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? > > e.g. is this just for testing, or does this matter in some shutdown or > hibernate scenario? > >> Signed-off-by: Florian Fainelli <f.faine...@gmail.com> >> --- >> 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.
I really wonder what kind of workload is hotplug-happy enough that these two messages become a bottleneck. Why isn't turning down the loglevel enough? Thanks, M. -- Jazz is not dead. It just smells funny...