WSL2-Linux-Kernel/tools/perf/Documentation
Kirill Smelkov acac03fa15 perf record: Add "nodelay" mode, disabled by default
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>
2011-01-13 11:38:44 -02:00
..
Makefile perf: Make the install relative to DESTDIR if specified 2010-03-11 14:08:11 +01:00
asciidoc.conf perf_counter tools: Move from Documentation/perf_counter/ to tools/perf/ 2009-06-06 20:33:43 +02:00
examples.txt perf: Rename perf-examples.txt to examples.txt 2009-08-17 10:43:42 +02:00
manpage-1.72.xsl perf_counter tools: Move from Documentation/perf_counter/ to tools/perf/ 2009-06-06 20:33:43 +02:00
manpage-base.xsl perf_counter tools: Move from Documentation/perf_counter/ to tools/perf/ 2009-06-06 20:33:43 +02:00
manpage-bold-literal.xsl perf_counter tools: Move from Documentation/perf_counter/ to tools/perf/ 2009-06-06 20:33:43 +02:00
manpage-normal.xsl perf_counter tools: Move from Documentation/perf_counter/ to tools/perf/ 2009-06-06 20:33:43 +02:00
manpage-suppress-sp.xsl perf_counter tools: Move from Documentation/perf_counter/ to tools/perf/ 2009-06-06 20:33:43 +02:00
perf-annotate.txt perf annotate: Document missing options. 2010-12-01 18:22:45 -02:00
perf-archive.txt perf archive: Add documentation 2010-01-20 08:54:58 +01:00
perf-bench.txt perf tools: Fixup minor doc formatting issues 2010-05-05 11:23:27 -03:00
perf-buildid-cache.txt perf man pages: Fix cut'n'paste error 2010-07-28 11:30:10 -03:00
perf-buildid-list.txt perf buildid-list: Document missing options 2010-12-01 18:22:45 -02:00
perf-diff.txt perf symbols: Add symfs option for off-box analysis using specified tree 2010-12-21 20:17:51 -02:00
perf-help.txt perf_counter tools: Move from Documentation/perf_counter/ to tools/perf/ 2009-06-06 20:33:43 +02:00
perf-inject.txt perf inject: Add missing bits 2010-05-04 10:48:22 -03:00
perf-kmem.txt perf tools: Fixup minor doc formatting issues 2010-05-05 11:23:27 -03:00
perf-kvm.txt perf kvm: Document missing options 2010-12-01 18:22:46 -02:00
perf-list.txt perf tools: Document event modifiers 2010-10-23 15:31:20 -02:00
perf-lock.txt perf lock: Document missing options 2010-12-01 18:22:46 -02:00
perf-probe.txt perf probe: Fix line range description since a single file is allowed 2010-12-21 16:20:12 -02:00
perf-record.txt perf record: Add "nodelay" mode, disabled by default 2011-01-13 11:38:44 -02:00
perf-report.txt perf symbols: Add symfs option for off-box analysis using specified tree 2010-12-21 20:17:51 -02:00
perf-sched.txt perf sched: Document missing options 2010-12-01 18:22:48 -02:00
perf-script-perl.txt perf: Rename 'perf trace' to 'perf script' 2010-11-16 19:37:44 +01:00
perf-script-python.txt perf: Rename 'perf trace' to 'perf script' 2010-11-16 19:37:44 +01:00
perf-script.txt Merge branch 'perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux-2.6 into perf/core 2010-12-02 11:20:11 +01:00
perf-stat.txt perf stat: Add csv-style output 2010-12-01 19:47:41 -02:00
perf-test.txt perf test: Fix spelling mistake in documentation 2010-12-01 18:22:49 -02:00
perf-timechart.txt perf symbols: Add symfs option for off-box analysis using specified tree 2010-12-21 20:17:51 -02:00
perf-top.txt perf top: Document missing options 2010-12-01 18:22:48 -02:00
perf.txt perf: Fix few typos + cosmetics 2010-01-13 17:39:44 +01:00