Re: [Xen-devel] [PATCH v3 15/15] docs: add MBA description in docs

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

On Tue, Sep 05, 2017 at 05:32:37PM +0800, Yi Sun wrote:
> This patch adds MBA description in related documents.
> 
> Signed-off-by: Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>
> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
> v2:
>     - state the value type shown by 'psr-mba-show'. For linear mode,
>       it shows decimal value. For non-linear mode, it shows hexadecimal
>       value.
>       (suggested by Chao Peng)
> ---
>  docs/man/xl.pod.1.in      | 34 +++++++++++++++++++++++++
>  docs/misc/xl-psr.markdown | 63 
> +++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 97 insertions(+)
> 
> diff --git a/docs/man/xl.pod.1.in b/docs/man/xl.pod.1.in
> index 16c8306..e644b19 100644
> --- a/docs/man/xl.pod.1.in
> +++ b/docs/man/xl.pod.1.in
> @@ -1798,6 +1798,40 @@ processed.
>  
>  =back
>  
> +=head2 Memory Bandwidth Allocation
> +
> +Intel Skylake and later server platforms offer capabilities to configure and
> +make use of the Memory Bandwidth Allocation (MBA) mechanisms, which provides
> +OS/VMMs the ability to slow misbehaving apps/VMs or create advanced 
> closed-loop

I don't get the 'closed-loop' thing again, but that might just be me
since I'm not a native speaker.

> +control system via exposing control over a credit-based throttling mechanism.
> +In the Xen implementation, MBA is used to control memory bandwidth on VM 
> basis.
> +To enforce bandwidth on a specific domain, just set throttling value (THRTL)
> +for the domain.
> +
> +=over 4
> +
> +=item B<psr-mba-set> [I<OPTIONS>] I<domain-id> I<thrtl>
> +
> +Set throttling value (THRTL) for a domain. For how to specify I<thrtl>
> +please refer to L<http://xenbits.xen.org/docs/unstable/misc/xl-psr.html>.
> +
> +B<OPTIONS>
> +
> +=over 4
> +
> +=item B<-s SOCKET>, B<--socket=SOCKET>
> +
> +Specify the socket to process, otherwise all sockets are processed.
> +
> +=back
> +
> +=item B<psr-mba-show> [I<domain-id>]
> +
> +Show MBA settings for a certain domain or all domains. For linear mode, it
> +shows the decimal value. For non-linear mode, it shows hexadecimal value.
> +
> +=back
> +
>  =head1 IGNORED FOR COMPATIBILITY WITH XM
>  
>  xl is mostly command-line compatible with the old xm utility used with
> diff --git a/docs/misc/xl-psr.markdown b/docs/misc/xl-psr.markdown
> index 04dd957..39fc801 100644
> --- a/docs/misc/xl-psr.markdown
> +++ b/docs/misc/xl-psr.markdown
> @@ -186,6 +186,69 @@ Setting data CBM for a domain:
>  Setting the same code and data CBM for a domain:
>  `xl psr-cat-set <domid> <cbm>`
>  
> +## Memory Bandwidth Allocation (MBA)
> +
> +Memory Bandwidth Allocation (MBA) is a new feature available on Intel
> +Skylake and later server platforms that allows an OS or Hypervisor/VMM to
> +slow misbehaving apps/VMs or create advanced closed-loop control system via
> +exposing control over a credit-based throttling mechanism. To enforce 
> bandwidth
> +on a specific domain, just set throttling value (THRTL) into Class of Service
> +(COS). MBA provides two THRTL mode. One is linear mode and the other is
> +non-linear mode.
> +
> +In the linear mode the input precision is defined as 100-(THRTL_MAX). Values
> +not an even multiple of the precision (e.g., 12%) will be rounded down (e.g.,
> +to 10% delay applied).
               ^ s/applied/by the hardware/

Thanks, Roger.

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