From: Valentin Schneider <valentin.schneider@arm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>
Subject: Re: [PATCH v3 9/9] sched/topology: Define and use shortcut pointers for wakeup sd_flag scan
Date: Thu, 16 Apr 2020 11:24:20 +0100 [thread overview]
Message-ID: <jhj4ktjpw2z.mognet@arm.com> (raw)
In-Reply-To: <CAKfTPtBDGzrvG=YhjBZBEgfx5EtM-rTC-dWX5phqh4bOY5XqgA@mail.gmail.com>
On 16/04/20 08:46, Vincent Guittot wrote:
>> @@ -6657,7 +6646,19 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
>>
>> rcu_read_lock();
>>
>> - sd = highest_flag_domain(cpu, sd_flag);
>> + switch (wake_flags & (WF_TTWU | WF_FORK | WF_EXEC)) {
>> + case WF_TTWU:
>> + sd_flag = SD_BALANCE_WAKE;
>> + sd = rcu_dereference(per_cpu(sd_balance_wake, cpu));
>
> It's worth having a direct pointer for the fast path which we always
> try to keep short but the other paths are already slow and will not
> get any benefit of this per cpu pointer.
> We should keep the loop for the slow paths
>
Which fast/slow paths are you referring to here? want_affine vs
!want_affine? If so, do you then mean that we should do the switch case
only when !want_affine, and otherwise look for the domain via the
for_each_domain() loop?
>> + break;
>> + case WF_FORK:
>> + sd_flag = SD_BALANCE_FORK;
>> + sd = rcu_dereference(per_cpu(sd_balance_fork, cpu));
>> + break;
>> + default:
>> + sd_flag = SD_BALANCE_EXEC;
>> + sd = rcu_dereference(per_cpu(sd_balance_exec, cpu));
>> + }
>>
>> /*
>> * If !want_affine, we just look for the highest domain where
next prev parent reply other threads:[~2020-04-16 11:46 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 21:05 [PATCH v3 0/9] sched: Streamline select_task_rq() & select_task_rq_fair() Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 1/9] sched/fair: find_idlest_group(): Remove unused sd_flag parameter Valentin Schneider
2020-04-16 7:40 ` Vincent Guittot
2020-05-01 18:22 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 2/9] sched/debug: Make sd->flags sysctl read-only Valentin Schneider
2020-05-01 18:22 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 3/9] sched: Remove checks against SD_LOAD_BALANCE Valentin Schneider
2020-05-01 18:22 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 4/9] sched/topology: Kill SD_LOAD_BALANCE Valentin Schneider
2020-05-01 18:22 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 5/9] sched: Add WF_TTWU, WF_EXEC wakeup flags Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 6/9] sched: Kill select_task_rq()'s sd_flag parameter Valentin Schneider
2020-04-16 7:42 ` Vincent Guittot
2020-04-16 10:24 ` Valentin Schneider
2020-04-16 10:47 ` Peter Zijlstra
2020-04-16 11:43 ` Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 7/9] sched/fair: Dissociate wakeup decisions from SD flag value Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 8/9] sched/fair: Split select_task_rq_fair want_affine logic Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 9/9] sched/topology: Define and use shortcut pointers for wakeup sd_flag scan Valentin Schneider
2020-04-16 7:46 ` Vincent Guittot
2020-04-16 10:24 ` Valentin Schneider [this message]
2020-04-16 13:04 ` Dietmar Eggemann
2020-04-16 13:36 ` Vincent Guittot
2020-04-16 15:27 ` Valentin Schneider
2020-04-16 15:58 ` Vincent Guittot
2020-04-16 20:54 ` Valentin Schneider
2020-04-16 10:58 ` [PATCH v3 0/9] sched: Streamline select_task_rq() & select_task_rq_fair() Peter Zijlstra
2020-04-16 11:00 ` Peter Zijlstra
2020-04-16 11:02 ` Valentin Schneider
2020-04-16 13:00 ` Vincent Guittot
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