Date: Thu, 3 Jul 2014 11:51:35 +0200
From: Borislav Petkov <bp@alien8.de>
To: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org,
        toshi.kani@hp.com, imammedo@redhat.com, huawei.libin@huawei.com,
        paul.gortmaker@windriver.com, linux-kernel@vger.kernel.org,
        srivatsa.bhat@linux.vnet.ibm.com
Subject: Re: [PATCH] x86,cpu-hotplug: clear llc_shared_mask at CPU hotplug
Message-ID: <20140703095135.GA21776@pd.tnic>
References: <53B3A991.2070502@jp.fujitsu.com>
 <20140702113253.GD1318@pd.tnic>
 <53B4E1A4.2050502@jp.fujitsu.com>
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On Thu, Jul 03, 2014 at 01:52:52PM +0900, Yasuaki Ishimatsu wrote:
> I think that the reason to apply CPU number to ACPI ID is that CPU is
> used for the application without considering physical CPU. So even if
> CPU number is changed, it is no matter.

I don't think I understand what you're saying here...

> Thus the readded cores is numbered to unused CPU number.

Well, maybe we should use some method to number cores in a stable manner
so that they don't get new numbers when they reappear.

> I think the mask has 2 meanings as follows:
>   - representing CPUs that share same CPU cache.

... that share the last level cache.

>   - representing onlined CPUs

no, for that we have cpu_online_mask.

> So even if we keep their old numbers, we should clear the mask when
> offlinig CPU.

No, cpu_online_mask is for onlined cores. I think the mask which shows
which cores share a last level cache should not be changed *IF* the core
numbers remain stable, that is.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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