linux-kernel - Re: [PATCH v12 20/26] x86/resctrl: Provide interface to update the event configurations

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Message-ID: <fda6c46d-c01c-494f-a2ba-efbcb1f331b4@intel.com>
Date: Wed, 16 Apr 2025 11:52:50 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: <babu.moger@....com>, <tony.luck@...el.com>, <peternewman@...gle.com>
CC: <corbet@....net>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<bp@...en8.de>, <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
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Subject: Re: [PATCH v12 20/26] x86/resctrl: Provide interface to update the
 event configurations

Hi Babu,

On 4/15/25 1:37 PM, Moger, Babu wrote:
> Hi Reinette,
> 
> On 4/11/25 17:07, Reinette Chatre wrote:
>> Hi Babu,
>>
>> On 4/3/25 5:18 PM, Babu Moger wrote:
>>> Users can modify the event configuration by writing to the event_filter
>>> interface file. The event configurations for mbm_cntr_assign mode are
>>> located in /sys/fs/resctrl/info/event_configs/.
>>>
>>> Update the assignments of all groups when the event configuration is
>>> modified.
>>>
>>> Example:
>>> $ cd /sys/fs/resctrl/
>>> $ echo "local_reads, local_non_temporal_writes" >
>>>   info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>>>
>>> $ cat info/L3_MON/counter_configs/mbm_total_bytes/event_filter
>>>  local_reads, local_non_temporal_writes
>>>
>>> Signed-off-by: Babu Moger <babu.moger@....com>
>>> ---
>>> v12: New patch to modify event configurations.
>>> ---
>>>  Documentation/arch/x86/resctrl.rst     |  10 +++
>>>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 115 ++++++++++++++++++++++++-
>>>  2 files changed, 124 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
>>> index 99f9f4b9b501..4e6feba6fb08 100644
>>> --- a/Documentation/arch/x86/resctrl.rst
>>> +++ b/Documentation/arch/x86/resctrl.rst
>>> @@ -335,6 +335,16 @@ with the following files:
>>>  	    # cat /sys/fs/resctrl/info/L3_MON/counter_configs/mbm_local_bytes/event_filter
>>>  	    local_reads, local_non_temporal_writes, local_reads_slow_memory
>>>  
>>> +	The event configuration can be modified by writing to the event_filter file within
>>> +	the configuration directory.
>>
>> Please use imperative tone.
> 
> Sure.
> 
> Basic question - Should the user doc also be in imperative mode? I thought
> it only applies to commit log.

I am not aware of a documented rule that user doc should be in imperative mode. I
requested imperative tone here because writing in this way helps to remove ambiguity
and fits with how the rest of the resctrl files are described.

Looking at this specific addition I realized that there is no initial description of
what "event_filter" contains and to make things more confusing the term "event" is
used for both the individual "events" being counted (remote_reads, local_reads, etc.) as
well as the (what will eventually be dynamic) name for collection of "events" being counted,
mbm_total_bytes and mbm_local_bytes. 

Since "event" have been used for mbm_total_bytes and mbm_local_bytes since beginning we
should try to come up with term that can describe what they are configured with.

Below is a start of trying to address this but I think more refinement is needed (other
possible terms for "transactions" could perhaps be "data sources"? ... what do you think?):

	"The read/write event_filter file contains the configuration of the event
	 that reflects which transactions(?) are being counted by it."

Reinette