linux-kernel - [PATCH 0/3] Fix a couple of corner cases in feec() when using uclamp

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Message-Id: <20230129161444.1674958-1-qyousef@layalina.io>
Date:   Sun, 29 Jan 2023 16:14:41 +0000
From:   Qais Yousef <qyousef@...alina.io>
To:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     linux-kernel@...r.kernel.org, Lukasz Luba <lukasz.luba@....com>,
        Wei Wang <wvw@...gle.com>, Xuewen Yan <xuewen.yan94@...il.com>,
        Hank <han.lin@...iatek.com>,
        Jonathan JMChen <Jonathan.JMChen@...iatek.com>,
        Qais Yousef <qyousef@...alina.io>
Subject: [PATCH 0/3] Fix a couple of corner cases in feec() when using uclamp_max

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 + Vincent's v4 of
Unlink util_fits_cpu()... patch [1]

[1] https://lore.kernel.org/lkml/20230119174244.2059628-1-vincent.guittot@linaro.org/

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 |  4 ++++
 kernel/sched/core.c          |  1 +
 kernel/sched/fair.c          | 23 +++++++++++++++--------
 3 files changed, 20 insertions(+), 8 deletions(-)

-- 
2.25.1