Re: [PATCH v10 13/13] Documentation/x86: Update resctrl.rst for new features

[Reinette Chatre]

Hi Babu,

On 12/22/2022 3:31 PM, Babu Moger wrote:
> Update the documentation for the new features:
> 1. Slow Memory Bandwidth allocation (SMBA).
>    With this feature, the QOS  enforcement policies can be applied
>    to the external slow memory connected to the host. QOS enforcement
>    is accomplished by assigning a Class Of Service (COS) to a processor
>    and specifying allocations or limits for that COS for each resource
>    to be allocated.
> 
> 2. Bandwidth Monitoring Event Configuration (BMEC).
>    The bandwidth monitoring events mbm_total_bytes and mbm_local_bytes
>    are set to count all the total and local reads/writes respectively.
>    With the introduction of slow memory, the two counters are not
>    enough to count all the different types of memory events. With the
>    feature BMEC, the users have the option to configure mbm_total_bytes
>    and mbm_local_bytes to count the specific type of events.
> 
> Also add configuration instructions with examples.
> 
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---
>  Documentation/x86/resctrl.rst | 141 +++++++++++++++++++++++++++++++++-
>  1 file changed, 139 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/x86/resctrl.rst b/Documentation/x86/resctrl.rst
> index 71a531061e4e..bea6cab06873 100644
> --- a/Documentation/x86/resctrl.rst
> +++ b/Documentation/x86/resctrl.rst
> @@ -17,14 +17,16 @@ AMD refers to this feature as AMD Platform Quality of Service(AMD QoS).
>  This feature is enabled by the CONFIG_X86_CPU_RESCTRL and the x86 /proc/cpuinfo
>  flag bits:
>  
> -=============================================	================================
> +===============================================	================================
>  RDT (Resource Director Technology) Allocation	"rdt_a"
>  CAT (Cache Allocation Technology)		"cat_l3", "cat_l2"
>  CDP (Code and Data Prioritization)		"cdp_l3", "cdp_l2"
>  CQM (Cache QoS Monitoring)			"cqm_llc", "cqm_occup_llc"
>  MBM (Memory Bandwidth Monitoring)		"cqm_mbm_total", "cqm_mbm_local"
>  MBA (Memory Bandwidth Allocation)		"mba"
> -=============================================	================================
> +SMBA (Slow Memory Bandwidth Allocation)         "smba"
> +BMEC (Bandwidth Monitoring Event Configuration) "bmec"
> +===============================================	================================
>  
>  To use the feature mount the file system::
>  
> @@ -161,6 +163,82 @@ with the following files:
>  "mon_features":
>  		Lists the monitoring events if
>  		monitoring is enabled for the resource.
> +		Example::
> +
> +			# cat /sys/fs/resctrl/info/L3_MON/mon_features
> +			llc_occupancy
> +			mbm_total_bytes
> +			mbm_local_bytes
> +
> +		If the system supports Bandwidth Monitoring Event
> +		Configuration (BMEC), then the bandwidth events will
> +		be configurable. The output will be::
> +
> +			# cat /sys/fs/resctrl/info/L3_MON/mon_features
> +			llc_occupancy
> +			mbm_total_bytes
> +			mbm_total_bytes_config
> +			mbm_local_bytes
> +			mbm_local_bytes_config
> +
> +"mbm_total_bytes_config", "mbm_local_bytes_config":
> +	Read/write files containing the configuration for the mbm_total_bytes
> +	and mbm_local_bytes events, respectively, when the Bandwidth
> +	Monitoring Event Configuration (BMEC) feature is supported.
> +	The event configuration settings are domain specific and affect
> +	all the CPUs in the domain. When an event configuration is changed,
> +	the bandwidth counters for all the RMIDs and the events will be
> +	cleared for that domain. The next read for every RMID will report

I think it needs to be emphasized that configuring one event impacts
all events. How about (please feel free to change): "When either event
configuration is changed, the bandwidth counters for all RMIDs of both
events (mbm_total_bytes as well as mbm_local_bytes) are cleared for that
domain. The next read ..."

> +	"Unavailable" and subsequent reads will report the valid value.
> +


Reinette