From: Peter Zijlstra <peterz@infradead.org>
To: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
linux-api@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Tejun Heo <tj@kernel.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Paul Turner <pjt@google.com>,
Quentin Perret <quentin.perret@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Juri Lelli <juri.lelli@redhat.com>, Todd Kjos <tkjos@google.com>,
Joel Fernandes <joelaf@google.com>,
Steve Muckle <smuckle@google.com>,
Suren Baghdasaryan <surenb@google.com>
Subject: Re: [PATCH v6 03/16] sched/core: uclamp: Map TASK's clamp values into CPU's clamp buckets
Date: Mon, 21 Jan 2019 16:05:07 +0100 [thread overview]
Message-ID: <20190121150507.GJ27931@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190115101513.2822-4-patrick.bellasi@arm.com>
On Tue, Jan 15, 2019 at 10:15:00AM +0000, Patrick Bellasi wrote:
> +static inline unsigned int uclamp_bucket_value(unsigned int clamp_value)
> +{
> +#define UCLAMP_BUCKET_DELTA (SCHED_CAPACITY_SCALE / CONFIG_UCLAMP_BUCKETS_COUNT)
> +#define UCLAMP_BUCKET_UPPER (UCLAMP_BUCKET_DELTA * CONFIG_UCLAMP_BUCKETS_COUNT)
> +
> + if (clamp_value >= UCLAMP_BUCKET_UPPER)
> + return SCHED_CAPACITY_SCALE;
> +
> + return UCLAMP_BUCKET_DELTA * (clamp_value / UCLAMP_BUCKET_DELTA);
> +}
> +static void uclamp_bucket_inc(struct uclamp_se *uc_se, unsigned int clamp_id,
> + unsigned int clamp_value)
> +{
> + union uclamp_map *uc_maps = &uclamp_maps[clamp_id][0];
> + unsigned int prev_bucket_id = uc_se->bucket_id;
> + union uclamp_map uc_map_old, uc_map_new;
> + unsigned int free_bucket_id;
> + unsigned int bucket_value;
> + unsigned int bucket_id;
> +
> + bucket_value = uclamp_bucket_value(clamp_value);
Aahh!!
So why don't you do:
bucket_id = clamp_value / UCLAMP_BUCKET_DELTA;
bucket_value = bucket_id * UCLAMP_BUCKET_DELTA;
> + do {
> + /* Find the bucket_id of an already mapped clamp bucket... */
> + free_bucket_id = UCLAMP_BUCKETS;
> + for (bucket_id = 0; bucket_id < UCLAMP_BUCKETS; ++bucket_id) {
> + uc_map_old.data = atomic_long_read(&uc_maps[bucket_id].adata);
> + if (free_bucket_id == UCLAMP_BUCKETS && !uc_map_old.se_count)
> + free_bucket_id = bucket_id;
> + if (uc_map_old.value == bucket_value)
> + break;
> + }
> +
> + /* ... or allocate a new clamp bucket */
> + if (bucket_id >= UCLAMP_BUCKETS) {
> + /*
> + * A valid clamp bucket must always be available.
> + * If we cannot find one: refcounting is broken and we
> + * warn once. The sched_entity will be tracked in the
> + * fast-path using its previous clamp bucket, or not
> + * tracked at all if not yet mapped (i.e. it's new).
> + */
> + if (unlikely(free_bucket_id == UCLAMP_BUCKETS)) {
> + SCHED_WARN_ON(free_bucket_id == UCLAMP_BUCKETS);
> + return;
> + }
> + bucket_id = free_bucket_id;
> + uc_map_old.data = atomic_long_read(&uc_maps[bucket_id].adata);
> + }
And then skip all this?
> +
> + uc_map_new.se_count = uc_map_old.se_count + 1;
> + uc_map_new.value = bucket_value;
> +
> + } while (!atomic_long_try_cmpxchg(&uc_maps[bucket_id].adata,
> + &uc_map_old.data, uc_map_new.data));
> +
> + uc_se->value = clamp_value;
> + uc_se->bucket_id = bucket_id;
> +
> + if (uc_se->mapped)
> + uclamp_bucket_dec(clamp_id, prev_bucket_id);
> +
> + /*
> + * Task's sched_entity are refcounted in the fast-path only when they
> + * have got a valid clamp_bucket assigned.
