> The meaning of perf record's "overwrite" option and many "overwrite" in
> source code are not clear. In perf's code, the 'overwrite' has 2 meanings:
> 1. Make ringbuffer readonly (perf_evlist__mmap_ex's argument).
> 2. Set evsel's "backward" attribute (in apply_config_terms).
>
> perf record doesn't use meaning 1 at all, but have a overwrite option, its
> real meaning is setting backward.
>
I don't understand here.
'overwrite' has 2 meanings. perf record only support 1.
It should be a bug, and need to be fixed.
Why do we need a new mode?
I think a new mode just make the codes more complex.
Thanks,
Kan
> This patch separates these two concepts, introduce 'flightrecorder' mode
> which is what we really want. It combines these 2 concept together, wraps
> them into a record mode. In flight recorder mode, perf only dumps data
> before
> something happen.
>
> Signed-off-by: Wang Nan <wangn...@huawei.com>
> ---
> tools/perf/Documentation/perf-record.txt | 8 ++++----
> tools/perf/builtin-record.c | 4 ++--
> tools/perf/perf.h | 2 +-
> tools/perf/util/evsel.c | 6 +++---
> tools/perf/util/evsel.h | 4 ++--
> tools/perf/util/parse-events.c | 20 ++++++++++----------
> tools/perf/util/parse-events.h | 4 ++--
> tools/perf/util/parse-events.l | 4 ++--
> 8 files changed, 26 insertions(+), 26 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-record.txt
> b/tools/perf/Documentation/perf-record.txt
> index 5a626ef..463c2d3 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -467,19 +467,19 @@ the beginning of record, collect them during
> finalizing an output file.
> The collected non-sample events reflects the status of the system when
> record is finished.
>
> ---overwrite::
> +--flight-recorder::
> Makes all events use an overwritable ring buffer. An overwritable ring
> buffer works like a flight recorder: when it gets full, the kernel will
> overwrite the oldest records, that thus will never make it to the
> perf.data file.
>
> -When '--overwrite' and '--switch-output' are used perf records and drops
> +When '--flight-recorder' and '--switch-output' are used perf records and
> drops
> events until it receives a signal, meaning that something unusual was
> detected that warrants taking a snapshot of the most current events,
> those fitting in the ring buffer at that moment.
>
> -'overwrite' attribute can also be set or canceled for an event using
> -config terms. For example: 'cycles/overwrite/' and 'instructions/no-
> overwrite/'.
> +'flightrecorder' attribute can also be set or canceled separately for an
> event
> using
> +config terms. For example: 'cycles/flightrecorder/' and 'instructions/no-
> flightrecorder/'.
>
> Implies --tail-synthesize.
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index f4d9fc5..315ea09 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1489,7 +1489,7 @@ static struct option __record_options[] = {
> "child tasks do not inherit counters"),
> OPT_BOOLEAN(0, "tail-synthesize", &record.opts.tail_synthesize,
> "synthesize non-sample events at the end of output"),
> - OPT_BOOLEAN(0, "overwrite", &record.opts.overwrite, "use
> overwrite mode"),
> + OPT_BOOLEAN(0, "flight-recoder", &record.opts.flight_recorder,
> "use flight recoder 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",
> @@ -1733,7 +1733,7 @@ int cmd_record(int argc, const char **argv)
> }
> }
>
> - if (record.opts.overwrite)
> + if (record.opts.flight_recorder)
> record.opts.tail_synthesize = true;
>
> if (rec->evlist->nr_entries == 0 &&
> diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> index fbb0a9c..a7f7618 100644
> --- a/tools/perf/perf.h
> +++ b/tools/perf/perf.h
> @@ -57,7 +57,7 @@ struct record_opts {
> bool all_kernel;
> bool all_user;
> bool tail_synthesize;
> - bool overwrite;
> + bool flight_recorder;
> bool ignore_missing_thread;
> unsigned int freq;
> unsigned int mmap_pages;
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index f894893..0e1e8e8 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -772,8 +772,8 @@ static void apply_config_terms(struct perf_evsel
> *evsel,
> */
> attr->inherit = term->val.inherit ? 1 : 0;
> break;
> - case PERF_EVSEL__CONFIG_TERM_OVERWRITE:
> - attr->write_backward = term->val.overwrite ? 1 : 0;
> + case PERF_EVSEL__CONFIG_TERM_FLIGHTRECORDER:
> + attr->write_backward = term->val.flightrecorder ? 1 :
> 0;
> break;
> default:
> break;
