blktrace: add option to iterate over a trace multiple times

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@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/HOWTO b/HOWTO
index f94264b33c54437710fb4bf0994bc601912cb0b8..45cf0bdf4b7367a870f472d23aac8e45de60e43c 100644 (file)
--- 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 14acc6991cd0343157605c2fd1875a2b4c57aeee..1d33c6a43f6002b4f5c0de892398a6f9b8e54351 100644 (file)
--- 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 cebd54d6a58969b463f03219d8129d2fc88db6fc..72d74cf8ad30e72b00ca5c893bc7245ed8d9b835 100644 (file)
--- 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 dd136a086c61fd9dd97bea131ddc775c7082e4dc..50e45c63a636bf0be66299a8f20a0a9e75d264ae 100644 (file)
--- 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 620b6b3730f2432d00d7eec03675e23a533f2c85..81164ae03d26d677f3a0a1ab2f1abe5cea38b175 100644 (file)
--- 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 706f98fda4472455c8b49f0277d32f696110b22d..9b277309d26ac9eb83bbc23195c4dd95460ba418 100644 (file)
--- 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 3d5e0115954fd40f09b374ba615427845dc7674e..40b9eac2de9852a27449b79b3946d952ee64127d 100644 (file)
--- 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 f77574949d5f45c5d28880871cde5067d1922915..4f791cf366dd38360cb31a53daa32a4ca2cae4e1 100644 (file)
--- 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;