RE: [PATCH 2/2] perf record: Replace 'overwrite' by 'flightrecorder' for better naming

["Liang, Kan" <kan.liang@intel.com>]

> 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 <wangnan0@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