[PATCH v20 00/18] Add support for Sub-NUMA cluster (SNC) systems

Tony Luck
2024-06-10T18:35:40Z

This series based on top of tip x86/cache commit f385f0246394
("x86/resctrl: Replace open coded cacheinfo searches")

The Sub-NUMA cluster feature on some Intel processors partitions the CPUs
that share an L3 cache into two or more sets. This plays havoc with the
Resource Director Technology (RDT) monitoring features. Prior to this
patch Intel has advised that SNC and RDT are incompatible.

Some of these CPUs support an MSR that can partition the RMID counters
in the same way. This allows monitoring features to be used. Legacy
monitoring files provide the sum of counters from each SNC node for
backwards compatibility. Additional files per SNC node provide details
per node.

Memory bandwidth allocation features continue to operate at
the scope of the L3 cache.

L3 cache occupancy and allocation operate on the portion of
L3 cache available for each SNC node.

Signed-off-by: Tony Luck <tony.luck@intel.com>

---
Changes since v19: https://lore.kernel.org/all/20240528222006.58283-1-tony.luck@intel.com/

1-4: Refactor on top of <linux/cacheinfo.h> change.
Nothing functional.

5: No change

6: Updated commit message with note about RMID Sharing mode.
Renamed __rmid_read() to __rmid_read_phys() and performed
translation from logical RMID to physical RMID at callsites.
Updated comment for __rmid_read_phys() with explanation of
logical/physical RMIDs. Consistently use "SNC node" avoid
SNC domain. Add specifics for non-SNC mode.
Joined split line on __rmid_read() definition (even with the
added "_phys" to its name still fits on one line.

7: No change

8: get_cpu_cacheinfo_level() moved to <linux/cacheinfo.h>
currently in tip x86/cache
no other changes

9: Dropped the "sumdomains" field from struct rmid_read (a NULL
domain field now indicates that summing is needed).
Fix kerneldoc comments for struct rmid_read.
Updated commit comments with more "why" than "what".

10: No change

11: Fix commit comments per suggestions
1) Added some "why it is OK to take a bit from evtid"
2) s/The stolen bit is given to/Give the bit to/
3) Don't use "l3_cache_id" (which looks like a variable)

12: Fix commit message.
s/kernfs_find_and_get_ns()/kernfs_find_and_get()/
Add kernfs_put() to drop hold from kernfs_find_and_get()
Drop useless "/* create the directory */" comment.

13: Add kernfs_put() to drop hold from kernfs_find_and_get() [two places]

14: Add cpumask parameter to mon_event_read() so SNC decsions are
all in rdtgroup_mondata_show() instead of spread between functions.
Add comments in rdtgroup_mondata_show() to explain the sum vs. no-sum
cases.
Moved the mon_event_read() call into both arms of the if-else
instead of "d = NULL; goto got_cacheinfo;"

15: New (replaces 15-17). Make __mon_event_read() do the sum across
domains (at filesystem level). Move the CPU/domain sanity check out
of resctrl_arch_rmid_read() and into __mon_event_read()
with separate scope tests for single domain vs. sum over
domains.

16: [Was 18] Update commit message with details about MSR 0xCA0, what changes
when bit 0 is cleared, and why this is necessary.
Dropped "Add an architecture specific hook" language from
commit message.

17: [Was 19] Drop "and enabling" from shortlog (enabling done by
previous commit).
Added checks that cpumask_weight() isn't returning zero (to keep
static checkers from warning of possible divide by zero).

18: [Was 20] Fix some "Sub-NUMA" references to say "Sub-NUMA Cluster"
Added document section on effect of SNC mode on MBA and L3 CAT.

Tony Luck (18):
x86/resctrl: Prepare for new domain scope
x86/resctrl: Prepare to split rdt_domain structure
x86/resctrl: Prepare for different scope for control/monitor
operations
x86/resctrl: Split the rdt_domain and rdt_hw_domain structures
x86/resctrl: Add node-scope to the options for feature scope
x86/resctrl: Introduce snc_nodes_per_l3_cache
x86/resctrl: Block use of mba_MBps mount option on Sub-NUMA Cluster
(SNC) systems
x86/resctrl: Prepare for new Sub-NUMA Cluster (SNC) monitor files
x86/resctrl: Add a new field to struct rmid_read for summation of
domains
x86/resctrl: Refactor mkdir_mondata_subdir() with a helper function
x86/resctrl: Allocate a new field in union mon_data_bits
x86/resctrl: Create Sub-NUMA Cluster (SNC) monitor files
x86/resctrl: Handle removing directories in Sub-NUMA Cluster (SNC)
mode
x86/resctrl: Fill out rmid_read structure for smp_call*() to read a
counter
x86/resctrl: Make __mon_event_count() handle sum domains
x86/resctrl: Enable RMID shared RMID mode on Sub-NUMA Cluster (SNC)
systems
x86/resctrl: Sub-NUMA Cluster (SNC) detection
x86/resctrl: Update documentation with Sub-NUMA cluster changes

Documentation/arch/x86/resctrl.rst | 27 ++
include/linux/resctrl.h | 87 ++++--
arch/x86/include/asm/msr-index.h | 1 +
arch/x86/kernel/cpu/resctrl/internal.h | 93 +++++--
arch/x86/kernel/cpu/resctrl/core.c | 312 ++++++++++++++++------
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 85 +++---
arch/x86/kernel/cpu/resctrl/monitor.c | 242 ++++++++++++++---
arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 27 +-
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 272 ++++++++++++-------
9 files changed, 835 insertions(+), 311 deletions(-)

base-commit: f385f024639431bec3e70c33cdbc9563894b3ee5
--
2.45.0