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

From: Robin Murphy
Date: Wed May 01 2019 - 07:02:31 EST

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%

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,

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

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 :/



@@ -348,7 +348,7 @@ void __cpu_die(unsigned int cpu)
pr_crit("CPU%u: cpu didn't die\n", cpu);
- 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.

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