Re: [PATCH v11 0/8] x86/resctrl: mba_MBps enhancement

Reinette Chatre
2024-12-09T17:10:26Z

Hi Boris,

On 12/6/24 8:31 AM, Tony Luck wrote:
> Background
> ----------
>
> The resctrl filesystem supports a mount option that allows users to
> specify a memory bandwidth limit in MiB/s for each domain of a CTRL_MON
> group. The underlying implementation uses data collected from the local
> memory bandwidth monitoring event for the CTRL_MON group and all of
> its MON subgroups as input to a feedback loop that adjusts the memory
> bandwidth allocation control percentage up or down to keep the group
> within the limit set by the user.
>
> Problem statement
> -----------------
>
> Hard coding the local memory bandwidth monitoring event has the following
> issues:
>
> 1) Some systems may support total memory bandwidth monitoring but
> not local. The user cannot use this mount option on such systems.
>
> 2) For large workloads that span NUMA domains using local bandwidth
> monitoring will not throttle jobs correctly.
>
> 3) Users may have a mix of large and small workloads and may want to
> use different input events per CTRL_MON group.
>
> Solution
> --------
>
> A) Provide a new user interface to choose which event is used for each
> CTRL_MON group.
>
> B) Allow systems that only support total memory bandwidth monitoring to
> use total bandwidth event.
>
> Changes since v10:
> Link: https://lore.kernel.org/all/20241122235832.27498-1-tony.luck@intel.com/
>
> Patch Change
> ----- ------
>
> 2 s/filesystm/filesystem/
> Reformat block comment above definition of mba_mbps_default_event using
> more of 80 column width
>
> 3 s/Update_mba_bw()/update_mba_bw()
>
> Added Reinette's Reviewed-by tag to parts 2-8

Could you please consider this series for inclusion?

>
> N.B. v6.13-rc1 introduced a locking change in commit f1be1788a32e ("block:
> model freeze & enter queue as lock for supporting lockdep") that throws
> a lockdep splat when mounting the resctrl filesystem (with certain
> CONFIG options).
>
> Proposed patches that fix this are here:
> Link: https://lore.kernel.org/all/20241206111611.978870-2-ming.lei@redhat.com/
> Link: https://lore.kernel.org/all/20241206111611.978870-3-ming.lei@redhat.com/
>
>
This fix has been merged into v6.13-rc2.

Thank you very much.

Reinette