From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755487AbeDCLXW (ORCPT ); Tue, 3 Apr 2018 07:23:22 -0400 Received: from merlin.infradead.org ([205.233.59.134]:38120 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755121AbeDCLXV (ORCPT ); Tue, 3 Apr 2018 07:23:21 -0400 Date: Tue, 3 Apr 2018 13:23:11 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: Li RongQing , LKML Subject: Re: [PATCH] genirq: only scan the present CPUs Message-ID: <20180403112311.GF4043@hirez.programming.kicks-ass.net> References: <1522647902-11426-1-git-send-email-lirongqing@baidu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.3 (2018-01-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 03, 2018 at 12:25:56PM +0200, Thomas Gleixner wrote: > 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. BIOS is crap, news at 11. I've got boxes like that too. Use possible_cpu=$nr if you're bothered by it -- it's what I do.