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

[Shuah Khan]

On 3/13/26 14:32, Reinette Chatre wrote:
> Changes since v2:
> - v2: https://lore.kernel.org/linux-patches/cover.1772582958.git.reinette.chatre@xxxxxxxxx/
> - 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@xxxxxxxxx/
> - 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@xxxxxxxxx/
>    https://lore.kernel.org/lkml/cover.1770406608.git.reinette.chatre@xxxxxxxxx/
> - 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