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From: Jiri Olsa <jolsa@redhat.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>, Jiri Olsa <jolsa@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Jonas Rabenstein <jonas.rabenstein@studium.uni-erlangen.de>,
	Nageswara R Sastry <nasastry@in.ibm.com>,
	Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Subject: Re: [PATCH] perf tools: Move precise_ip detection into perf_evsel__open
Date: Fri, 15 Mar 2019 15:52:25 +0100
Message-ID: <20190315145225.GC5200@krava> (raw)
In-Reply-To: <20190315143504.GA24482@kernel.org>

On Fri, Mar 15, 2019 at 11:35:04AM -0300, Arnaldo Carvalho de Melo wrote:

SNIP

> > +static void display_attr(struct perf_event_attr *attr)
> > +{
> > +	if (verbose >= 2) {
> > +		fprintf(stderr, "%.60s\n", graph_dotted_line);
> > +		fprintf(stderr, "perf_event_attr:\n");
> > +		perf_event_attr__fprintf(stderr, attr, __open_attr__fprintf, NULL);
> > +		fprintf(stderr, "%.60s\n", graph_dotted_line);
> > +	}
> > +}
> > +
> > +static int perf_event_open(struct perf_evsel *evsel,
> > +			   pid_t pid, int cpu, int group_fd,
> > +			   unsigned long flags)
> 
> 
> The patch is ok, but I think the naming of this function is too generic,
> so I'm renaming it to:
> 
> static int perf_evsel__open_adjust_precise_ip(struct perf_evsel *evsel,
> 					      pid_t pid, int cpu, int group_fd,
> 					      unsigned long flags)
> 
> Ok?

ok

> 
> The perf_evsel__open() code is already complex with that fallback
> mechanism, this is just one more way of fallbacking when asking the
> kernel for something that may fail.
> 
> In fact what happens if the precise_ip that is being asked _is_
> supported but sys_perf_event_open() fails because some other
> perf_event_attr attribute that is set is not supported? 

it's outside the scope of standard feature fallback code,
so we will try it for any possible fallback variant, so:

we will try all possible precise_ip (3,2,1,0) and they will
all fail because of the unsupported attribute - so we will
restore the precise_ip back and continue in standard fallback
code that will eventualy switch that attribute off

> 
> I see, it gets it back restored to what the user asked so that the
> standard fallback is tried, ok, I'll apply with just the rename for this
> function,

thanks,
jirka

  reply index

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-05 15:25 [PATCH 0/8] perf tools: Assorted fixes Jiri Olsa
2019-03-05 15:25 ` [PATCH 1/8] perf c2c: Fix c2c report for empty numa node Jiri Olsa
2019-03-09 20:05   ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2019-03-05 15:25 ` [PATCH 2/8] perf tools: Add error path into hist_entry__init Jiri Olsa
2019-03-09 20:06   ` [tip:perf/urgent] perf hist: " tip-bot for Jiri Olsa
2019-03-05 15:25 ` [PATCH 3/8] perf hist: Fix memory leak of srcline Jiri Olsa
2019-03-09 20:07   ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2019-03-05 15:25 ` [PATCH 4/8] perf tools: Read and store caps/max_precise in perf_pmu Jiri Olsa
2019-03-09 20:07   ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2019-03-05 15:25 ` [PATCH 5/8] perf tools: Get precise_ip from the pmu config Jiri Olsa
2019-03-05 16:13   ` Andi Kleen
2019-03-05 16:28     ` Jiri Olsa
2019-03-05 16:40       ` Andi Kleen
2019-03-07 15:35         ` [PATCHv2 " Jiri Olsa
2019-03-07 16:51           ` Andi Kleen
2019-03-07 22:32             ` Jiri Olsa
2019-03-14 14:01             ` Jiri Olsa
2019-03-14 15:49               ` Andi Kleen
2019-03-15 12:15                 ` [PATCH] perf tools: Move precise_ip detection into perf_evsel__open Jiri Olsa
2019-03-15 14:05                   ` Andi Kleen
2019-03-15 14:35                   ` Arnaldo Carvalho de Melo
2019-03-15 14:52                     ` Jiri Olsa [this message]
2019-03-23 15:04                       ` Jiri Olsa
2019-03-25 14:53                         ` Arnaldo Carvalho de Melo
2019-03-05 15:25 ` [PATCH 6/8] perf tools: Probe for precise_ip with simple attr Jiri Olsa
2019-03-09 20:08   ` [tip:perf/urgent] perf evsel: " tip-bot for Jiri Olsa
2019-03-05 15:25 ` [PATCH 7/8] perf tools: Fix double free in perf_data__close Jiri Olsa
2019-03-09 20:09   ` [tip:perf/urgent] perf session: " tip-bot for Jiri Olsa
2019-03-05 15:25 ` [PATCH 8/8] perf tools: Force perf_data__open|close zero data->file.path Jiri Olsa
2019-03-09 20:09   ` [tip:perf/urgent] perf data: " tip-bot for Jiri Olsa

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