linux-kernel - Re: [PATCH v5 13/18] x86/intel_rdt: Add mkdir to resctrl file system

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Date:   Fri, 28 Oct 2016 20:41:56 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Fenghua Yu <fenghua.yu@...el.com>
cc:     "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Ingo Molnar <mingo@...e.hu>, Tony Luck <tony.luck@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>,
        Borislav Petkov <bp@...e.de>,
        Dave Hansen <dave.hansen@...el.com>,
        Nilay Vaish <nilayvaish@...il.com>, Shaohua Li <shli@...com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Sai Prakhya <sai.praneeth.prakhya@...el.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v5 13/18] x86/intel_rdt: Add mkdir to resctrl file
 system

On Fri, 28 Oct 2016, Fenghua Yu wrote:
> On Wed, Oct 26, 2016 at 05:01:32PM +0200, Thomas Gleixner wrote:
> > Handles all cases without 'CDP is special' and whatever nonsense intel will
> > come up with in future. All you need to do is to add that force_min_closid
> > field into the resource struct and set it for l3data and l3code.
> > 
> > relaxed_max_closid is set at mount time by an appropriate mount option.
> 
> Can we just do a simple implementation that finds the minimal closid? We
> can implement the maximum closid and mount parameter later?

Sure. I'm a great fan of: Keep It Simple
 
> AFAIK, the minimal closid works in all current situations (L3, L3DATA,
> L3CODE, and L2) and there is no platform that needs to use max closid yet.

Good.
 
> This is the updated patch that only change is to use minimal closid in
> closid_init(). Does it look good?
> 
> +static void closid_init(void)
> +{
> +	struct rdt_resource *r;
> +	int rdt_min_closid;
> +
> +	/* Compute rdt_min_closid across all resources */
> +	rdt_min_closid = 0;
> +	for_each_enabled_rdt_resource(r)
> +		rdt_min_closid = min(rdt_min_closid, r->num_closid);

The result will be 0 :) You want to init rdt_min_closid to 32 or INT_MAX;

Other than that it's perfect !

Thanks,

	tglx