Re: [PATCH 0/5] Intel Code/Data Prioritization(CDP) feature enabling

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 02/09/15 09:27, He Chen wrote:
> Hi all,
>
> Code/Data Prioritization(CDP) is offered in Intel Broadwell and later server
> platforms, which is an extension of CAT. CDP enables isolation and separate
> prioritization of code and data fetches to the L3 cache in a software
> configurable manner, which can enable workload prioritization and tuning of
> cache capacity to the characteristics of the workload. CDP extends Cache
> Allocation Technology (CAT) by providing separate code and data capacity bit
> masks(CBM) per Class of Service (COS). CDP is used on VM basis in the Xen
> implementation.
>
> More information about CDP, please refer to Intel SDM, Volumn 3, section 17.16
> http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-manual-325462.pdf
>
> This patch series enables CDP feature in Xen based on CAT code, including
> extending CBM operation functions and introducing new commands to enable/disable
> CDP dynamically. For all the changes, please see in each patch.
>
> This patchset has been tested on Intel Broadwell server platform.
>
> To make this patchset better, any comment or suggestion is welcomed, I would
> really appreciate it.

I have taken a look at patches 1-3.  For the most part, it looks good.

The main point I have is on patch 2, as to whether it is sensible to
permit enabling/disabling cdp at runtime.  I suggest that it is not
sensible, and should be a command line parameter instead.

If this is agreed as ok going forwards, patches 3 through 5 should
become rather more simple.

~Andrew