From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752330AbbC1SGQ (ORCPT ); Sat, 28 Mar 2015 14:06:16 -0400 Received: from mail-wi0-f177.google.com ([209.85.212.177]:34840 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752191AbbC1SGO (ORCPT ); Sat, 28 Mar 2015 14:06:14 -0400 Date: Sat, 28 Mar 2015 19:06:10 +0100 From: Frederic Weisbecker To: Rik van Riel Cc: LKML , Li Zefan , Tejun Heo , Greg Kroah-Hartman Subject: Re: [PATCH 2/2] show nohz_full cpus in sysfs Message-ID: <20150328180608.GA15175@lerouge> References: <1427493027-15955-1-git-send-email-riel@redhat.com> <1427493027-15955-3-git-send-email-riel@redhat.com> <5516D3BC.6030704@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5516D3BC.6030704@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Mar 28, 2015 at 12:15:56PM -0400, Rik van Riel wrote: > On 03/28/2015 12:02 PM, Frederic Weisbecker wrote: > > 2015-03-27 22:50 GMT+01:00 : > >> From: Rik van Riel > >> > >> Currently there is no way to query which CPUs are in nohz_full > >> mode from userspace. > > > > Well you can watch dmesg | grep NO_HZ > > But surely sysfs is more convenient from an app. > > > > I guess it's ok, as long as it's strictly Read Only. Here it seems to > > be the case. And it's not chmod'able, right? > > I followed the other code for files in that directory. > > Quick testing shows that the cpu info files in > /sys/devices/system/cpu are chmoddable, but writing > to them fails with -EIO because there is no function > set up to handle writes. So yeah, read only :) Perfect :-)