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perf record: Add "nodelay" mode, disabled by default

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Sometimes there is a need to use perf in "live-log" mode. The problem
is, for seldom events, actual info output is largely delayed because
perf-record reads sample data in whole pages.

So for such scenarious, add flag for perf-record to go in "nodelay"
mode. To track e.g. what's going on in icmp_rcv while ping is running
Use it with something like this:

(1) $ perf probe -L icmp_rcv | grep -U8 '^ *43\>'
                                    goto error;
                    }
         38         if (!pskb_pull(skb, sizeof(*icmph)))
                            goto error;
                    icmph = icmp_hdr(skb);

         43         ICMPMSGIN_INC_STATS_BH(net, icmph->type);
                    /*
                     *      18 is the highest 'known' ICMP type. Anything else is a mystery
                     *
                     *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
                     *                discarded.
                     */
         50         if (icmph->type > NR_ICMP_TYPES)
                            goto error;

    $ perf probe icmp_rcv:43 'type=icmph->type'

(2) $ cat trace-icmp.py
    [...]
    def trace_begin():
            print "in trace_begin"

    def trace_end():
            print "in trace_end"

    def probe__icmp_rcv(event_name, context, common_cpu,
            common_secs, common_nsecs, common_pid, common_comm,
            __probe_ip, type):
                    print_header(event_name, common_cpu, common_secs, common_nsecs,
                            common_pid, common_comm)

                    print "__probe_ip=%u, type=%u\n" % \
                    (__probe_ip, type),
    [...]

(3) $ perf record -a -D -e probe:icmp_rcv -o - | \
      perf script -i - -s trace-icmp.py

Thanks to Peter Zijlstra for pointing how to do it.

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <20110112140613.GA11698@tugrik.mns.mnsspb.ru>
Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Kirill Smelkov 2011-01-12 17:59:36 +03:00 committed by Arnaldo Carvalho de Melo
parent 9710118bd4
commit acac03fa15
2 changed files with 11 additions and 0 deletions
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3
tools/perf/Documentation/perf-record.txt
View File

@ -61,6 +61,9 @@ OPTIONS
-r::
--realtime=::
Collect data with this RT SCHED_FIFO priority.
-D::
--no-delay::
Collect data without buffering.
-A::
--append::
Append to the output file to do incremental profiling.

8
tools/perf/builtin-record.c
View File

@ -49,6 +49,7 @@ static int pipe_output = 0;
static const char *output_name = "perf.data";
static int group = 0;
static int realtime_prio = 0;
static bool nodelay = false;
static bool raw_samples = false;
static bool sample_id_all_avail = true;
static bool system_wide = false;
@ -307,6 +308,11 @@ static void create_counter(struct perf_evsel *evsel, int cpu)
attr->sample_type |= PERF_SAMPLE_CPU;
}
if (nodelay) {
attr->watermark = 0;
attr->wakeup_events = 1;
}
attr->mmap = track;
attr->comm = track;
attr->inherit = !no_inherit;
@ -843,6 +849,8 @@ const struct option record_options[] = {
"record events on existing thread id"),
OPT_INTEGER('r', "realtime", &realtime_prio,
"collect data with this RT SCHED_FIFO priority"),
OPT_BOOLEAN('D', "no-delay", &nodelay,
"collect data without buffering"),
OPT_BOOLEAN('R', "raw-samples", &raw_samples,
"collect raw sample records from all opened counters"),
OPT_BOOLEAN('a', "all-cpus", &system_wide,