From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Mike Galbraith <mgalbraith@suse.de>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Peter Zijlstra <peterz@infradead.org>,
Linux PM <linux-pm@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <fweisbec@gmail.com>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Thomas Ilsche <thomas.ilsche@tu-dresden.de>,
Doug Smythies <dsmythies@telus.net>,
Rik van Riel <riel@surriel.com>,
Aubrey Li <aubrey.li@linux.intel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC/RFT][PATCH v2 0/6] sched/cpuidle: Idle loop rework
Date: Fri, 9 Mar 2018 10:58:56 +0100 [thread overview]
Message-ID: <CAJZ5v0hWDA7T=xaNZ1uTEDL_BjRj9zeFZY45AhsUAK5FtRovjw@mail.gmail.com> (raw)
In-Reply-To: <1520516417.7807.88.camel@suse.de>
On Thu, Mar 8, 2018 at 2:40 PM, Mike Galbraith <mgalbraith@suse.de> wrote:
> On Thu, 2018-03-08 at 12:10 +0100, Rafael J. Wysocki wrote:
>> On Thu, Mar 8, 2018 at 11:31 AM, Mike Galbraith <mgalbraith@suse.de> wrote:
>> 1 2 3
>> > 4.16.0.g1b88acc-master 6.95 7.03 6.91 (virgin)
>> > 4.16.0.g1b88acc-master 7.20 7.25 7.26 (+v2)
>> > 4.16.0.g1b88acc-master 6.90 7.06 6.95 (+local)
>> >
>> > Why would v2 charge the light firefox load a small but consistent fee?
>>
>> Two effects may come into play here I think.
>>
>> One is that allowing the tick to run biases the menu governor's
>> predictions towards the lower end, so we may use shallow states more
>> as a result then (Peter was talking about that).
>
> Hm, I'd expect that to show up in +local as well then, as it keeps the
> tick running when avg_idle < sched_migration_cost (convenient magic
> number), but the firefox load runs at the same wattage as virgin. I'm
> also doing this...
>
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -335,7 +335,7 @@ static int menu_select(struct cpuidle_dr
> * C1's exit latency exceeds the user configured limit.
> */
> polling_threshold = max_t(unsigned int, 20, s->target_residency);
> - if (data->next_timer_us > polling_threshold &&
> + if (expected_interval > polling_threshold &&
> latency_req > s->exit_latency && !s->disabled &&
> !dev->states_usage[1].disable)
> first_idx = 1;
>
> ...to help out high frequency cross core throughput, but the firefox
> load apparently doesn't tickle that, as significant polling would
> surely show in the wattage.
OK, so the second reason sounds more likely to me.
Anyway, please retest with the v3 I've just posted. The previous
iteration had a rather serious issue that might very well influence
the results (it was using stale values sometimes).
next prev parent reply other threads:[~2018-03-09 9:58 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-06 8:57 [RFC/RFT][PATCH v2 0/6] sched/cpuidle: Idle loop rework Rafael J. Wysocki
2018-03-06 9:02 ` [RFC/RFT][PATCH v2 1/6] time: tick-sched: Reorganize idle tick management code Rafael J. Wysocki
2018-03-07 23:18 ` Frederic Weisbecker
2018-03-08 9:22 ` Rafael J. Wysocki
2018-03-08 15:14 ` Frederic Weisbecker
2018-03-08 16:34 ` Rafael J. Wysocki
2018-03-08 17:00 ` Frederic Weisbecker
2018-03-06 9:02 ` [RFC/RFT][PATCH v2 2/6] sched: idle: Do not stop the tick upfront in the idle loop Rafael J. Wysocki
2018-03-07 23:39 ` Frederic Weisbecker
2018-03-08 9:05 ` Rafael J. Wysocki
2018-03-06 9:03 ` [RFC/RFT][PATCH v2 3/6] sched: idle: Do not stop the tick before cpuidle_idle_call() Rafael J. Wysocki
2018-03-06 9:05 ` [RFC/RFT][PATCH v2 4/6] cpuidle: Return nohz hint from cpuidle_select() Rafael J. Wysocki
2018-03-06 9:28 ` Rafael J. Wysocki
2018-03-06 10:06 ` [Update][RFC/RFT][PATCH " Rafael J. Wysocki
2018-03-06 9:10 ` [RFC/RFT][PATCH v2 5/6] sched: idle: Select idle state before stopping the tick Rafael J. Wysocki
2018-03-06 9:10 ` [RFC/RFT][PATCH v2 6/6] time: tick-sched: Avoid running the same code twice in a row Rafael J. Wysocki
2018-03-08 10:31 ` [RFC/RFT][PATCH v2 0/6] sched/cpuidle: Idle loop rework Mike Galbraith
2018-03-08 11:10 ` Rafael J. Wysocki
2018-03-08 13:40 ` Mike Galbraith
2018-03-09 9:58 ` Rafael J. Wysocki [this message]
2018-03-07 17:04 Doug Smythies
2018-03-07 22:11 ` Rafael J. Wysocki
2018-03-08 1:28 ` Doug Smythies
2018-03-08 15:18 ` Doug Smythies
2018-03-08 16:16 ` Rik van Riel
2018-03-08 16:36 ` Rafael J. Wysocki
2018-03-08 16:37 ` Rafael J. Wysocki
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