> @@ -856,7 +856,7 @@ 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;
> - attr->write_backward = opts->overwrite ? 1 : 0;
> + attr->write_backward = opts->flight_recorder ? 1 : 0;
>
> 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 64782b1..115b637 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -45,7 +45,7 @@ enum {
> PERF_EVSEL__CONFIG_TERM_STACK_USER,
> PERF_EVSEL__CONFIG_TERM_INHERIT,
> PERF_EVSEL__CONFIG_TERM_MAX_STACK,
> - PERF_EVSEL__CONFIG_TERM_OVERWRITE,
> + PERF_EVSEL__CONFIG_TERM_FLIGHTRECORDER,
> PERF_EVSEL__CONFIG_TERM_DRV_CFG,
> PERF_EVSEL__CONFIG_TERM_BRANCH,
> PERF_EVSEL__CONFIG_TERM_MAX,
> @@ -63,7 +63,7 @@ struct perf_evsel_config_term {
> u64 stack_user;
> int max_stack;
> bool inherit;
> - bool overwrite;
> + bool flightrecorder;
> char *branch;
> } val;
> };
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 04f35db..61ae3d3 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -914,8 +914,8 @@ static const char
> *config_term_names[__PARSE_EVENTS__TERM_TYPE_NR] = {
> [PARSE_EVENTS__TERM_TYPE_NOINHERIT] = "no-inherit",
> [PARSE_EVENTS__TERM_TYPE_INHERIT] = "inherit",
> [PARSE_EVENTS__TERM_TYPE_MAX_STACK] = "max-stack",
> - [PARSE_EVENTS__TERM_TYPE_OVERWRITE] = "overwrite",
> - [PARSE_EVENTS__TERM_TYPE_NOOVERWRITE] = "no-
> overwrite",
> + [PARSE_EVENTS__TERM_TYPE_FLIGHTRECORDER] =
> "flightrecorder",
> + [PARSE_EVENTS__TERM_TYPE_NOFLIGHTRECORDER] = "no-
> flightrecorder",
> [PARSE_EVENTS__TERM_TYPE_DRV_CFG] = "driver-
> config",
> };
>
> @@ -1013,10 +1013,10 @@ do {
> \
> case PARSE_EVENTS__TERM_TYPE_NOINHERIT:
> CHECK_TYPE_VAL(NUM);
> break;
> - case PARSE_EVENTS__TERM_TYPE_OVERWRITE:
> + case PARSE_EVENTS__TERM_TYPE_FLIGHTRECORDER:
> CHECK_TYPE_VAL(NUM);
> break;
> - case PARSE_EVENTS__TERM_TYPE_NOOVERWRITE:
> + case PARSE_EVENTS__TERM_TYPE_NOFLIGHTRECORDER:
> CHECK_TYPE_VAL(NUM);
> break;
> case PARSE_EVENTS__TERM_TYPE_NAME:
> @@ -1072,8 +1072,8 @@ static int config_term_tracepoint(struct
> perf_event_attr *attr,
> case PARSE_EVENTS__TERM_TYPE_INHERIT:
> case PARSE_EVENTS__TERM_TYPE_NOINHERIT:
> case PARSE_EVENTS__TERM_TYPE_MAX_STACK:
> - case PARSE_EVENTS__TERM_TYPE_OVERWRITE:
> - case PARSE_EVENTS__TERM_TYPE_NOOVERWRITE:
> + case PARSE_EVENTS__TERM_TYPE_FLIGHTRECORDER:
> + case PARSE_EVENTS__TERM_TYPE_NOFLIGHTRECORDER:
> return config_term_common(attr, term, err);
> default:
> if (err) {
> @@ -1149,11 +1149,11 @@ do {
> \
> case PARSE_EVENTS__TERM_TYPE_MAX_STACK:
> ADD_CONFIG_TERM(MAX_STACK, max_stack, term-
> >val.num);
> break;
> - case PARSE_EVENTS__TERM_TYPE_OVERWRITE:
> - ADD_CONFIG_TERM(OVERWRITE, overwrite, term-
> >val.num ? 1 : 0);
> + case PARSE_EVENTS__TERM_TYPE_FLIGHTRECORDER:
> + ADD_CONFIG_TERM(FLIGHTRECORDER,
> flightrecorder, term->val.num ? 1 : 0);
> break;
> - case PARSE_EVENTS__TERM_TYPE_NOOVERWRITE:
> - ADD_CONFIG_TERM(OVERWRITE, overwrite, term-
> >val.num ? 0 : 1);
> + case PARSE_EVENTS__TERM_TYPE_NOFLIGHTRECORDER:
> + ADD_CONFIG_TERM(FLIGHTRECORDER,
> flightrecorder, term->val.num ? 0 : 1);
> break;
> case PARSE_EVENTS__TERM_TYPE_DRV_CFG:
> ADD_CONFIG_TERM(DRV_CFG, drv_cfg, term-
> >val.str);
> diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
> index 3909ca0..cd0b4eae 100644
> --- a/tools/perf/util/parse-events.h
> +++ b/tools/perf/util/parse-events.h
> @@ -70,8 +70,8 @@ enum {
> PARSE_EVENTS__TERM_TYPE_NOINHERIT,
> PARSE_EVENTS__TERM_TYPE_INHERIT,
> PARSE_EVENTS__TERM_TYPE_MAX_STACK,
> - PARSE_EVENTS__TERM_TYPE_NOOVERWRITE,
> - PARSE_EVENTS__TERM_TYPE_OVERWRITE,
> + PARSE_EVENTS__TERM_TYPE_NOFLIGHTRECORDER,
> + PARSE_EVENTS__TERM_TYPE_FLIGHTRECORDER,
> PARSE_EVENTS__TERM_TYPE_DRV_CFG,
> __PARSE_EVENTS__TERM_TYPE_NR,
> };
> diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
> index 38a42bd..7710d6d 100644
> --- a/tools/perf/util/parse-events.l
> +++ b/tools/perf/util/parse-events.l
> @@ -251,8 +251,8 @@ stack-size { return term(yyscanner,
> PARSE_EVENTS__TERM_TYPE_STACKSIZE); }
> max-stack { return term(yyscanner,
> PARSE_EVENTS__TERM_TYPE_MAX_STACK); }
> 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); }
> +flightrecorder { return term(yyscanner,
> PARSE_EVENTS__TERM_TYPE_FLIGHTRECORDER); }
> +no-flightrecorder { return term(yyscanner,
> PARSE_EVENTS__TERM_TYPE_NOFLIGHTRECORDER); }
> , { return ','; }
> "/" { BEGIN(INITIAL); return '/'; }
> {name_minus} { return str(yyscanner, PE_NAME); }
> --
> 2.10.1
