linux-kernel - Re: [PATCH 03/15 V3] perf c2c: Shared data analyser

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Date:	Tue, 8 Apr 2014 10:22:26 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Namhyung Kim <namhyung@...il.com>
Cc:	acme@...stprotocols.net, LKML <linux-kernel@...r.kernel.org>,
	jolsa@...hat.com, jmario@...hat.com, fowles@...each.com,
	peterz@...radead.org, eranian@...gle.com, andi.kleen@...el.com,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Richard Fowles <rfowles@...hat.com>
Subject: Re: [PATCH 03/15 V3] perf c2c: Shared data analyser

On Tue, Apr 08, 2014 at 03:59:15PM +0900, Namhyung Kim wrote:
> Hi Don,
> 
> On Mon, 24 Mar 2014 15:36:54 -0400, Don Zickus wrote:
> > From: Arnaldo Carvalho de Melo <acme@...hat.com>
> >
> > This is the start of a new perf tool that will collect information about
> > memory accesses and analyse it to find things like hot cachelines, etc.
> 
> So why not integrating this into existing 'perf mem' command if it's all
> about analyzing memory accesses?

Our expectations were different.  We expeted to do system-wide analysis
with loads and stores.  With 'perf mem' you didn't have the ability to
anlayze both load and stores at the same time.

In all my private conversations with Stephane, Arnalado and Jiri, it was
never brought up.  We had just assumed that is made more sense to keep it
separate.

> 
> >
> > This is basically trying to get a prototype written by Richard Fowles
> > written using the tools/perf coding style and libraries.
> >
> > Start it from 'perf sched', this patch starts the process by adding the
> > 'record' subcommand to collect the needed mem loads and stores samples.
> >
> > It also have the basic 'report' skeleton, resolving the sample address
> > and hooking the events found in a perf.data file with methods to handle
> > them, right now just printing the resolved perf_sample data structure
> > after each event name.
> >
> > [dcz: refreshed to latest upstream changes]
> 
> [SNIP]
> > +perf-c2c(1)
> > +===========
> > +
> > +NAME
> > +----
> > +perf-c2c - Shared Data C2C/HITM Analyzer.
> > +
> > +SYNOPSIS
> > +--------
> > +[verse]
> > +'perf c2c' record
> > +
> > +DESCRIPTION
> > +-----------
> > +These are the variants of perf c2c:
> > +
> > +  'perf c2c record <command>' to record the memory accesses of an arbitrary
> > +  workload.
> > +
> > +SEE ALSO
> > +--------
> > +linkperf:perf-record[1], linkperf:perf-mem[1]
> 
> This document is very terse and only memtions the 'record' subcommand -
> also it's not updated throughout the series.  So I'd like to suggest
> adding a separate documentation patch with full/verbose descriptions at
> the end of this series.
> 
> 
> [SNIP]
> > +static int perf_c2c__read_events(struct perf_c2c *c2c)
> > +{
> > +	int err = -1;
> > +	struct perf_session *session;
> > +	struct perf_data_file file = {
> > +			.path = input_name,
> > +			.mode = PERF_DATA_MODE_READ,
> > +	};
> > +	struct perf_evsel *evsel;
> > +
> > +	session = perf_session__new(&file, 0, &c2c->tool);
> > +	if (session == NULL) {
> > +		pr_debug("No memory for session\n");
> > +		goto out;
> > +	}
> > +
> > +	/* setup the evsel handlers for each event type */
> > +	evlist__for_each(session->evlist, evsel) {
> > +		const char *name = perf_evsel__name(evsel);
> > +		unsigned int i;
> > +
> > +		for (i = 0; i < ARRAY_SIZE(handlers); i++) {
> > +			if (!strcmp(name, handlers[i].name))
> > +				evsel->handler = handlers[i].handler;
> > +		}
> > +	}
> > +
> > +	err = perf_session__process_events(session, &c2c->tool);
> > +	if (err)
> > +		pr_err("Failed to process events, error %d", err);
> 
> You may want to add perf_session__delete() here.
> 
> > +
> > +out:
> > +	return err;
> > +}
> 
> 
> [SNIP]
> > +int cmd_c2c(int argc, const char **argv, const char *prefix __maybe_unused)
> > +{
> > +	struct perf_c2c c2c = {
> > +		.tool = {
> > +			.sample		 = perf_c2c__process_sample,
> > +			.comm		 = perf_event__process_comm,
> > +			.exit		 = perf_event__process_exit,
> > +			.fork		 = perf_event__process_fork,
> > +			.lost		 = perf_event__process_lost,
> 
> It seems that it also needs to handle mmap[2] events otherwise it cannot
> find symbols from an address.
> 
> Thanks,
> Namhyung
> 
> 
> > +			.ordered_samples = true,
> > +		},
> > +	};
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