Re: [PATCH v8 00/25] x86/resctrl : Support AMD Assignable Bandwidth Monitoring Counters (ABMC)

[Reinette Chatre]

Hi Babu,

On 10/9/24 10:39 AM, Babu Moger wrote:
> 
> This series adds the support for Assignable Bandwidth Monitoring Counters
> (ABMC). It is also called QoS RMID Pinning feature
> 
> Series is written such that it is easier to support other assignable
> features supported from different vendors.
> 
> The feature details are documented in the  APM listed below [1].
> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
> Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth
> Monitoring (ABMC). The documentation is available at
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
> 
> The patches are based on top of commit
> 5b0c5f05fb2fe (tip/master) Merge branch into tip/master: 'x86/splitlock'
> 
> # Introduction
> 
> Users can create as many monitor groups as RMIDs supported by the hardware.
> However, bandwidth monitoring feature on AMD system only guarantees that
> RMIDs currently assigned to a processor will be tracked by hardware.
> The counters of any other RMIDs which are no longer being tracked will be
> reset to zero. The MBM event counters return "Unavailable" for the RMIDs
> that are not tracked by hardware. So, there can be only limited number of
> groups that can give guaranteed monitoring numbers. With ever changing
> configurations there is no way to definitely know which of these groups
> are being tracked for certain point of time. Users do not have the option
> to monitor a group or set of groups for certain period of time without
> worrying about RMID being reset in between.

"worrying about RMID being reset in between" -> "worrying about counter being
reset in between"? 

>     
> The ABMC feature provides an option to the user to assign a hardware
> counter to an RMID, event pair and monitor the bandwidth as long as it is
> assigned.  The assigned RMID will be tracked by the hardware until the user
> unassigns it manually. There is no need to worry about counters being reset
> during this period. Additionally, the user can specify a bitmask identifying
> the specific bandwidth types from the given source to track with the counter.
> 
> Without ABMC enabled, monitoring will work in current 'default' mode without
> assignment option.
> 

Reinette