linux-kernel - Re: [PATCH] genirq: only scan the present CPUs

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Date:   Tue, 3 Apr 2018 12:25:56 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Li RongQing <lirongqing@...du.com>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] genirq: only scan the present CPUs

On Mon, 2 Apr 2018, Li RongQing wrote:

> lots of application will read /proc/stat, like ps and vmstat, but we
> find the reading time are spreading on Purley platform which has lots
> of possible CPUs and interrupt.
> 
> To reduce the reading time, only scan the present CPUs, not all possible
> CPUs, which speeds the reading of /proc/stat 20 times on Purley platform
> which has 56 present CPUs, and 224 possible CPUs

Why is BIOS/ACPI telling the kernel that there are 224 possible CPUs unless
it supports physical CPU hotplug.

Thanks,

	tglx