> + */
> + uc_se->mapped = true;
> +}
next prev parent reply other threads:[~2019-01-21 15:05 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-15 10:14 [PATCH v6 00/16] Add utilization clamping support Patrick Bellasi
2019-01-15 10:14 ` [PATCH v6 01/16] sched/core: Allow sched_setattr() to use the current policy Patrick Bellasi
2019-01-25 13:56 ` Alessio Balsini
2019-01-15 10:14 ` [PATCH v6 02/16] sched/core: uclamp: Extend sched_setattr() to support utilization clamping Patrick Bellasi
2019-01-15 10:15 ` [PATCH v6 03/16] sched/core: uclamp: Map TASK's clamp values into CPU's clamp buckets Patrick Bellasi
2019-01-21 10:15 ` Peter Zijlstra
2019-01-21 12:27 ` Patrick Bellasi
2019-01-21 12:51 ` Peter Zijlstra
2019-01-21 15:05 ` Peter Zijlstra [this message]
2019-01-21 15:34 ` Patrick Bellasi
2019-01-15 10:15 ` [PATCH v6 04/16] sched/core: uclamp: Add CPU's clamp buckets refcounting Patrick Bellasi
2019-01-21 14:59 ` Peter Zijlstra
2019-01-21 15:23 ` Patrick Bellasi
2019-01-21 16:12 ` Peter Zijlstra
2019-01-21 16:33 ` Patrick Bellasi
2019-01-22 9:45 ` Peter Zijlstra
2019-01-22 10:31 ` Patrick Bellasi
2019-01-21 15:17 ` Peter Zijlstra
2019-01-21 15:54 ` Patrick Bellasi
2019-01-22 10:03 ` Peter Zijlstra
2019-01-22 10:53 ` Patrick Bellasi
2019-01-15 10:15 ` [PATCH v6 05/16] sched/core: uclamp: Update CPU's refcount on clamp changes Patrick Bellasi
2019-01-21 15:33 ` Peter Zijlstra
2019-01-21 15:44 ` Patrick Bellasi
2019-01-22 9:37 ` Peter Zijlstra
2019-01-22 10:43 ` Patrick Bellasi
2019-01-22 13:28 ` Peter Zijlstra
2019-01-22 14:01 ` Patrick Bellasi
2019-01-22 14:57 ` Peter Zijlstra
2019-01-22 15:33 ` Patrick Bellasi
2019-01-23 9:16 ` Peter Zijlstra
2019-01-23 14:14 ` Patrick Bellasi
2019-01-23 18:59 ` Peter Zijlstra
2019-01-24 11:21 ` Patrick Bellasi
2019-01-24 12:38 ` Peter Zijlstra
2019-01-15 10:15 ` [PATCH v6 06/16] sched/core: uclamp: Enforce last task UCLAMP_MAX Patrick Bellasi
2019-01-15 10:15 ` [PATCH v6 07/16] sched/core: uclamp: Add system default clamps Patrick Bellasi
2019-01-22 13:56 ` Peter Zijlstra
2019-01-22 14:43 ` Patrick Bellasi
2019-01-22 15:13 ` Peter Zijlstra
2019-01-22 15:41 ` Patrick Bellasi
2019-01-23 9:22 ` Peter Zijlstra
2019-01-23 14:19 ` Patrick Bellasi
2019-01-23 19:10 ` Peter Zijlstra
2019-01-15 10:15 ` [PATCH v6 08/16] sched/cpufreq: uclamp: Add utilization clamping for FAIR tasks Patrick Bellasi
2019-01-22 10:37 ` Rafael J. Wysocki
2019-01-22 11:02 ` Patrick Bellasi
2019-01-22 11:04 ` Rafael J. Wysocki
2019-01-22 11:27 ` Patrick Bellasi
2019-01-22 15:21 ` Peter Zijlstra
2019-01-22 15:45 ` Patrick Bellasi
2019-01-22 17:13 ` Peter Zijlstra
2019-01-22 18:18 ` Patrick Bellasi
2019-01-23 9:52 ` Peter Zijlstra
2019-01-23 14:24 ` Patrick Bellasi
2019-01-15 10:15 ` [PATCH v6 09/16] sched/cpufreq: uclamp: Add utilization clamping for RT tasks Patrick Bellasi
2019-01-22 12:30 ` Quentin Perret
2019-01-22 12:37 ` Patrick Bellasi
2019-01-23 10:28 ` Peter Zijlstra
2019-01-23 14:33 ` Patrick Bellasi
2019-01-23 10:49 ` Peter Zijlstra
2019-01-23 14:40 ` Patrick Bellasi
2019-01-23 20:11 ` Peter Zijlstra
2019-01-24 12:30 ` Patrick Bellasi
2019-01-24 12:38 ` Patrick Bellasi
2019-01-24 15:12 ` Peter Zijlstra
2019-01-24 16:00 ` Patrick Bellasi
2019-01-24 15:31 ` Peter Zijlstra
2019-01-24 16:14 ` Patrick Bellasi
2019-01-24 15:33 ` Peter Zijlstra
2019-01-24 15:15 ` Peter Zijlstra
2019-01-24 16:05 ` Patrick Bellasi
2019-01-15 10:15 ` [PATCH v6 10/16] sched/core: Add uclamp_util_with() Patrick Bellasi
2019-01-23 13:33 ` Peter Zijlstra
2019-01-23 14:51 ` Patrick Bellasi
2019-01-23 19:22 ` Peter Zijlstra
2019-01-15 10:15 ` [PATCH v6 11/16] sched/fair: Add uclamp support to energy_compute() Patrick Bellasi
2019-01-22 12:13 ` Quentin Perret
2019-01-22 12:45 ` Patrick Bellasi
2019-01-22 13:29 ` Quentin Perret
2019-01-22 14:26 ` Patrick Bellasi
2019-01-22 14:39 ` Quentin Perret
2019-01-22 15:01 ` Patrick Bellasi
2019-01-22 15:14 ` Quentin Perret
2019-01-15 10:15 ` [PATCH v6 12/16] sched/core: uclamp: Extend CPU's cgroup controller Patrick Bellasi
2019-01-15 10:15 ` [PATCH v6 13/16] sched/core: uclamp: Propagate parent clamps Patrick Bellasi
2019-01-15 10:15 ` [PATCH v6 14/16] sched/core: uclamp: Map TG's clamp values into CPU's clamp buckets Patrick Bellasi
2019-01-15 10:15 ` [PATCH v6 15/16] sched/core: uclamp: Use TG's clamps to restrict TASK's clamps Patrick Bellasi
2019-01-15 10:15 ` [PATCH v6 16/16] sched/core: uclamp: Update CPU's refcount on TG's clamp changes Patrick Bellasi
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