Re: [PATCH v4 3/7] perf tools: Enable overwrite settings

From: Arnaldo Carvalho de Melo
Date: Tue May 24 2016 - 14:40:42 EST

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Em Tue, May 24, 2016 at 02:29:00AM +0000, Wang Nan escreveu:
> This patch allows following config terms and option:
>
> Globally setting events to overwrite;
>
> # perf record --overwrite ...
>
> Set specific events to be overwrite or no-overwrite.
>
> # perf record --event cycles/overwrite/ ...
> # perf record --event cycles/no-overwrite/ ...

So, based on this chunk of documentation in this patch:

<quote>
Perf dumps data from overwritable ring buffer when switching output (see
--switch-output) and before terminate.
</>

I tried:

No --overwrite:

# perf record -e syscalls:*enter_nanosleep* usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.019 MB perf.data (1 samples) ]
# perf evlist -v
syscalls:sys_enter_nanosleep: type: 2, size: 112, config: 0x132, { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|CPU|PERIOD|RAW, disabled: 1, inherit: 1, mmap: 1, comm: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1
# Tip: use 'perf evlist --trace-fields' to show fields for tracepoint events
# perf script
usleep 29416 [002] 220099.782982: syscalls:sys_enter_nanosleep: rqtp: 0x7ffc21f73cc0, rmtp: 0x00000000

Now I went on to try this new --overwrite thing:

# perf record --overwrite -e syscalls:*enter_nanosleep* usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.019 MB perf.data ]
# perf evlist -v
syscalls:sys_enter_nanosleep: type: 2, size: 112, config: 0x132, { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|CPU|PERIOD|RAW, disabled: 1, inherit: 1, mmap: 1, comm: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, write_backward: 1
# Tip: use 'perf evlist --trace-fields' to show fields for tracepoint events
# perf script
#

So it hasn't recorded anything at anytime, i.e. I expected, based on the
documentation provided, that it would get what was in its buffer, to be written,
i.e. the single "syscalls:sys_enter_nanosleep" event that took place in that
workload.

So I'm now trying it together with --switch-output, but I just get one
timestamp suffixed perf.data file, empty, without that event that I know took
place.

Care to ellaborate here?

