linux-kernel - Re: [PATCH] perf: fix topology test on systems with sparse CPUs

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Date:   Mon, 30 Jan 2017 14:29:08 -0500 (EST)
From:   Jan Stancek <jstancek@...hat.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...hat.com, acme@...nel.org,
        alexander shishkin <alexander.shishkin@...ux.intel.com>,
        jolsa@...nel.org, mhiramat@...nel.org,
        rui teng <rui.teng@...ux.vnet.ibm.com>,
        sukadev@...ux.vnet.ibm.com
Subject: Re: [PATCH] perf: fix topology test on systems with sparse CPUs





----- Original Message -----
> From: "Jiri Olsa" <jolsa@...hat.com>
> To: "Jan Stancek" <jstancek@...hat.com>
> Cc: linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...hat.com, acme@...nel.org, "alexander shishkin"
> <alexander.shishkin@...ux.intel.com>, jolsa@...nel.org, mhiramat@...nel.org, "rui teng"
> <rui.teng@...ux.vnet.ibm.com>, sukadev@...ux.vnet.ibm.com
> Sent: Monday, 30 January, 2017 7:49:08 PM
> Subject: Re: [PATCH] perf: fix topology test on systems with sparse CPUs
> 
> On Mon, Jan 30, 2017 at 05:53:34PM +0100, Jan Stancek wrote:
> 
> SNIP
> 
> > +		ret = build_cpu_topo(tp, cpu);
> >  		if (ret < 0)
> >  			break;
> >  	}
> > +
> > +out_free:
> > +	cpu_map__put(map);
> >  	if (ret) {
> >  		free_cpu_topo(tp);
> >  		tp = NULL;
> >  	}
> > +out:
> >  	return tp;
> >  }
> >  
> > @@ -575,7 +579,7 @@ static int write_cpu_topology(int fd, struct
> > perf_header *h __maybe_unused,
> >  	if (ret < 0)
> >  		goto done;
> >  
> > -	for (j = 0; j < perf_env.nr_cpus_avail; j++) {
> > +	for (j = 0; j < perf_env.nr_cpus_online; j++) {
> 
> so basically we're changing from avail to online cpus
> 
> have you checked all the users of this FEATURE
> if such change is ok?

You're right, I missed some. Looking again, I see at least
perf_env__get_core() could break.

Regards,
Jan