linux-kernel - Re: [RFC PATCH 2/3] net: Replace for_each_possible_cpu with for_each_online

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Date:	Mon, 08 Aug 2016 10:59:08 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	hejianet@...il.com
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	kaber@...sh.net
Subject: Re: [RFC PATCH 2/3] net: Replace for_each_possible_cpu with
 for_each_online_cpu

From: Jia He <hejianet@...il.com>
Date: Mon,  8 Aug 2016 18:22:21 +0800

> In PowerPC server with large number cpus, the loop index in smt=1 could be 
> reduced to 1/8 compared with smt=8.
> Thus cache misses can be reduced.

You can't do this, if cpus go down we still want to report the statistics
they collected while they were up.

So we must use the possible cpu list here.