linux-kernel - Re: sched/debug: CPU hotplug operation suffers in a large cpu systems

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Message-ID: <Y2pKh3H0Ukvmfuco@kroah.com>
Date:   Tue, 8 Nov 2022 13:24:39 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Vishal Chourasia <vishalc@...ux.vnet.ibm.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, mingo@...hat.com,
        vincent.guittot@...aro.org, vschneid@...hat.com,
        srikar@...ux.vnet.ibm.com, sshegde@...ux.ibm.com,
        linuxppc-dev@...ts.ozlabs.org, ritesh.list@...il.com,
        aneesh.kumar@...ux.ibm.com
Subject: Re: sched/debug: CPU hotplug operation suffers in a large cpu systems

On Tue, Nov 08, 2022 at 03:30:46PM +0530, Vishal Chourasia wrote:
> 
> Thanks Greg & Peter for your direction. 
> 
> While we pursue the idea of having debugfs based on kernfs, we thought about
> having a boot time parameter which would disable creating and updating of the
> sched_domain debugfs files and this would also be useful even when the kernfs
> solution kicks in, as users who may not care about these debugfs files would
> benefit from a faster CPU hotplug operation.

Ick, no, you would be adding a new user/kernel api that you will be
required to support for the next 20+ years.  Just to get over a
short-term issue before you solve the problem properly.

If you really do not want these debugfs files, just disable debugfs from
your system.  That should be a better short-term solution, right?

Or better yet, disable SCHED_DEBUG, why can't you do that?

thanks,

greg k-h