linux-kernel - Re: disabled APICs being counted as processors ?

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Message-ID: <20140125153048.GA8536@redhat.com>
Date:	Sat, 25 Jan 2014 10:30:48 -0500
From:	Dave Jones <davej@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	x86@...nel.org, Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: disabled APICs being counted as processors ?

On Sat, Jan 25, 2014 at 08:41:07AM +0100, Ingo Molnar wrote:
 > 
 > * Dave Jones <davej@...hat.com> wrote:
 > 
 > > I have a system with 4 cores (configured with CONFIG_NR_CPUS=4) that shows during boot..
 > > 
 > > [    0.000000] smpboot: 8 Processors exceeds NR_CPUS limit of 4
 > > 
 > > it looks like this is because..
 > > 
 > > [    0.000000] ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled)
 > > [    0.000000] ACPI: LAPIC (acpi_id[0x02] lapic_id[0x02] enabled)
 > > [    0.000000] ACPI: LAPIC (acpi_id[0x03] lapic_id[0x04] enabled)
 > > [    0.000000] ACPI: LAPIC (acpi_id[0x04] lapic_id[0x06] enabled)
 > > [    0.000000] ACPI: LAPIC (acpi_id[0x05] lapic_id[0xff] disabled)
 > > [    0.000000] ACPI: LAPIC (acpi_id[0x06] lapic_id[0xff] disabled)
 > > [    0.000000] ACPI: LAPIC (acpi_id[0x07] lapic_id[0xff] disabled)
 > > [    0.000000] ACPI: LAPIC (acpi_id[0x08] lapic_id[0xff] disabled)
 > > 
 > > Should the CPU counting code be ignoring those disabled APICs ?
 > 
 > Hm, so to the kernel it looks like as if those were 'possible CPUs', 
 > in theory hotpluggable. Not sure what they are - disabled cores in an 
 > 8-core system? Or BIOS reporting crap?
 > 
 > But perhaps the boot message could be improved to say something like:
 > 
 > > [    0.000000] smpboot: 8 possible processors exceeds NR_CPUS limit of 4

It's not possible though. It's an i5-4670T, in a single socket board.
It doesn't even have hyperthreading. http://ark.intel.com/products/75050/Intel-Core-i5-4670T-Processor-6M-Cache-up-to-3_30-GHz

	Dave

 
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