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Date: Tue, 26 Mar 2019 16:12:27 +0100 From: "Rafael J. Wysocki" <rafael@...nel.org> To: Leon Romanovsky <leon@...nel.org> Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, x86 <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, linux-pm <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH -next] x86/apic: Reduce print level of CPU limit announcement On Tue, Mar 26, 2019 at 3:41 PM Leon Romanovsky <leon@...nel.org> wrote: > > On Tue, Mar 26, 2019 at 01:29:54PM +0100, Rafael J. Wysocki wrote: > > On Tue, Mar 26, 2019 at 1:02 PM Leon Romanovsky <leon@...nel.org> wrote: > > > > > > From: Leon Romanovsky <leonro@...lanox.com> > > > > > > Kernel is booted with less possible CPUs (possible_cpus kernel boot > > > option) than available CPUs will have prints like this: > > > > > > [ 1.131039] APIC: NR_CPUS/possible_cpus limit of 8 reached. Processor 55/0x1f ignored. > > > [ 1.132228] ACPI: Unable to map lapic to logical cpu number > > > > > > Those warnings are printed for every not-enabled CPU and on the systems > > > with large number of such CPUs, we see a lot of those prints for default > > > print level. > > > > > > Simple conversion of those prints to be in debug level removes them > > > while leaving the option to debug system. > > > > But generally dynamic debug must be enabled in order for pr_debug() > > prints to be visible which is kind of cumbersome to do via the command > > line. > > It is doable and documented pretty well, which is uncommon :) > https://www.kernel.org/doc/html/latest/admin-guide/dynamic-debug-howto.html#debug-messages-during-boot-process I know. That's what I mean by "kind of cumbersome", because you need to know which debug messages to enable upfront. > > > > > Signed-off-by: Leon Romanovsky <leonro@...lanox.com> > > > --- > > > arch/x86/kernel/acpi/boot.c | 2 +- > > > arch/x86/kernel/apic/apic.c | 6 +++--- > > > 2 files changed, 4 insertions(+), 4 deletions(-) > > > > > > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c > > > index 8dcbf6890714..3ef8ab89c02d 100644 > > > --- a/arch/x86/kernel/acpi/boot.c > > > +++ b/arch/x86/kernel/acpi/boot.c > > > @@ -770,7 +770,7 @@ int acpi_map_cpu(acpi_handle handle, phys_cpuid_t physid, u32 acpi_id, > > > > > > cpu = acpi_register_lapic(physid, acpi_id, ACPI_MADT_ENABLED); > > > if (cpu < 0) { > > > - pr_info(PREFIX "Unable to map lapic to logical cpu number\n"); > > > + pr_debug(PREFIX "Unable to map lapic to logical cpu number\n"); > > > > And this one is printed sometimes when something really goes wrong > > which may be really hard to debug otherwise, so there is value in the > > info level here. > > > > Would it be possible to avoid printing it just in some cases? > > This can do the trick: > > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c > index 3ef8ab89c02d..00212b3991e0 100644 > --- a/arch/x86/kernel/acpi/boot.c > +++ b/arch/x86/kernel/acpi/boot.c > @@ -770,7 +770,10 @@ int acpi_map_cpu(acpi_handle handle, phys_cpuid_t physid, u32 acpi_id, > > cpu = acpi_register_lapic(physid, acpi_id, ACPI_MADT_ENABLED); > if (cpu < 0) { > - pr_debug(PREFIX "Unable to map lapic to logical cpu number\n"); > + if (cpu == -ENOENT) > + pr_debug(PREFIX "Unable to map lapic to logical cpu number\n"); I don't think it is necessary to print this in the -ENOENT case, as there is a message for that case that will be printed anyway. > + else > + pr_info(PREFIX "Unable to map lapic to logical cpu number\n"); > return cpu; > } >
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