Re: [PATCH v3 00/10] selftests/resctrl: Fixes and improvements focused on Intel platforms

Shuah Khan
2026-03-31T19:13:07Z

On 3/13/26 14:32, Reinette Chatre wrote:
> Changes since v2:
> - v2: https://lore.kernel.org/linux-patches/cover.1772582958.git.reinette.chatre@intel.com/
> - Rebased on top of v7.0-rc3.
> - Split "selftests/resctrl: Improve accuracy of cache occupancy test" into
> changes impacting L3 and L2 respectively. (Ilpo)
> - "long_mask" -> "full_mask", "return_value" -> "measurement", "org_count"
> -> "orig_count". (Ilpo)
> - Use PATH_MAX where appropriate. (Ilpo)
> - Handle errors first to reduce indentation. (Ilpo)
> - Detailed changes in changelogs.
> - No functional changes since v2. Series tested by running 20 iterations of all
> tests on Emerald Rapids, Granite Rapids, Sapphire Rapids, Ice Lake, Sierra
> Forest, and Broadwell.
>
> Changes since v1:
> - v1: https://lore.kernel.org/lkml/cover.1770406608.git.reinette.chatre@intel.com/
> - The new perf interface that resctrl selftests can utilize has been accepted and
> merged into v7.0-rc2. This series can thus now be considered for inclusion.
> For reference,
> commit 6a8a48644c4b ("perf/x86/intel/uncore: Add per-scheduler IMC CAS count events")
> The resctrl selftest changes making use of the new perf interface are backward
> compatible. The selftests do not require a v7.0-rc2 kernel to run but the
> tests can only pass on recent Intel platforms running v7.0-rc2 or later.
> - Combine the two outstanding resctrl selftest submissions into one series
> for easier tracking:
> https://lore.kernel.org/lkml/084e82b5c29d75f16f24af8768d50d39ba0118a5.1769101788.git.reinette.chatre@intel.com/
> https://lore.kernel.org/lkml/cover.1770406608.git.reinette.chatre@intel.com/
> - Fix typo in changelog of "selftests/resctrl: Improve accuracy of cache
> occupancy test": "the data my be in L2" -> "the data may be in L2"
> - Add Zide Chen's RB tags.
>
> Cover letter updated to be accurate wrt perf changes:
>
> The resctrl selftests fail on recent Intel platforms. Intermittent failures
> in the CAT test and permanent failures of MBM and MBA tests on new platforms
> like Sierra Forest and Granite Rapids.
>
> The MBM and MBA resctrl selftests both generate memory traffic and compare the
> memory bandwidth measurements between the iMC PMUs and MBM to determine pass or
> fail. Both these tests are failing on recent platforms like Sierra Forest and
> Granite Rapids that have two events that need to be read and combined
> for a total memory bandwidth count instead of the single event available on
> earlier platforms.
>
> resctrl selftests prefer to obtain event details via sysfs instead of adding
> model specific details on which events to read. Enhancements to perf to expose
> the new event details are available since:
> commit 6a8a48644c4b ("perf/x86/intel/uncore: Add per-scheduler IMC CAS count events")
> This series demonstrates use of the new sysfs interface to perf
> to obtain accurate iMC read memory bandwidth measurements.
>
> An additional issue with all the tests is that these selftests are part
> performance tests and determine pass/fail on performance heuristics selected
> after running the tests on a variety of platforms. When new platforms
> arrive the previous heuristics may cause the tests to fail. These failures are
> not because of an issue with the resctrl subsystem the tests intend to test
> but because of the architectural changes in the new platforms.
>
> Adapt the resctrl tests to not be as sensitive to architectural changes
> while adjusting the remaining heuristics to ensure tests pass on a variety
> of platforms. More details in individual patches.
>
> Tested by running 100 iterations of all tests on Emerald Rapids, Granite
> Rapids, Sapphire Rapids, Ice Lake, Sierra Forest, and Broadwell.
>
> Reinette Chatre (10):
> selftests/resctrl: Improve accuracy of cache occupancy test
> selftests/resctrl: Reduce interference from L2 occupancy during cache
> occupancy test
> selftests/resctrl: Do not store iMC counter value in counter config
> structure
> selftests/resctrl: Prepare for parsing multiple events per iMC
> selftests/resctrl: Support multiple events associated with iMC
> selftests/resctrl: Increase size of buffer used in MBM and MBA tests
> selftests/resctrl: Raise threshold at which MBM and PMU values are
> compared
> selftests/resctrl: Remove requirement on cache miss rate
> selftests/resctrl: Simplify perf usage in CAT test
> selftests/resctrl: Reduce L2 impact on CAT test
>

Let me know if this series is ready to go into Linux 7.1

thanks,
-- Shuah