- Arnaldo

> Add missing config terms and update config term array size because the
> longest string length is changed.
>
> For overwritable events, automatically select attr.write_backward since
> perf requires it to be backward for reading.
>
> Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
> Signed-off-by: He Kuang <hekuang@xxxxxxxxxx>
> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: Zefan Li <lizefan@xxxxxxxxxx>
> Cc: pi3orama@xxxxxxx
> ---
> tools/perf/Documentation/perf-record.txt | 14 ++++++++++++++
> tools/perf/builtin-record.c | 1 +
> tools/perf/perf.h | 1 +
> tools/perf/util/evsel.c | 12 ++++++++++++
> tools/perf/util/evsel.h | 2 ++
> tools/perf/util/parse-events.c | 20 ++++++++++++++++++--
> tools/perf/util/parse-events.h | 2 ++
> tools/perf/util/parse-events.l | 2 ++
> 8 files changed, 52 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 8dbee83..f5cb932 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -360,6 +360,20 @@ particular perf.data snapshot should be kept or not.
>
> Implies --timestamp-filename, --no-buildid and --no-buildid-cache.
>
> +--overwrite::
> +Makes all events use overwritable ring buffer. Event with overwritable ring
> +buffer works like a flight recorder: when buffer gets full, instead of dumping
> +records into output file, kernel overwrites old records silently. Perf dumps
> +data from overwritable ring buffer when switching output (see --switch-output)
> +and before terminate.
> +
> +Perf behaves like a daemon when '--overwrite' and '--switch-output' are
> +provided. It record and drop events in background, and dumps data when
> +something unusual is detected.
> +
> +'overwrite' attribute can also be set or canceled for specific event using
> +config terms like 'cycles/overwrite/' and 'instructions/no-overwrite/'.
> +
> 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 d4cf1b0..9611380 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1310,6 +1310,7 @@ struct option __record_options[] = {
> OPT_BOOLEAN_SET('i', "no-inherit", &record.opts.no_inherit,
> &record.opts.no_inherit_set,
> "child tasks do not inherit counters"),
> + OPT_BOOLEAN(0, "overwrite", &record.opts.overwrite, "use overwrite mode"),
> OPT_UINTEGER('F', "freq", &record.opts.user_freq, "profile at this frequency"),
> OPT_CALLBACK('m', "mmap-pages", &record.opts, "pages[,pages]",
> "number of mmap data pages and AUX area tracing mmap pages",
> diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> index cd8f1b1..608b42b 100644
> --- a/tools/perf/perf.h
> +++ b/tools/perf/perf.h
> @@ -59,6 +59,7 @@ struct record_opts {
> bool record_switch_events;
> bool all_kernel;
> bool all_user;
> + bool overwrite;
> unsigned int freq;
> unsigned int mmap_pages;
> unsigned int auxtrace_mmap_pages;
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 02c177d..6330a4f 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -671,11 +671,22 @@ static void apply_config_terms(struct perf_evsel *evsel,
> */
> attr->inherit = term->val.inherit ? 1 : 0;
> break;
> + case PERF_EVSEL__CONFIG_TERM_OVERWRITE:
> + evsel->overwrite = term->val.overwrite ? 1 : 0;
> + break;
> default:
> break;
> }
> }
>
> + /*
> + * Set backward after config term processing because it is
> + * possible to set overwrite globally, without config
> + * terms.
> + */
> + if (evsel->overwrite)
> + attr->write_backward = 1;
> +
> /* User explicitly set per-event callgraph, clear the old setting and reset. */
> if ((callgraph_buf != NULL) || (dump_size > 0)) {
>
> @@ -747,6 +758,7 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts,
>
> attr->sample_id_all = perf_missing_features.sample_id_all ? 0 : 1;
> attr->inherit = !opts->no_inherit;
> + evsel->overwrite = opts->overwrite;
>
> perf_evsel__set_sample_bit(evsel, IP);
> perf_evsel__set_sample_bit(evsel, TID);
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index c1f1015..bce99fa 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -44,6 +44,7 @@ enum {
> PERF_EVSEL__CONFIG_TERM_CALLGRAPH,
> PERF_EVSEL__CONFIG_TERM_STACK_USER,
> PERF_EVSEL__CONFIG_TERM_INHERIT,
> + PERF_EVSEL__CONFIG_TERM_OVERWRITE,
> PERF_EVSEL__CONFIG_TERM_MAX,
> };
>
> @@ -57,6 +58,7 @@ struct perf_evsel_config_term {
> char *callgraph;
> u64 stack_user;
> bool inherit;
> + bool overwrite;
> } val;
> };
>
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index bcbc983..85f813d 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -900,6 +900,8 @@ static const char *config_term_names[__PARSE_EVENTS__TERM_TYPE_NR] = {
> [PARSE_EVENTS__TERM_TYPE_STACKSIZE] = "stack-size",
> [PARSE_EVENTS__TERM_TYPE_NOINHERIT] = "no-inherit",
> [PARSE_EVENTS__TERM_TYPE_INHERIT] = "inherit",
> + [PARSE_EVENTS__TERM_TYPE_OVERWRITE] = "overwrite",
> + [PARSE_EVENTS__TERM_TYPE_NOOVERWRITE] = "no-overwrite",
> };
>
> static bool config_term_shrinked;
> @@ -992,6 +994,12 @@ do { \
> case PARSE_EVENTS__TERM_TYPE_NOINHERIT:
> CHECK_TYPE_VAL(NUM);
> break;
> + case PARSE_EVENTS__TERM_TYPE_OVERWRITE:
> + CHECK_TYPE_VAL(NUM);
> + break;
> + case PARSE_EVENTS__TERM_TYPE_NOOVERWRITE:
> + CHECK_TYPE_VAL(NUM);
> + break;
> case PARSE_EVENTS__TERM_TYPE_NAME:
> CHECK_TYPE_VAL(STR);
> break;
> @@ -1040,6 +1048,8 @@ static int config_term_tracepoint(struct perf_event_attr *attr,
> case PARSE_EVENTS__TERM_TYPE_STACKSIZE:
> case PARSE_EVENTS__TERM_TYPE_INHERIT:
> case PARSE_EVENTS__TERM_TYPE_NOINHERIT:
> + case PARSE_EVENTS__TERM_TYPE_OVERWRITE:
> + case PARSE_EVENTS__TERM_TYPE_NOOVERWRITE:
> return config_term_common(attr, term, err);
> default:
> if (err) {
> @@ -1109,6 +1119,12 @@ do { \
> case PARSE_EVENTS__TERM_TYPE_NOINHERIT:
> ADD_CONFIG_TERM(INHERIT, inherit, term->val.num ? 0 : 1);
> break;
> + case PARSE_EVENTS__TERM_TYPE_OVERWRITE:
> + ADD_CONFIG_TERM(OVERWRITE, overwrite, term->val.num ? 1 : 0);
> + break;
> + case PARSE_EVENTS__TERM_TYPE_NOOVERWRITE:
> + ADD_CONFIG_TERM(OVERWRITE, overwrite, term->val.num ? 0 : 1);
> + break;
> default:
> break;
> }
> @@ -2322,9 +2338,9 @@ static void config_terms_list(char *buf, size_t buf_sz)
> char *parse_events_formats_error_string(char *additional_terms)
> {
> char *str;
> - /* "branch_type" is the longest name */
> + /* "no-overwrite" is the longest name */
> char static_terms[__PARSE_EVENTS__TERM_TYPE_NR *
> - (sizeof("branch_type") - 1)];
> + (sizeof("no-overwrite") - 1)];
>
> config_terms_list(static_terms, sizeof(static_terms));
> /* valid terms */
> diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
> index d740c3c..f341d9d 100644
> --- a/tools/perf/util/parse-events.h
> +++ b/tools/perf/util/parse-events.h
> @@ -68,6 +68,8 @@ enum {
> PARSE_EVENTS__TERM_TYPE_STACKSIZE,
> PARSE_EVENTS__TERM_TYPE_NOINHERIT,
> PARSE_EVENTS__TERM_TYPE_INHERIT,
> + PARSE_EVENTS__TERM_TYPE_NOOVERWRITE,
> + PARSE_EVENTS__TERM_TYPE_OVERWRITE,
> __PARSE_EVENTS__TERM_TYPE_NR,
> };
>
> diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
> index 1477fbc..cc4c426 100644
> --- a/tools/perf/util/parse-events.l
> +++ b/tools/perf/util/parse-events.l
> @@ -201,6 +201,8 @@ call-graph { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_CALLGRAPH); }
> stack-size { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_STACKSIZE); }
> inherit { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_INHERIT); }
> no-inherit { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_NOINHERIT); }
> +overwrite { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_OVERWRITE); }
> +no-overwrite { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_NOOVERWRITE); }
> , { return ','; }
> "/" { BEGIN(INITIAL); return '/'; }
> {name_minus} { return str(yyscanner, PE_NAME); }
> --
> 1.8.3.4

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