Re: [Xen-devel] [PATCH v5 01/16] docs: create Memory Bandwidth Allocation (MBA) feature document

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Sat, Sep 30, 2017 at 01:39:11AM +0000, Yi Sun wrote:
> This patch creates MBA feature document in doc/features/. It describes
> key points to implement MBA which is described in details in Intel SDM
> "Introduction to Memory Bandwidth Allocation".
> 
> Signed-off-by: Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Some nits below.

> +## Implementation Description
> +
> +* Hypervisor interfaces:
> +
> +  1. Boot line param: "psr=mba" to enable the feature.
> +
> +  2. SYSCTL:
> +          - XEN_SYSCTL_PSR_MBA_get_info: Get system MBA information.
> +
> +  3. DOMCTL:
> +          - XEN_DOMCTL_PSR_MBA_OP_GET_THRTL: Get throttling for a domain.
> +          - XEN_DOMCTL_PSR_MBA_OP_SET_THRTL: Set throttling for a domain.
> +
> +* xl interfaces:
> +
> +  1. psr-mba-show [domain-id]
> +          Show system/domain runtime MBA throttling value. For linear mode,
> +          it shows the decimal value. For non-linear mode, it shows 
> hexadecimal
> +          value.
> +          => XEN_SYSCTL_PSR_MBA_get_info/XEN_DOMCTL_PSR_MBA_OP_GET_THRTL
> +
> +  2. psr-mba-set [OPTIONS] <domain-id> <throttling>
> +          Set bandwidth throttling for a domain.
> +          => XEN_DOMCTL_PSR_MBA_OP_SET_THRTL
> +
> +  3. psr-hwinfo
> +          Show PSR HW information, including L3 CAT/CDP/L2 CAT/MBA.
> +          => XEN_SYSCTL_PSR_MBA_get_info
> +
> +* Key data structure:
> +
> +  1. Feature HW info
> +
> +     ```
> +     struct {
> +         unsigned int thrtl_max;
> +         bool linear;
> +     } mba;
> +
> +     - Member `thrtl_max`
> +
> +       `thrtl_max` is the max throttling value to be set, i.e. MBA_MAX.
> +
> +     - Member `linear`
> +
> +       `linear` means the response of delay value is linear or not.
> +
> +     As mentioned above, MBA is a member of Intel PSR features, it would

s/would// and s/share/shares/.

> +     share the base PSR infrastructure in Xen. For example, the 'cos_max'
> +     is a common HW property for all features. So, for other data structure
> +     details, please refer to 'intel_psr_cat_cdp.pandoc'.
> +
> +# Limitations
> +
> +MBA can only work on HW which supports it (check by CPUID).

s/by//.

> +
> +# Testing
> +
> +We can execute these commands to verify MBA on different HWs supporting them.
> +
> +For example:
> +  1. User can get the MBA hardware info through 'psr-hwinfo' command. From
> +     result, user can know if this hardware works under linear mode or non-
> +     linear mode, the max throttling value (MBA_MAX) and so on.
> +
> +    root@:~$ xl psr-hwinfo --mba
> +    Memory Bandwidth Allocation (MBA):
> +    Socket ID       : 0
> +    Linear Mode     : Enabled
> +    Maximum COS     : 7
> +    Maximum Throttling Value: 90
> +    Default Throttling Value: 0
> +
> +  2. Then, user can set a throttling value to a domain. For example, set 
> '0xa',

s/0xa/10/

Thanks, Roger.

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