blktrace: add option to scale a trace

As we explore stacking traces, it is nice to be able to scale a trace to
understand how the traces end up interacting.

This patch adds scaling by letting the user pass in percentages to scale
a trace by. When passed '--merge_blktrace_scalars="100"', the trace is
ran at 100% speed. If passed 50%, this will halve the trace timestamps.
The new option takes in a comma separated list that index-wise pairs
with the passed files in "--read_iolog".

This option differs from "--replay_time_scale" which scales the trace
during runtime and will not change the output unlike this option.

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

diff --git a/HOWTO b/HOWTO
index 0c767dd701c28a16917fcbfd591d22b9e579049b..f94264b33c54437710fb4bf0994bc601912cb0b8 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -2504,6 +2504,16 @@ I/O replay
        This limits the influence of the scheduler compared to replaying multiple
        blktraces via concurrent jobs.
 
+.. option:: merge_blktrace_scalars=float_list
+
+       This is a percentage based option that is index paired with the list of
+       files passed to :option:`read_iolog`. When merging is performed, scale
+       the time of each event by the corresponding amount. For example,
+       ``--merge_blktrace_scalars="50:100"`` runs the first trace in halftime
+       and the second trace in realtime. This knob is separately tunable from
+       :option:`replay_time_scale` which scales the trace during runtime and
+       does not change the output of the merge unlike this option.
+
 .. option:: replay_no_stall=bool
 
        When replaying I/O with :option:`read_iolog` the default behavior is to
@@ -3873,6 +3883,11 @@ only file passed to :option:`read_iolog`. An example would look like::
 Creating only the merged file can be done by passing the command line argument
 :option:`merge-blktrace-only`.
 
+Scaling traces can be done to see the relative impact of any particular trace
+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`.
+
 
 CPU idleness profiling
 ----------------------

diff --git a/blktrace.c b/blktrace.c
index 9cdbd3ca94df3006267227b6dd00f6481dd0fb96..14acc6991cd0343157605c2fd1875a2b4c57aeee 100644 (file)
--- a/blktrace.c
+++ b/blktrace.c
@@ -4,6 +4,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/ioctl.h>
+#include <unistd.h>
 #include <linux/fs.h>
 
 #include "flist.h"
@@ -614,6 +615,28 @@ err:
        return false;
 }
 
+static int init_merge_param_list(fio_fp64_t *vals, struct blktrace_cursor *bcs,
+                                int nr_logs, int def, size_t off)
+{
+       int i = 0, len = 0;
+
+       while (len < FIO_IO_U_LIST_MAX_LEN && vals[len].u.f != 0.0)
+               len++;
+
+       if (len && len != nr_logs)
+               return len;
+
+       for (i = 0; i < nr_logs; i++) {
+               int *val = (int *)((char *)&bcs[i] + off);
+               *val = def;
+               if (len)
+                       *val = (int)vals[i].u.f;
+       }
+
+       return 0;
+
+}
+
 static int find_earliest_io(struct blktrace_cursor *bcs, int nr_logs)
 {
        __u64 time = ~(__u64)0;
@@ -674,6 +697,8 @@ read_skip:
                goto read_skip;
        }
 
+       t->time = t->time * bc->scalar / 100;
+
        return ret;
 }
 
@@ -694,6 +719,15 @@ int merge_blktrace_iologs(struct thread_data *td)
        char *str, *ptr, *name, *merge_buf;
        int i, ret;
 
+       ret = init_merge_param_list(td->o.merge_blktrace_scalars, bcs, nr_logs,
+                                   100, offsetof(struct blktrace_cursor,
+                                                 scalar));
+       if (ret) {
+               log_err("fio: merge_blktrace_scalars(%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);
@@ -765,6 +799,7 @@ err_file:
 err_out_file:
        fflush(merge_fp);
        fclose(merge_fp);
+err_param:
        free(bcs);
 
        return ret;

diff --git a/blktrace.h b/blktrace.h
index 1b2bb76bbcd37a3ec24e59475390c999ba0666a7..cebd54d6a58969b463f03219d8129d2fc88db6fc 100644 (file)
--- a/blktrace.h
+++ b/blktrace.h
@@ -11,6 +11,7 @@ struct blktrace_cursor {
        int                     fd;     // blktrace file
        struct blk_io_trace     t;      // current io trace
        int                     swap;   // bitwise reverse required
+       int                     scalar; // scale percentage
 };
 
