Re: [PATCH v11 07/23] x86/resctrl: Introduce the interface to display monitor mode

[Moger, Babu]

Hi Reinette,

On 2/6/2025 12:01 PM, Reinette Chatre wrote:
> Hi Babu,
>
> On 1/22/25 12:20 PM, Babu Moger wrote:
> > Introduce the interface file "mbm_assign_mode" to list monitor modes
> > supported.
> >
> > The "mbm_cntr_assign" mode provides the option to assign a counter to
> > an RMID, event pair and monitor the bandwidth as long as it is assigned.
> >
> > On AMD systems "mbm_cntr_assign" is backed by the ABMC (Assignable
>
> ""mbm_cntr_assign" is backed" -> ""mbm_cntr_assign" mode is backed"?

Sure.
> > Bandwidth Monitoring Counters) hardware feature and is enabled by default.
> >
> > The "default" mode is the existing monitoring mode that works without the
> > explicit counter assignment, instead relying on dynamic counter assignment
> > by hardware that may result in hardware not dedicating a counter resulting
> > in monitoring data reads returning "Unavailable".
> >
> > Provide an interface to display the monitor mode on the system.
> > $ cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
> > [mbm_cntr_assign]
> > default
> >
> > Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> > ---
>
>
> > ---
> >   Documentation/arch/x86/resctrl.rst     | 26 +++++++++++++++++++++
> >   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 31 ++++++++++++++++++++++++++
> >   2 files changed, 57 insertions(+)
> >
> > diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> > index fb90f08e564e..b5defc5bce0e 100644
> > --- a/Documentation/arch/x86/resctrl.rst
> > +++ b/Documentation/arch/x86/resctrl.rst
> > @@ -257,6 +257,32 @@ with the following files:
> >   	    # cat /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config
> >   	    0=0x30;1=0x30;3=0x15;4=0x15
> >   
> > +"mbm_assign_mode":
> > +	Reports the list of monitoring modes supported. The enclosed brackets
> > +	indicate which mode is enabled.
> > +	::
> > +
> > +	  # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
> > +	  [mbm_cntr_assign]
> > +	  default
> > +
> > +	"mbm_cntr_assign":
> > +
> > +	In mbm_cntr_assign, monitoring event can only accumulate data while
>
> "In mbm_cntr_assign, monitoring event" -> "In mbm_cntr_assign mode, a monitoring event"?

Sure.

> > +	it is backed by a hardware counter. The user-space is able to specify
> > +	which of the events in CTRL_MON or MON groups should have a counter
> > +	assigned using the "mbm_assign_control" file. The number of counters
> > +	available is described in the "num_mbm_cntrs" file. Changing the mode
> > +	may cause all counters on a resource to reset.
> > +
> > +	"default":
> > +
> > +	In default mode, resctrl assumes there is a hardware counter for each
> > +	event within every CTRL_MON and MON group. On AMD platforms, it is
> > +	recommended to use mbm_cntr_assign mode if supported, because reading
> > +	"mbm_total_bytes" or "mbm_local_bytes" will report 'Unavailable' if
>
> Reinette

Thanks
Babu