linux-kernel - Re: [PATCH v3 2/2] perf/bench/numa: Handle discontiguous/sparse numa nodes

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Message-ID: <20171031152657.GU7045@kernel.org>
Date:   Tue, 31 Oct 2017 12:26:57 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     sathnaga@...ux.vnet.ibm.com, mingo@...nel.org,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        srikar@...ux.vnet.ibm.com, bala24@...ux.vnet.ibm.com
Subject: Re: [PATCH v3 2/2] perf/bench/numa: Handle discontiguous/sparse numa
 nodes

Em Tue, Oct 31, 2017 at 08:46:58PM +0530, Naveen N. Rao escreveu:
> On 2017/08/21 10:17AM, sathnaga@...ux.vnet.ibm.com wrote:
> > From: Satheesh Rajendran <sathnaga@...ux.vnet.ibm.com>
> > 
> > Certain systems are designed to have sparse/discontiguous nodes.
> > On such systems, perf bench numa hangs, shows wrong number of nodes
> > and shows values for non-existent nodes. Handle this by only
> > taking nodes that are exposed by kernel to userspace.
> > 
> > Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> > Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> > Signed-off-by: Satheesh Rajendran <sathnaga@...ux.vnet.ibm.com>
> > Signed-off-by: Balamuruhan S <bala24@...ux.vnet.ibm.com>
> > ---
> >  tools/perf/bench/numa.c | 17 ++++++++++-------
> >  1 file changed, 10 insertions(+), 7 deletions(-)
> > 
> > diff --git a/tools/perf/bench/numa.c b/tools/perf/bench/numa.c
> > index 2483174..d4cccc4 100644
> > --- a/tools/perf/bench/numa.c
> > +++ b/tools/perf/bench/numa.c
> > @@ -287,12 +287,12 @@ static cpu_set_t bind_to_cpu(int target_cpu)
> > 
> >  static cpu_set_t bind_to_node(int target_node)
> >  {
> > -	int cpus_per_node = g->p.nr_cpus/g->p.nr_nodes;
> > +	int cpus_per_node = g->p.nr_cpus/nr_numa_nodes();
> >  	cpu_set_t orig_mask, mask;
> >  	int cpu;
> >  	int ret;
> > 
> > -	BUG_ON(cpus_per_node*g->p.nr_nodes != g->p.nr_cpus);
> > +	BUG_ON(cpus_per_node*nr_numa_nodes() != g->p.nr_cpus);
> >  	BUG_ON(!cpus_per_node);
> > 
> >  	ret = sched_getaffinity(0, sizeof(orig_mask), &orig_mask);
> > @@ -692,7 +692,7 @@ static int parse_setup_node_list(void)
> >  			int i;
> > 
> >  			for (i = 0; i < mul; i++) {
> > -				if (t >= g->p.nr_tasks) {
> > +				if (t >= g->p.nr_tasks || !node_has_cpus(bind_node)) {
> >  					printf("\n# NOTE: ignoring bind NODEs starting at NODE#%d\n", bind_node);
> >  					goto out;
> >  				}
> > @@ -973,6 +973,7 @@ static void calc_convergence(double runtime_ns_max, double *convergence)
> >  	int node;
> >  	int cpu;
> >  	int t;
> > +	int processes;
> > 
> >  	if (!g->p.show_convergence && !g->p.measure_convergence)
> >  		return;
> > @@ -1007,13 +1008,14 @@ static void calc_convergence(double runtime_ns_max, double *convergence)
> >  	sum = 0;
> > 
> >  	for (node = 0; node < g->p.nr_nodes; node++) {
> > +		if (!is_node_present(node))
> > +			continue;
> >  		nr = nodes[node];
> >  		nr_min = min(nr, nr_min);
> >  		nr_max = max(nr, nr_max);
> >  		sum += nr;
> >  	}
> >  	BUG_ON(nr_min > nr_max);
> > -
> 
> Looks like an un-necessary change there.

Right, and I would leave the 'int processes' declaration where it is, as
it is not used outside that loop.

The move of that declaration to the top of the calc_convergence()
function made me spend some cycles trying to figure out why that was
done, only to realize that it was an unnecessary change :-\
 
> - Naveen
> 
> >  	BUG_ON(sum > g->p.nr_tasks);
> > 
> >  	if (0 && (sum < g->p.nr_tasks))
> > @@ -1027,8 +1029,9 @@ static void calc_convergence(double runtime_ns_max, double *convergence)
> >  	process_groups = 0;
> > 
> >  	for (node = 0; node < g->p.nr_nodes; node++) {
> > -		int processes = count_node_processes(node);
> > -
> > +		if (!is_node_present(node))
> > +			continue;
> > +		processes = count_node_processes(node);
> >  		nr = nodes[node];
> >  		tprintf(" %2d/%-2d", nr, processes);
> > 
> > @@ -1334,7 +1337,7 @@ static void print_summary(void)
> > 
> >  	printf("\n ###\n");
> >  	printf(" # %d %s will execute (on %d nodes, %d CPUs):\n",
> > -		g->p.nr_tasks, g->p.nr_tasks == 1 ? "task" : "tasks", g->p.nr_nodes, g->p.nr_cpus);
> > +		g->p.nr_tasks, g->p.nr_tasks == 1 ? "task" : "tasks", nr_numa_nodes(), g->p.nr_cpus);
> >  	printf(" #      %5dx %5ldMB global  shared mem operations\n",
> >  			g->p.nr_loops, g->p.bytes_global/1024/1024);
> >  	printf(" #      %5dx %5ldMB process shared mem operations\n",