 bool is_blktrace(const char *, int *);

diff --git a/cconv.c b/cconv.c
index 45fff126081cd394c9c02dc0c811577b90747a42..dd136a086c61fd9dd97bea131ddc775c7082e4dc 100644 (file)
--- a/cconv.c
+++ b/cconv.c
@@ -306,6 +306,9 @@ void convert_thread_options_to_cpu(struct thread_options *o,
 
        for (i = 0; i < FIO_IO_U_LIST_MAX_LEN; i++)
                o->percentile_list[i].u.f = fio_uint64_to_double(le64_to_cpu(top->percentile_list[i].u.i));
+
+       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));
 #if 0
        uint8_t cpumask[FIO_TOP_STR_MAX];
        uint8_t verify_cpumask[FIO_TOP_STR_MAX];
@@ -568,6 +571,9 @@ void convert_thread_options_to_net(struct thread_options_pack *top,
 
        for (i = 0; i < FIO_IO_U_LIST_MAX_LEN; i++)
                top->percentile_list[i].u.i = __cpu_to_le64(fio_double_to_uint64(o->percentile_list[i].u.f));
+
+       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));
 #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 e28a1fa7b23699696c465399cf2f899d96ac92e1..620b6b3730f2432d00d7eec03675e23a533f2c85 100644 (file)
--- a/fio.1
+++ b/fio.1
@@ -2209,6 +2209,15 @@ intention here is to make the order of events consistent. This limits the
 influence of the scheduler compared to replaying multiple blktraces via
 concurrent jobs.
 .TP
+.BI merge_blktrace_scalars \fR=\fPfloat_list
+This is a percentage based option that is index paired with the list of files
+passed to \fBread_iolog\fR. When merging is performed, scale the time of each
+event by the corresponding amount. For example,
+`\-\-merge_blktrace_scalars="50:100"' runs the first trace in halftime and the
+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 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
@@ -3561,6 +3570,11 @@ $ fio \-\-read_iolog="<file1>:<file2>" \-\-merge_blktrace_file="<output_file>"
 .P
 Creating only the merged file can be done by passing the command line argument
 \fBmerge-blktrace-only\fR.
+.P
+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.
 .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 c0deffcb3a5eabf56629cb29a90039bfcf77f5c4..706f98fda4472455c8b49f0277d32f696110b22d 100644 (file)
--- a/options.c
+++ b/options.c
@@ -3207,6 +3207,16 @@ struct fio_option fio_options[FIO_MAX_OPTS] = {
                .category = FIO_OPT_C_IO,
                .group = FIO_OPT_G_IOLOG,
        },
+       {
+               .name   = "merge_blktrace_scalars",
+               .lname  = "Percentage to scale each trace",
+               .type   = FIO_OPT_FLOAT_LIST,
+               .off1   = offsetof(struct thread_options, merge_blktrace_scalars),
+               .maxlen = FIO_IO_U_LIST_MAX_LEN,
+               .help   = "Percentage to scale each 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 ebd059076875c47b106e0c0c000f7163673cfc8c..3d5e0115954fd40f09b374ba615427845dc7674e 100644 (file)
--- a/server.h
+++ b/server.h
@@ -48,7 +48,7 @@ struct fio_net_cmd_reply {
 };
 
 enum {
-       FIO_SERVER_VER                  = 75,
+       FIO_SERVER_VER                  = 76,
 
        FIO_SERVER_MAX_FRAGMENT_PDU     = 1024,
        FIO_SERVER_MAX_CMD_MB           = 2048,

diff --git a/thread_options.h b/thread_options.h
index 8b06f55a415efcddfda3dbdc9fa50640a9ff761a..f77574949d5f45c5d28880871cde5067d1922915 100644 (file)
--- a/thread_options.h
+++ b/thread_options.h
@@ -259,6 +259,7 @@ struct thread_options {
        bool read_iolog_chunked;
        char *write_iolog_file;
        char *merge_blktrace_file;
+       fio_fp64_t merge_blktrace_scalars[FIO_IO_U_LIST_MAX_LEN];
 
        unsigned int write_bw_log;
        unsigned int write_lat_log;
@@ -542,6 +543,7 @@ struct thread_options_pack {
        uint8_t read_iolog_file[FIO_TOP_STR_MAX];
        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];
 
        uint32_t write_bw_log;
        uint32_t write_lat_log;