Messages in this thread | | | From | Qais Yousef <> | Subject | [PATCH v4 0/3] Fix a couple of corner cases in feec() when using uclamp_max | Date | Mon, 21 Aug 2023 23:45:01 +0100 |
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Changes in v4:
* Added Reviewed-by Vincent Guittot. * Updated sched_compute_energy_tp() to include max_util and busy_time as requested by Lukasz.
Changes in v3:
* Fix sign comparison problem in patch 1 (Thanks Vincent!) * Simplify comparison and remove function in patch 2 (Thanks Dietmar!)
Changes in v2:
* Use long instead of unsigned long to keep the comparison simple in spite of being inconsistent with how capacity type. * Fix missing termination parenthesis that caused build error. * Rebase on latest tip/sched/core and Vincent v5 of Unlink misift patch.
v1 link: https://lore.kernel.org/lkml/20230129161444.1674958-1-qyousef@layalina.io/ v2 link: https://lore.kernel.org/lkml/20230205224318.2035646-1-qyousef@layalina.io/ v3 link: https://lore.kernel.org/lkml/20230717215717.309174-1-qyousef@layalina.io/
In v2 Dietmar has raised concerns about limitation in current EM calculations that can end up packing more tasks on a cluster. While this is not ideal situation and we need to fix it, but it is another independent problem that is not introduced by this fix. I don't see a reason why we should couple them rather than work on each problem independently. The packing behavior in practice is actually not bad as if something is capped really hard, there's a desire to keep them on this less performant clusters.
Patch 1 addresses a bug because forcing a task on a small CPU to honour uclamp_max hint means we can end up with spare_capacity = 0; but the logic is constructed such that spare_capacity = 0 leads to ignoring this CPU as a candidate to compute_energy().
Patch 2 addresses a bug due to an optimization in feec() that could lead to ignoring tasks whose uclamp_max = 0 but task_util(0) != 0.
Patch 3 adds a new tracepoint in compute_energy() as it was helpful in debugging these two problems.
This is based on tip/sched/core.
Qais Yousef (3): sched/uclamp: Set max_spare_cap_cpu even if max_spare_cap is 0 sched/uclamp: Ignore (util == 0) optimization in feec() when p_util_max = 0 sched/tp: Add new tracepoint to track compute energy computation
include/trace/events/sched.h | 5 +++++ kernel/sched/core.c | 1 + kernel/sched/fair.c | 36 ++++++++++++------------------------ 3 files changed, 18 insertions(+), 24 deletions(-)
-- 2.34.1
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