takes in a colon
separated list of percentage scalars. It is index paired with the files passed
to \fBread_iolog\fR.
+.P
+With scaling, it may be desirable to match the running time of all traces.
+This can be done with \fBmerge_blktrace_iters\fR. It is index paired with
+\fBread_iolog\fR just like \fBmerge_blktrace_scalars\fR.
+.P
+In an example, given two traces, A and B, each 60s long. If we want to see
+the impact of trace A issuing IOs twice as fast and repeat trace A over the
+runtime of trace B, the following can be done:
+.RS
+.P
+$ fio \-\-read_iolog="<trace_a>:"<trace_b>" \-\-merge_blktrace_file"<output_file>" \-\-merge_blktrace_scalars="50:100" \-\-merge_blktrace_iters="2:1"
+.RE
+.P
+This runs trace A at 2x the speed twice for approximately the same runtime as
+a single run of trace B.
.SH CPU IDLENESS PROFILING
In some cases, we want to understand CPU overhead in a test. For example, we
test patches for the specific goodness of whether they reduce CPU usage.
diff --git a/options.c b/options.c
index 706f98fd..9b277309 100644
--- a/options.c
+++ b/options.c
@@ -3217,6 +3217,16 @@ struct fio_option fio_options[FIO_MAX_OPTS] = {
.category = FIO_OPT_C_IO,
.group = FIO_OPT_G_IOLOG,
},
+ {
+ .name = "merge_blktrace_iters",
+ .lname = "Number of iterations to run per trace",
+ .type = FIO_OPT_FLOAT_LIST,
+ .off1 = offsetof(struct thread_options, merge_blktrace_iters),
+ .maxlen = FIO_IO_U_LIST_MAX_LEN,
+ .help = "Number of iterations to run per trace",
+ .category = FIO_OPT_C_IO,
+ .group = FIO_OPT_G_IOLOG,
+ },
{
.name = "exec_prerun",
.lname = "Pre-execute runnable",
diff --git a/server.h b/server.h
index 3d5e0115..40b9eac2 100644
--- a/server.h
+++ b/server.h
@@ -48,7 +48,7 @@ struct fio_net_cmd_reply {
};
enum {
- FIO_SERVER_VER = 76,
+ FIO_SERVER_VER = 77,
FIO_SERVER_MAX_FRAGMENT_PDU = 1024,
FIO_SERVER_MAX_CMD_MB = 2048,
diff --git a/thread_options.h b/thread_options.h
index f7757494..4f791cf3 100644
--- a/thread_options.h
+++ b/thread_options.h
@@ -260,6 +260,7 @@ struct thread_options {
char *write_iolog_file;
char *merge_blktrace_file;
fio_fp64_t merge_blktrace_scalars[FIO_IO_U_LIST_MAX_LEN];
+ fio_fp64_t merge_blktrace_iters[FIO_IO_U_LIST_MAX_LEN];
unsigned int write_bw_log;
unsigned int write_lat_log;
@@ -544,6 +545,7 @@ struct thread_options_pack {
uint8_t write_iolog_file[FIO_TOP_STR_MAX];
uint8_t merge_blktrace_file[FIO_TOP_STR_MAX];
fio_fp64_t merge_blktrace_scalars[FIO_IO_U_LIST_MAX_LEN];
+ fio_fp64_t merge_blktrace_iters[FIO_IO_U_LIST_MAX_LEN];
uint32_t write_bw_log;
uint32_t write_lat_log;
--
2.17.1
