135 lines
4.0 KiB
Diff
135 lines
4.0 KiB
Diff
From: Tom Zanussi <tom.zanussi@linux.intel.com>
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Date: Wed, 6 Dec 2017 16:38:15 -0600
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Subject: [PATCH 34/37] tracing: Add a clock attribute for hist triggers
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.14/older/patches-4.14.6-rt7.tar.xz
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The default clock if timestamps are used in a histogram is "global".
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If timestamps aren't used, the clock is irrelevant.
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Use the "clock=" param only if you want to override the default
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"global" clock for a histogram with timestamps.
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Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
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Signed-off-by: Rajvi Jingar <rajvi.jingar@intel.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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Documentation/trace/histogram.txt | 11 +++++++++
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kernel/trace/trace_events_hist.c | 42 +++++++++++++++++++++++++++++++++++---
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2 files changed, 49 insertions(+), 4 deletions(-)
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--- a/Documentation/trace/histogram.txt
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+++ b/Documentation/trace/histogram.txt
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@@ -1671,7 +1671,16 @@ specification. In support of this overa
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it is in units of nanoseconds; appending '.usecs' to a
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common_timestamp field changes the units to microseconds.
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-These features are decribed in more detail in the following sections.
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+A note on inter-event timestamps: If common_timestamp is used in a
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+histogram, the trace buffer is automatically switched over to using
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+absolute timestamps and the "global" trace clock, in order to avoid
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+bogus timestamp differences with other clocks that aren't coherent
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+across CPUs. This can be overridden by specifying one of the other
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+trace clocks instead, using the "clock=XXX" hist trigger attribute,
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+where XXX is any of the clocks listed in the tracing/trace_clock
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+pseudo-file.
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+
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+These features are described in more detail in the following sections.
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2.2.1 Histogram Variables
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-------------------------
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--- a/kernel/trace/trace_events_hist.c
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+++ b/kernel/trace/trace_events_hist.c
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@@ -242,6 +242,7 @@ struct hist_trigger_attrs {
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char *vals_str;
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char *sort_key_str;
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char *name;
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+ char *clock;
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bool pause;
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bool cont;
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bool clear;
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@@ -1792,6 +1793,7 @@ static void destroy_hist_trigger_attrs(s
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kfree(attrs->sort_key_str);
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kfree(attrs->keys_str);
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kfree(attrs->vals_str);
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+ kfree(attrs->clock);
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kfree(attrs);
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}
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@@ -1847,6 +1849,19 @@ static int parse_assignment(char *str, s
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ret = -ENOMEM;
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goto out;
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}
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+ } else if (strncmp(str, "clock=", strlen("clock=")) == 0) {
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+ strsep(&str, "=");
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+ if (!str) {
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+ ret = -EINVAL;
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+ goto out;
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+ }
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+
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+ str = strstrip(str);
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+ attrs->clock = kstrdup(str, GFP_KERNEL);
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+ if (!attrs->clock) {
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+ ret = -ENOMEM;
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+ goto out;
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+ }
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} else if (strncmp(str, "size=", strlen("size=")) == 0) {
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int map_bits = parse_map_size(str);
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@@ -1911,6 +1926,14 @@ static struct hist_trigger_attrs *parse_
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goto free;
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}
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+ if (!attrs->clock) {
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+ attrs->clock = kstrdup("global", GFP_KERNEL);
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+ if (!attrs->clock) {
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+ ret = -ENOMEM;
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+ goto free;
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+ }
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+ }
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+
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return attrs;
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free:
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destroy_hist_trigger_attrs(attrs);
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@@ -4937,6 +4960,8 @@ static int event_hist_trigger_print(stru
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seq_puts(m, ".descending");
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}
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seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));
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+ if (hist_data->enable_timestamps)
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+ seq_printf(m, ":clock=%s", hist_data->attrs->clock);
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print_actions_spec(m, hist_data);
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@@ -5204,7 +5229,6 @@ static int hist_register_trigger(char *g
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data->paused = true;
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if (named_data) {
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- destroy_hist_data(data->private_data);
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data->private_data = named_data->private_data;
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set_named_trigger_data(data, named_data);
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data->ops = &event_hist_trigger_named_ops;
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@@ -5216,10 +5240,22 @@ static int hist_register_trigger(char *g
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goto out;
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}
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- ret++;
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+ if (hist_data->enable_timestamps) {
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+ char *clock = hist_data->attrs->clock;
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+
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+ ret = tracing_set_clock(file->tr, hist_data->attrs->clock);
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+ if (ret) {
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+ hist_err("Couldn't set trace_clock: ", clock);
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+ goto out;
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+ }
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- if (hist_data->enable_timestamps)
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tracing_set_time_stamp_abs(file->tr, true);
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+ }
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+
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+ if (named_data)
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+ destroy_hist_data(hist_data);
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+
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+ ret++;
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out:
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return ret;
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}
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