linux-kernel - Re: [PATCH V2 3/5] perf stat: Support per-die aggregation

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Date:   Tue, 4 Jun 2019 21:55:00 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        ak@...ux.intel.com
Subject: Re: [PATCH V2 3/5] perf stat: Support per-die aggregation

On Mon, Jun 03, 2019 at 01:42:58PM -0400, Liang, Kan wrote:
> 
> 
> On 6/3/2019 12:36 PM, Jiri Olsa wrote:
> > On Thu, May 30, 2019 at 07:53:47AM -0700, kan.liang@...ux.intel.com wrote:
> > 
> > SNIP
> > 
> > > +
> > >   static int perf_env__get_core(struct cpu_map *map, int idx, void *data)
> > >   {
> > >   	struct perf_env *env = data;
> > >   	int core = -1, cpu = perf_env__get_cpu(env, map, idx);
> > >   	if (cpu != -1) {
> > > -		int socket_id = env->cpu[cpu].socket_id;
> > > -
> > >   		/*
> > > -		 * Encode socket in upper 16 bits
> > > -		 * core_id is relative to socket, and
> > > +		 * Encode socket in upper 24 bits
> > 
> > please note we use upper 8 bits for socket number,
> > the comments suggests it's 24 bits
> 
> I will fix it in v3.
> 
> > 
> > > +		 * encode die id in upper 16 bits
> > > +		 * core_id is relative to socket and die,
> > >   		 * we need a global id. So we combine
> > > -		 * socket + core id.
> > > +		 * socket + die id + core id
> > >   		 */
> > > -		core = (socket_id << 16) | (env->cpu[cpu].core_id & 0xffff);
> > > +		if (WARN_ONCE(env->cpu[cpu].socket_id >> 8,
> > > +		    "The socket_id number is too big. Please upgrade the perf tool.\n"))
> > 
> > hum, how's perf tool upgrade going to help in here?
> 
> 
> I think there is nothing we can do for current encoding, if the socket
> number or die number is bigger than 8 bits. We have to design a new encoding
> method, which needs to update the perf tool.
> So I use a similar expression from process_cpu_topology().
> 		if (do_core_id_test && nr != (u32)-1 && nr > (u32)cpu_nr) {
> 			pr_debug("socket_id number is too big."
> 				 "You may need to upgrade the perf tool.\n");
> 			goto free_cpu;
> 		}
> 
> Any suggestions for the warning message?

not really :-\ perhaps the original is more accurate
and does not "claim" the upgrade will help.. it's just
a nit.. feel free to keep it

thanks,
jirka