linux-kernel - [PATCH v16 0/9] Add support for Sub-NUMA cluster (SNC) systems

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Message-ID: <20240312214247.91772-1-tony.luck@intel.com>
Date: Tue, 12 Mar 2024 14:42:38 -0700
From: Tony Luck <tony.luck@...el.com>
To: Fenghua Yu <fenghua.yu@...el.com>,
	Reinette Chatre <reinette.chatre@...el.com>,
	Peter Newman <peternewman@...gle.com>,
	Jonathan Corbet <corbet@....net>,
	Shuah Khan <skhan@...uxfoundation.org>,
	x86@...nel.org
Cc: Shaopeng Tan <tan.shaopeng@...itsu.com>,
	James Morse <james.morse@....com>,
	Jamie Iles <quic_jiles@...cinc.com>,
	Babu Moger <babu.moger@....com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Drew Fustini <dfustini@...libre.com>,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	patches@...ts.linux.dev,
	Tony Luck <tony.luck@...el.com>
Subject: [PATCH v16 0/9] Add support for Sub-NUMA cluster (SNC) systems

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 CPU support an MSR that can partition the RMID counters in
the same way. This allows monitoring features to be used. With the caveat
that users must be aware that Linux may migrate tasks more frequently
between SNC nodes than between "regular" NUMA nodes, so reading counters
from all SNC nodes may be needed to get a complete picture of activity
for tasks.

Cache and memory bandwidth allocation features continue to operate at
the scope of the L3 cache.

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

---
Changes since v15: Link: https://lore.kernel.org/all/20240228112935.8087-tony.luck@intel.com/

0) Note that v14 Reviewed/Testing tags have been removed because of the
   extent of refactoring to catch up with upstream. But nothing
   fundamental changed, so everything should look familiar.

1) Refactor to apply on top of Link: https://lore.kernel.org/all/20240308213846.77075-1-tony.luck@intel.com/
   [So base commit is either tip x86/cache, or upstream current merge PLUS
    the two patches in that series]

2) Add patch 9 which adds files showing mappings from domains to CPUs
   Reinette suggested this, James thinks it duplicates information
   that can be gathered from /sys/devices/system/
   Discussion here: Link: https://lore.kernel.org/all/ZetcM9GO2PH6SC0j@agluck-desk3/
   This part is a nice-to-have. I'm fine if just the first eight patches
   are applied without this while the discussion continues.

Tony Luck (9):
  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: Sub NUMA Cluster detection and enable
  x86/resctrl: Update documentation with Sub-NUMA cluster changes
  x86/resctrl: Add info files to show mappings from domains to lists of
    cpus

 Documentation/arch/x86/resctrl.rst        |  44 ++-
 include/linux/resctrl.h                   |  85 +++--
 arch/x86/include/asm/msr-index.h          |   1 +
 arch/x86/kernel/cpu/resctrl/internal.h    |  67 ++--
 arch/x86/kernel/cpu/resctrl/core.c        | 428 ++++++++++++++++++----
 arch/x86/kernel/cpu/resctrl/ctrlmondata.c |  56 +--
 arch/x86/kernel/cpu/resctrl/monitor.c     |  70 ++--
 arch/x86/kernel/cpu/resctrl/pseudo_lock.c |  26 +-
 arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 213 +++++++----
 9 files changed, 718 insertions(+), 272 deletions(-)

-- 
2.44.0