linux-kernel - Re: [PATCH 2/2] show nohz

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Message-ID: <20150328180608.GA15175@lerouge>
Date:	Sat, 28 Mar 2015 19:06:10 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Li Zefan <lizefan@...wei.com>,
	Tejun Heo <tj@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 2/2] show nohz_full cpus in sysfs

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  <riel@...hat.com>:
> >> From: Rik van Riel <riel@...hat.com>
> >>
> >> 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 :-)
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