linux-kernel - Re: [PATCH 13/32] Documentation, x86: Documentation for Intel resource allocation user interface

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Date:	Wed, 27 Jul 2016 11:20:31 -0500
From:	Nilay Vaish <nilayvaish@...il.com>
To:	Fenghua Yu <fenghua.yu@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <h.peter.anvin@...el.com>,
	Tony Luck <tony.luck@...el.com>, Tejun Heo <tj@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Stephane Eranian <eranian@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	David Carrillo-Cisneros <davidcc@...gle.com>,
	Ravi V Shankar <ravi.v.shankar@...el.com>,
	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	Sai Prakhya <sai.praneeth.prakhya@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH 13/32] Documentation, x86: Documentation for Intel
 resource allocation user interface

On 12 July 2016 at 20:02, Fenghua Yu <fenghua.yu@...el.com> wrote:
> +1. Terms
> +========
> +
> +We use the following terms and concepts in this documentation.
> +
> +RDT: Intel Resoure Director Technology
> +
> +CAT: Cache Allocation Technology
> +
> +CDP: Code and Data Prioritization
> +
> +CBM: Cache Bit Mask
> +
> +Cache ID: A cache identification. It is unique in one cache index on the
> +platform. User can find cache ID in cache sysfs interface:
> +/sys/devices/system/cpu/cpu*/cache/index*/id
> +
> +Share resource domain: A few different resources can share same QoS mask
> +MSRs array. For example, one L2 cache can share QoS MSRs with its next level
> +L3 cache. A domain number represents the L2 cache, the L3 cache, the L2
> +cache's shared cpumask, and the L3 cache's shared cpumask.
> +

I think CLOS ID should be defined here.  Is it same as Cache ID?


> +As one example, CAT L3's schema format is:
> +
> +L3:<cache_id0>=<cbm>;<cache_id1>=<cbm>;...
> +
> +On a two socket machine, L3's schema line could be:
> +
> +L3:0=ff;1=c0
> +
> +which means this line in "schemas" file is for CAT L3, L3 cache id 0's CBM
> +is 0xff, and L3 cache id 1's CBM is 0xc0.
> +
> +If one resource is disabled, its line is not shown in schemas file.
> +
> +The schema line can be expended for situations. L3 cbms format can be
> +expended to CDP enabled L3 cbms format:
> +
> +L3:<cache_id0>=<d_cbm>,<i_cbm>;<cache_id1>=<d_cbm>,<i_cbm>;...
> +
> +Initial value is all ones which means all tasks use all resources initially.
> +

Your example here makes me feel that Cache ID and CLOS ID mean the same thing.


> +7. Some usage examples
> +======================
> +
> +7.1 Example 1 for sharing CLOSID on socket 0 between two partitions
> +
> +Only L3 cbm is enabled. Assume the machine is 2-socket and dual-core without
> +hyperthreading.
> +
> +#mount -t rscctrl rscctrl /sys/fs/rscctrl
> +#cd /sys/fs/rscctrl
> +#mkdir p0 p1
> +#echo "L3:0=3;1=c" > /sys/fs/rscctrl/p0/schemas
> +#echo "L3:0=3;1=3" > /sys/fs/rscctrl/p1/schemas
> +
> +In partition p0, kernel allocates CLOSID 0 for L3 cbm=0x3 on socket 0 and
> +CLOSID 0 for cbm=0xc on socket 1.
> +
> +In partition p1, kernel allocates CLOSID 0 for L3 cbm=0x3 on socket 0 and
> +CLOSID 1 for cbm=0x3 on socket 1.


And over here you have switched to using CLOS ID and you do not
mention Cache ID at all.
As I said above, I think Cache ID and CLOS ID are the same thing.  If
that is the case, I think Cache ID should be completely replaced with
CLOS ID.

--
Nilay