linux-kernel - Re: [PATCH v2 02/14] perf mem: Introduce weak function perf_mem_events_

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Date:   Fri, 4 Sep 2020 08:34:47 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Kemeng Shi <shikemeng@...wei.com>,
        James Clark <james.clark@....com>,
        Wei Li <liwei391@...wei.com>, Al Grant <Al.Grant@....com>,
        Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Leach <mike.leach@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 02/14] perf mem: Introduce weak function
 perf_mem_events__ptr()

Hi Jiri,

On Thu, Sep 03, 2020 at 03:50:54PM +0200, Jiri Olsa wrote:
> On Tue, Sep 01, 2020 at 09:38:03AM +0100, Leo Yan wrote:
> 
> SNIP
> 
> > @@ -2941,30 +2942,38 @@ static int perf_c2c__record(int argc, const char **argv)
> >  	rec_argv[i++] = "record";
> >  
> >  	if (!event_set) {
> > -		perf_mem_events[PERF_MEM_EVENTS__LOAD].record  = true;
> > -		perf_mem_events[PERF_MEM_EVENTS__STORE].record = true;
> > +		e = perf_mem_events__ptr(PERF_MEM_EVENTS__LOAD);
> > +		e->record = true;
> > +
> > +		e = perf_mem_events__ptr(PERF_MEM_EVENTS__STORE);
> > +		e->record = true;
> >  	}
> >  
> > -	if (perf_mem_events[PERF_MEM_EVENTS__LOAD].record)
> > +	e = perf_mem_events__ptr(PERF_MEM_EVENTS__LOAD);
> > +	if (e->record)
> >  		rec_argv[i++] = "-W";
> >  
> >  	rec_argv[i++] = "-d";
> >  	rec_argv[i++] = "--phys-data";
> >  	rec_argv[i++] = "--sample-cpu";
> >  
> > -	for (j = 0; j < PERF_MEM_EVENTS__MAX; j++) {
> > -		if (!perf_mem_events[j].record)
> > +	j = 0;
> > +	while ((e = perf_mem_events__ptr(j)) != NULL) {
> > +		if (!e->record) {
> 
> you could keep the above 'for loop' in here, it seems better
> than taking care of j++

Actually in patch v1 I did this way :)  I followed James' suggestion to
encapsulate PERF_MEM_EVENTS__MAX into perf_mem_events__ptr(), thus
builtin-mem.c and buildin-c2c.c are not necessary to use
PERF_MEM_EVENTS__MAX in the loop and only needs to detect if the
pointer is NULL or not when return from perf_mem_events__ptr().

How about change as below?

        for (j = 0; (e = perf_mem_events__ptr(j)) != NULL; j++) {
                [...]
        }

If you still think this is not good, I will change back to the old
code style in next spin

Thanks for reviewing!

Leo

> > +			j++;
> >  			continue;
> > +		}
> >  
> > -		if (!perf_mem_events[j].supported) {
> > +		if (!e->supported) {
> >  			pr_err("failed: event '%s' not supported\n",
> > -			       perf_mem_events[j].name);
> > +			       perf_mem_events__name(j));
> >  			free(rec_argv);
> >  			return -1;
> >  		}
> >  
> >  		rec_argv[i++] = "-e";
> >  		rec_argv[i++] = perf_mem_events__name(j);
> > +		j++;
> >  	}
> >  
> >  	if (all_user)
> 
> SNIP
> 
> > @@ -100,11 +106,14 @@ static int __cmd_record(int argc, const char **argv, struct perf_mem *mem)
> >  	if (mem->phys_addr)
> >  		rec_argv[i++] = "--phys-data";
> >  
> > -	for (j = 0; j < PERF_MEM_EVENTS__MAX; j++) {
> > -		if (!perf_mem_events[j].record)
> > +	j = 0;
> > +	while ((e = perf_mem_events__ptr(j)) != NULL) {
> > +		if (!e->record) {
> 
> same here
> 
> thanks,
> jirka
> 
> > +			j++;
> >  			continue;
> > +		}
> >  
> > -		if (!perf_mem_events[j].supported) {
> > +		if (!e->supported) {
> >  			pr_err("failed: event '%s' not supported\n",
> >  			       perf_mem_events__name(j));
> >  			free(rec_argv);
> > @@ -113,6 +122,7 @@ static int __cmd_record(int argc, const char **argv, struct perf_mem *mem)
> >  
> >  		rec_argv[i++] = "-e";
> >  		rec_argv[i++] = perf_mem_events__name(j);
> > +		j++;
> 
> SNIP
>