Re: [PATCH v2 1/3] powerpc/numa: Print debug statements only when required

[Michael Ellerman <mpe@ellerman.id.au>]

Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
> * Laurent Dufour <ldufour@linux.ibm.com> [2021-08-23 11:21:33]:
>> Le 21/08/2021 à 12:25, Srikar Dronamraju a écrit :
>> > Currently, a debug message gets printed every time an attempt to
>> > add(remove) a CPU. However this is redundant if the CPU is already added
>> > (removed) from the node.
>> > 
>> > Cc: linuxppc-dev@lists.ozlabs.org
>> > Cc: Nathan Lynch <nathanl@linux.ibm.com>
>> > Cc: Michael Ellerman <mpe@ellerman.id.au>
>> > Cc: Ingo Molnar <mingo@kernel.org>
>> > Cc: Peter Zijlstra <peterz@infradead.org>
>> > Cc: Valentin Schneider <valentin.schneider@arm.com>
>> > Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
>> > Cc: Vincent Guittot <vincent.guittot@linaro.org>
>> > Cc: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>
>> > Cc: Laurent Dufour <ldufour@linux.ibm.com>
>> > Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
>> > ---
>> >   arch/powerpc/mm/numa.c | 11 +++++------
>> >   1 file changed, 5 insertions(+), 6 deletions(-)
>> > 
>> > diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
>> > index f2bf98bdcea2..fbe03f6840e0 100644
>> > --- a/arch/powerpc/mm/numa.c
>> > +++ b/arch/powerpc/mm/numa.c
>> > @@ -141,10 +141,11 @@ static void map_cpu_to_node(int cpu, int node)
>> >   {
>> >   	update_numa_cpu_lookup_table(cpu, node);
>> > -	dbg("adding cpu %d to node %d\n", cpu, node);
>> > -	if (!(cpumask_test_cpu(cpu, node_to_cpumask_map[node])))
>> > +	if (!(cpumask_test_cpu(cpu, node_to_cpumask_map[node]))) {
>> > +		dbg("adding cpu %d to node %d\n", cpu, node);
>> >   		cpumask_set_cpu(cpu, node_to_cpumask_map[node]);
>> > +	}
>> >   }
>> >   #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PPC_SPLPAR)
>> > @@ -152,13 +153,11 @@ static void unmap_cpu_from_node(unsigned long cpu)
>> >   {
>> >   	int node = numa_cpu_lookup_table[cpu];
>> > -	dbg("removing cpu %lu from node %d\n", cpu, node);
>> > -
>> >   	if (cpumask_test_cpu(cpu, node_to_cpumask_map[node])) {
>> >   		cpumask_clear_cpu(cpu, node_to_cpumask_map[node]);
>> > +		dbg("removing cpu %lu from node %d\n", cpu, node);
>> >   	} else {
>> > -		printk(KERN_ERR "WARNING: cpu %lu not found in node %d\n",
>> > -		       cpu, node);
>> > +		pr_err("WARNING: cpu %lu not found in node %d\n", cpu, node);
>> 
>> Would pr_warn() be more appropriate here (or removing the "WARNING" statement)?
>
> Its a fair point.
>
> Michael,
>
> Do you want me to resend this patch with s/pr_err/pr_warn for the above
> line?

I think what I'd prefer is if we stopped using this custom dbg() stuff
in numa.c, and cleaned up all the messages to use pr_xxx().

Those debug statements only appear if you boot with numa=debug, which is
not documented anywhere and I had completely forgotten existed TBH.

These days there's CONFIG_DYNAMIC_DEBUG for turning on/off messages,
which is much more flexible.

So can we drop the numa=debug bits, and convert all the dbg()s to
pr_debug().

And then do a pass converting all the printk("NUMA: ") to pr_xxx() which
will get "numa:" from pr_fmt().

cheers