This bug is awaiting verification that the linux/6.2.0-27.28 kernel in
-proposed solves the problem. Please test the kernel and update this bug
with the results. If the problem is solved, change the tag
'verification-needed-lunar' to 'verification-done-lunar'. If the problem
still exists, change the tag 'verification-needed-lunar' to
'verification-failed-lunar'.

If verification is not done by 5 working days from today, this fix will
be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
to enable and use -proposed. Thank you!


** Tags added: kernel-spammed-lunar-linux verification-needed-lunar

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https://bugs.launchpad.net/bugs/2008745

Title:
  [SRU] Intel Sapphire Rapids HBM support needs CONFIG_NUMA_EMU

Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Jammy:
  Fix Committed
Status in linux source package in Kinetic:
  Won't Fix
Status in linux source package in Lunar:
  Fix Committed

Bug description:
  [Impact]

  Currently Ubuntu kernel has this kernel config disabled.
  But in some cases, Intel's Sapphire Rapids High Bandwith
  Memory (SPR-HBM) needs this option.

  Memory bandwidth has been a bottleneck of increasingly memory bound
  workloads. Sapphire Rapids plus HBM is specifically targeted to
  cater to these workloads, traditionally served using overprovisioning
  of memory devices.

  Please search the keyword "fake numa" in
  https://community.intel.com/t5/Blogs/Products-and-
  Solutions/HPC/Enabling-High-Bandwidth-Memory-for-HPC-and-AI-
  Applications-for/post/1335100

  [Fix]

  Enable CONFIG_NUMA_EMU in our kernel config for 5.15 and later

  [Test Plan]
   Use "STREAM-triadd" algorithm* in Intel MLC** to benchmark 3 scenarios (no 
fake NUMA, 2U fake NUMA and 4U fake NUMA).

  * 
https://www.intel.com/content/www/us/en/developer/articles/technical/optimizing-memory-bandwidth-on-stream-triad.html
  ** 
https://www.intel.com/content/www/us/en/download/736633/intel-memory-latency-checker-intel-mlc.html

  An improvement to performance on a Sapphire Rapids CPU with HBM should
  be observed

  [Where problems could occur]

  The regression risk is low

  [Other Info]
  Jammy
  
https://code.launchpad.net/~mreed8855/ubuntu/+source/linux/+git/jammy/+ref/lp_2008745_config_numa_emu_2

  Kinetic
  
https://code.launchpad.net/~mreed8855/ubuntu/+source/linux/+git/kinetic/+ref/lp_2008745_config_numa_emu_kinetic

  Lunar
  
https://code.launchpad.net/~mreed8855/ubuntu/+source/linux/+git/lunar/+ref/config_numa_emu_lunar_2

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