(AArch64) NR_CPUS limit

[Tyler Baker]

Hi Jon,

On 4 February 2015 at 12:23, Jon Masters <jcm at redhat.com> wrote:
> Hi Folks,
>
> We're currently patching our kernels with a (much) higher maximum for
> NR_CPUS. There are some very large ARM systems coming soon - any
> objections to increasing this to something like 1024 or 4096?

FWIW, I have a few ARMv7 systems complaining about this issue as well.

[    0.000000] WARNING: CPU: 0 PID: 0 at
../arch/arm/kernel/devtree.c:144 arm_dt_init_cpu_maps+0x118/0x1e8()
[    0.000000] DT /cpu 9 nodes greater than max cores 8, capping them
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted
3.19.0-rc7-00032-g5ee0e962603e #1
[    0.000000] Hardware name: Hisilicon HiP04 (Flattened Device Tree)
[    0.000000] [<c0215d94>] (unwind_backtrace) from [<c021165c>]
(show_stack+0x10/0x14)
[    0.000000] [<c021165c>] (show_stack) from [<c091841c>]
(dump_stack+0x78/0x94)
[    0.000000] [<c091841c>] (dump_stack) from [<c0247bc8>]
(warn_slowpath_common+0x74/0xb0)
[    0.000000] [<c0247bc8>] (warn_slowpath_common) from [<c0247c98>]
(warn_slowpath_fmt+0x30/0x40)
[    0.000000] [<c0247c98>] (warn_slowpath_fmt) from [<c0c624b4>]
(arm_dt_init_cpu_maps+0x118/0x1e8)
[    0.000000] [<c0c624b4>] (arm_dt_init_cpu_maps) from [<c0c613a8>]
(setup_arch+0x714/0xa98)
[    0.000000] [<c0c613a8>] (setup_arch) from [<c0c5e940>]
(start_kernel+0x94/0x3d4)
[    0.000000] [<c0c5e940>] (start_kernel) from [<10208084>] (0x10208084)
[    0.000000] ---[ end trace cb88537fdc8fa200 ]---

Is there an advantage (other than convenience) to increasing this
default, then say using the nr_cpu[1] kernel parameter?

>
> (If not I'll send Catalin the trivial patch)
>
> Jon.
>
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> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Cheers,

Tyler

[1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/kernel-parameters.txt#n2473