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    SubjectRe: [PATCH v4 6/7] x86/resctrl: Update documentation with Sub-NUMA cluster changes
    On Fri, Aug 11, 2023 at 10:33:18AM -0700, Reinette Chatre wrote:
    > Hi Tony,
    >
    > On 7/22/2023 12:07 PM, Tony Luck wrote:
    > > With Sub-NUMA Cluster mode enabled the scope of monitoring resources is
    > > per-NODE instead of per-L3 cache. Suffixes of directories with "L3" in
    > > their name refer to Sub-NUMA nodes instead of L3 cache ids.
    > >
    > > Signed-off-by: Tony Luck <tony.luck@intel.com>
    > > Reviewed-by: Peter Newman <peternewman@google.com>
    > > ---
    > > Documentation/arch/x86/resctrl.rst | 10 +++++++---
    > > 1 file changed, 7 insertions(+), 3 deletions(-)
    > >
    > > diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
    > > index cb05d90111b4..4d9ddb91751d 100644
    > > --- a/Documentation/arch/x86/resctrl.rst
    > > +++ b/Documentation/arch/x86/resctrl.rst
    > > @@ -345,9 +345,13 @@ When control is enabled all CTRL_MON groups will also contain:
    > > When monitoring is enabled all MON groups will also contain:
    > >
    > > "mon_data":
    > > - This contains a set of files organized by L3 domain and by
    > > - RDT event. E.g. on a system with two L3 domains there will
    > > - be subdirectories "mon_L3_00" and "mon_L3_01". Each of these
    > > + This contains a set of files organized by L3 domain or by NUMA
    > > + node (depending on whether Sub-NUMA Cluster (SNC) mode is disabled
    > > + or enabled respectively) and by RDT event. E.g. on a system with
    > > + SNC mode disabled with two L3 domains there will be subdirectories
    > > + "mon_L3_00" and "mon_L3_01". The numerical suffix refers to the
    > > + L3 cache id. With SNC enabled the directory names are the same,
    > > + but the numerical suffix refers to the node id. Each of these
    > > directories have one file per event (e.g. "llc_occupancy",
    > > "mbm_total_bytes", and "mbm_local_bytes"). In a MON group these
    > > files provide a read out of the current value of the event for
    >
    > I think it would be helpful to add a modified version of the snippet
    > (from previous patch changelog) regarding well-behaved NUMA apps.
    > With the above it may be confusing that a single cache allocation has
    > multiple cache occupancy counters.
    >
    > This also changes the meaning of the numbers in the directory names.
    > The documentation already provides guidance on how to find the cache
    > ID of a logical CPU (see section "Cache IDs"). I think it will be
    > helpful to add a snippet that makes it clear to users how to map
    > a CPU to its node ID.

    Added extra details as suggested.

    >
    > Reinette

    -Tony

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