Re: [Xen-devel] [PATCH v3 01/15] docs: create Memory Bandwidth Allocation (MBA) feature document

[Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>]

On 17-09-19 00:07:36, Jan Beulich wrote:
> >>> Roger Pau Monné <roger.pau@xxxxxxxxxx> 09/18/17 7:21 PM >>>
> >On Tue, Sep 05, 2017 at 05:32:23PM +0800, Yi Sun wrote:
> >> +## Hardware perspective
> >> +
> >> +  MBA defines a range of MSRs to support specifying a delay value (Thrtl) 
> >> per
> >> +  COS, with details below.
> >> +
> >> +  ```
> >> +   +----------------------------+----------------+
> >> +   | MSR (per socket)           |    Address     |
> >> +   +----------------------------+----------------+
> >> +   | IA32_L2_QOS_Ext_BW_Thrtl_0 |     0xD50      |
> >> +   +----------------------------+----------------+
> >> +   | ...                        |  ...           |
> >> +   +----------------------------+----------------+
> >> +   | IA32_L2_QOS_Ext_BW_Thrtl_n |     0xD50+n    |
> >> +   +----------------------------+----------------+
> >> +  ```
> >> +
> >> +  When context switch happens, the COS ID of domain is written to 
> >> per-thread MSR
> >> +  `IA32_PQR_ASSOC`, and then hardware enforces bandwidth allocation 
> >> according
> >
> >I think this is missing some context of the relation between a thread
> >and the MSR. I assume it's related to IA32_PQR_ASSOC, but I have no
> >idea what that constant means.
> >
> >What's more, Xen doesn't have threads, so you should maybe speak about
> >vCPUs instead?
> 
> I think talk is of hardware aspects here, i.e. "thread" as in "hyper-thread".
> 
> Jan
> 
Indeed. Will make it more clear.

> 
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