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Message-ID: <20110617141425.GD25197@somewhere.redhat.com>
Date: Fri, 17 Jun 2011 16:14:29 +0200
From: Frederic Weisbecker <fweisbec@...il.com>
To: David Ahern <dsahern@...il.com>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
acme@...stprotocols.net, mingo@...e.hu, peterz@...radead.org,
paulus@...ba.org, tglx@...utronix.de
Subject: Re: [PATCH 4/6] perf record: add time-of-day option
On Tue, Jun 07, 2011 at 05:56:04PM -0600, David Ahern wrote:
> Use reftime event for initial correlation of perf_clock to
> time-of-day. Add timekeeping trace events to event list to
> capture jumps in time-of-day.
>
> Signed-off-by: David Ahern <dsahern@...il.com>
> ---
> tools/perf/Documentation/perf-record.txt | 3 +
> tools/perf/builtin-record.c | 102 +++++++++++++++++++++++++++++-
> 2 files changed, 104 insertions(+), 1 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 5a520f8..e4c87ba 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -148,6 +148,9 @@ an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must ha
> corresponding events, i.e., they always refer to events defined earlier on the command
> line.
>
> +--tod::
> +Collect data for displaying time-of-day strings when printing events.
> +
> SEE ALSO
> --------
> linkperf:perf-stat[1], linkperf:perf-list[1]
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 8e2c857..4f8d5f2 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -32,6 +32,9 @@
>
> #define FD(e, x, y) (*(int *)xyarray__entry(e->fd, x, y))
>
> +#define TRACE_TOD_SUBSYSTEM "timekeeping"
> +#define TRACE_TOD_SUBSYSTEM_LEN 11
> +
> enum write_mode_t {
> WRITE_FORCE,
> WRITE_APPEND
> @@ -65,6 +68,8 @@ static bool sample_address = false;
> static bool sample_time = false;
> static bool no_buildid = false;
> static bool no_buildid_cache = false;
> +static bool want_tod = false;
> +static u64 tod_sample_type;
> static struct perf_evlist *evsel_list;
>
> static long samples = 0;
> @@ -215,6 +220,9 @@ static void config_attr(struct perf_evsel *evsel, struct perf_evlist *evlist)
> attr->sample_type |= PERF_SAMPLE_CPU;
> }
>
> + if (want_tod)
> + attr->sample_type |= tod_sample_type;
> +
> if (nodelay) {
> attr->watermark = 0;
> attr->wakeup_events = 1;
> @@ -248,6 +256,86 @@ static bool perf_evlist__equal(struct perf_evlist *evlist,
> return true;
> }
>
> +static int perf_event__synthesize_reftime(perf_event__handler_t process)
> +{
> + union perf_event ev;
> + struct timespec tp;
> +
> + memset(&ev, 0, sizeof(ev));
> +
> + if (gettimeofday(&ev.reftime.tv, NULL) != 0) {
> + error("gettimeofday failed.\n");
> + return -1;
> + }
> + if (clock_gettime(CLOCK_MONOTONIC, &tp) != 0) {
> + error("clock_gettime(CLOCK_MONOTONIC) failed.\n");
> + return -1;
> + }
> + ev.reftime.nsec = (u64) tp.tv_sec * NSEC_PER_SEC + (u64) tp.tv_nsec;
> +
> + ev.header.type = PERF_RECORD_REFTIME;
> + ev.header.size = sizeof(ev.reftime);
> +
> + return process(&ev, NULL, session);
> +}
> +
> +static int add_timeofday_events(void)
> +{
> + int rc, i, len;
> + struct perf_event_attr attr;
> + struct perf_evsel *evsel;
> +
> + /* events that modify xtime */
> + const char *tod_events[] = {"settimeofday",
> + "timekeeping_inject_offset",
> + "timekeeping_inject_sleeptime",
> + NULL};
> +
> + i = 0;
> + rc = -1;
> + while (tod_events[i]) {
> + memset(&attr, 0, sizeof(attr));
> + len = strlen(tod_events[i]);
> +
> + if (parse_single_tracepoint_event(TRACE_TOD_SUBSYSTEM,
> + tod_events[i], len, &attr, NULL) == EVT_FAILED) {
> + error("Failed to parse event %s\n", tod_events[i]);
> + goto out;
> + }
> +
> + evsel = perf_evsel__new(&attr, evsel_list->nr_entries);
> + if (evsel == NULL)
> + return -1;
> +
> + perf_evlist__add(evsel_list, evsel);
> +
> + /* +2 for ':' delimiter and string terminator */
> + evsel->name = calloc(TRACE_TOD_SUBSYSTEM_LEN + len + 2, 1);
> + if (!evsel->name)
> + return -1;
> +
> + sprintf(evsel->name, "timekeeping:%s", tod_events[i]);
> +
> + tod_sample_type |= attr.sample_type;
> +
> + ++i;
> + }
> +
> + /*
> + * right now sample_type for all samples needs to be the same.
> + * tracepoints are collected at sample period 1 and hence do not
> + * request the period with the sample. However, default for record
> + * is cycles at a frequency. So, until this sample_type mess is
> + * fixed....
> + */
> + if (freq)
> + tod_sample_type |= PERF_SAMPLE_PERIOD;
> +
> + rc = 0;
> +out:
> + return rc;
> +}
So I feel uncomfortable with this tod_sample_type hack. I think we can't really continue
with this fixed sample_type per session given the kind of hacks that involves.
One thing we could do is to split session->sample_type into an array with one sample
type per event type (hardware, breakpoint, software, tracepoint).
And then each builtin tool can provide their constraints on top of these values:
- builtin-report wants sample_type[HARDWARE] == sample_type[SOFTWARE] == sample_type[TRACEPOINT] == sample_type[BREAKPOINT]
although that may be tunable by the time but we can start with that.
- builtin-script has no specific constraints, except that sample_type[i] meets what the user passed as a parameter
- etc..
Constraints can probably default to sample_type[i] == sample_type[i+1] to mimic the current behaviour. Then tools
can override that.
What do you think?
--
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