Re: [PATCH] arm64: Demote boot and shutdown messages to pr_debug

[Robin Murphy]

On 01/05/2019 11:47, Mark Rutland wrote:
> On Tue, Apr 30, 2019 at 03:38:31PM -0700, Florian Fainelli wrote:
> > Similar to commits c68b0274fb3cf ("ARM: reduce "Booted secondary
> > processor" message to debug level") and 035e787543de7 ("ARM: 8644/1: Reduce "CPU:
> > shutdown" message to debug level"), demote the secondary_start_kernel()
> > and __cpu_die() messages from info, respectively notice to debug. While
> > we are at it, also do this for cpu_psci_cpu_kill() which is redundant
> > with __cpu_die().
> >
> > This helps improve the amount of possible hotplug cycles by around +50%
> > on ARCH_BRCMSTB.
>
> Could you elaborate on why that matters?

Yeah, in general if you have a slow serial console then removing all the 
prints from the kernel makes lots of things much faster, but that's not 
necessarily a good argument for doing so. If that's a problem that 
really concerns users then I'd have to ask why they aren't using a 
stricter loglevel or a different console to begin with.

> e.g. is this just for testing, or does this matter in some shutdown or
> hibernate scenario?
>
> > Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> > ---
> >   arch/arm64/kernel/psci.c | 2 +-
> >   arch/arm64/kernel/smp.c  | 4 ++--
> >   2 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
> > index 8cdaf25e99cd..a78581046c80 100644
> > --- a/arch/arm64/kernel/psci.c
> > +++ b/arch/arm64/kernel/psci.c
> > @@ -96,7 +96,7 @@ static int cpu_psci_cpu_kill(unsigned int cpu)
> >   	for (i = 0; i < 10; i++) {
> >   		err = psci_ops.affinity_info(cpu_logical_map(cpu), 0);
> >   		if (err == PSCI_0_2_AFFINITY_LEVEL_OFF) {
> > -			pr_info("CPU%d killed.\n", cpu);
> > +			pr_debug("CPU%d killed.\n", cpu);
> >   			return 0;
> >   		}
> >   
> > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> > index 824de7038967..71fd2b5a3f0e 100644
> > --- a/arch/arm64/kernel/smp.c
> > +++ b/arch/arm64/kernel/smp.c
> > @@ -259,7 +259,7 @@ asmlinkage notrace void secondary_start_kernel(void)
> >   	 * the CPU migration code to notice that the CPU is online
> >   	 * before we continue.
> >   	 */
> > -	pr_info("CPU%u: Booted secondary processor 0x%010lx [0x%08x]\n",
> > +	pr_debug("CPU%u: Booted secondary processor 0x%010lx [0x%08x]\n",
> >   					 cpu, (unsigned long)mpidr,
> >   					 read_cpuid_id());
>
> I generally agree that we don't need to be verbose, and demoting these
> to debug is fine, but it's a shame that these won't be accessible in
> defconfig.
>
> I wonder if we should enable DYNAMIC_DEBUG so that we can turn these on
> from the kernel command line, or if we should have something like a
> verbose_hotplug option specifically for these messages.

We've had DYNAMIC_DEBUG=y in defconfig for a while already :/

Robin.

> Thanks,
> Mark.
>
> >   	update_cpu_boot_status(CPU_BOOT_SUCCESS);
> > @@ -348,7 +348,7 @@ void __cpu_die(unsigned int cpu)
> >   		pr_crit("CPU%u: cpu didn't die\n", cpu);
> >   		return;
> >   	}
> > -	pr_notice("CPU%u: shutdown\n", cpu);
> > +	pr_debug("CPU%u: shutdown\n", cpu);
> >   
> >   	/*
> >   	 * Now that the dying CPU is beyond the point of no return w.r.t.
> > --
> > 2.17.1
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel