linux-kernel - Re: [PATCH v2 06/33] Documentation, x86: Documentation for Intel resource allocation user interface

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Date:   Thu, 8 Sep 2016 15:01:20 -0700
From:   Shaohua Li <shli@...com>
To:     Fenghua Yu <fenghua.yu@...el.com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Ingo Molnar <mingo@...e.hu>, Tony Luck <tony.luck@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>, Borislav Petkov <bp@...e.de>,
        Stephane Eranian <eranian@...gle.com>,
        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 v2 06/33] Documentation, x86: Documentation for Intel
 resource allocation user interface

On Thu, Sep 08, 2016 at 02:57:00AM -0700, Fenghua Yu wrote:
> From: Fenghua Yu <fenghua.yu@...el.com>
> 
> The documentation describes user interface of how to allocate resource
> in Intel RDT.
> 
> Please note that the documentation covers generic user interface. Current
> patch set code only implemente CAT L3. CAT L2 code will be sent later.
> 
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> ---
>  Documentation/x86/intel_rdt_ui.txt | 164 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 164 insertions(+)
>  create mode 100644 Documentation/x86/intel_rdt_ui.txt
> 
> diff --git a/Documentation/x86/intel_rdt_ui.txt b/Documentation/x86/intel_rdt_ui.txt
> new file mode 100644
> index 0000000..27de386
> --- /dev/null
> +++ b/Documentation/x86/intel_rdt_ui.txt
> @@ -0,0 +1,164 @@
> +User Interface for Resource Allocation in Intel Resource Director Technology
> +
> +Copyright (C) 2016 Intel Corporation
> +
> +Fenghua Yu <fenghua.yu@...el.com>
> +Tony Luck <tony.luck@...el.com>
> +
> +This feature is enabled by the CONFIG_INTEL_RDT Kconfig and the
> +X86 /proc/cpuinfo flag bits "rdt", "cat_l3" and "cdp_l3".
> +
> +To use the feature mount the file system:
> +
> + # mount -t resctrl resctrl [-o cdp,verbose] /sys/fs/resctrl
> +
> +mount options are:
> +
> +"cdp": Enable code/data prioritization in L3 cache allocations.
> +
> +"verbose": Output more info in the "info" file under info directory
> +	and in dmesg. This is mainly for debug.
> +
> +
> +Resource groups
> +---------------
> +Resource groups are represented as directories in the resctrl file
> +system. The default group is the root directory. Other groups may be
> +created as desired by the system administrator using the "mkdir(1)"
> +command, and removed using "rmdir(1)".
> +
> +There are three files associated with each group:
> +
> +"tasks": A list of tasks that belongs to this group. Tasks can be
> +	added to a group by writing the task ID to the "tasks" file
> +	(which will automatically remove them from the previous
> +	group to which they belonged). New tasks created by fork(2)
> +	and clone(2) are added to the same group as their parent.
> +	If a pid is not in any sub partition, it is in root partition
> +	(i.e. default partition).
Hi Fenghua,

Will you add a 'procs' interface to allow move a process into a group? Using
the 'tasks' interface to move process is inconvenient and has race conditions
(eg, some new threads could be escaped).

Thanks,
Shaohua