Re: [PATCH v9 6/9] x86/resctrl: Add "mba_MBps_event" file to ctrl_mon directories

Reinette Chatre
2024-11-20T04:03:55Z

Hi Tony,

On 11/13/24 4:17 PM, Tony Luck wrote:
> The "mba_MBps" mount option provides an alternate method to
> control memory bandwidth. Instead of specifying allowable
> bandwidth as a percentage of maximum possible, the user
> provides a MiB/s limit value.
>
> Historically the limit was enforced by a feedback loop from

"Historically the limit was enforced" no history needed since
this is still the case at the time of this patch.

> the measure local bandwidth to adjust the memory bandwidth
> allocation controls.

I am not sure what is meant by "a feedback loop from the measure
local bandwidth" (that was copy&pasted to next patch).

>
> In preparation to allow the user to pick the memory bandwidth
> monitoring event used as input to the feedback loop, provide
> a file in each ctrl_mon group directory that shows the event

In the documentation the custom is to use CTRL_MON.

> currently in use.

Much better changelog. I think it will help to add a snippet that
mentions the file is only visible to user space if resctrl
was mounted with mba_MBps, and thus only visible when mba_sc is
enabled, and thus reinforcing that this maintains the contract
that rdtgrp->mba_mbps_event is only accessed when mba_sc is enabled.

>
> Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---

Reinette