linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Ionela Voinescu <ionela.voinescu@arm.com>
To: catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com,
	maz@kernel.org, suzuki.poulose@arm.com, sudeep.holla@arm.com,
	dietmar.eggemann@arm.com, ionela.voinescu@arm.com
Cc: peterz@infradead.org, mingo@redhat.com, ggherdovich@suse.cz,
	vincent.guittot@linaro.org, linux-arm-kernel@lists.infradead.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	Juri Lelli <juri.lelli@redhat.com>
Subject: [PATCH v2 5/6] TEMP: sched: add interface for counter-based frequency invariance
Date: Wed, 18 Dec 2019 18:26:06 +0000	[thread overview]
Message-ID: <20191218182607.21607-6-ionela.voinescu@arm.com> (raw)
In-Reply-To: <20191218182607.21607-1-ionela.voinescu@arm.com>

To be noted that this patch is a temporary one. It introduces the
interface added by the patches at [1] to allow update of the frequency
invariance scale factor based on counters. If [1] is merged there is
not need for this patch.

For platforms that support counters (x86 - APERF/MPERF, arm64 - AMU
counters) the frequency invariance correction factor can be obtained
using a core counter and a fixed counter to get information on the
performance (frequency based only) obtained in a period of time. This
will more accurately reflect the actual current frequency of the CPU,
compared with the alternative implementation that reflects the request
of a performance level from the OS through the cpufreq framework
(arch_set_freq_scale).

Therefore, introduce an interface - arch_scale_freq_tick, to be
implemented by each architecture and called for each CPU on the tick
to update the scale factor based on the delta in the counter values,
if counter support is present on the CPU.

Either because reading counters is expensive or because reading
counters from remote CPUs is not possible or is expensive, only
update the counter based frequency scale factor on the tick for
now. A tick based update will definitely be necessary either due to
it being the only point of update for certain architectures or in
order to cache the counter values for a particular CPU, if a
further update from that CPU is not possible.

[1]
https://lore.kernel.org/lkml/20191113124654.18122-1-ggherdovich@suse.cz/

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Giovanni Gherdovich <ggherdovich@suse.cz>
Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
---
 kernel/sched/core.c  | 1 +
 kernel/sched/sched.h | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 90e4b00ace89..e0b70b9fb5cc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3594,6 +3594,7 @@ void scheduler_tick(void)
 	struct task_struct *curr = rq->curr;
 	struct rq_flags rf;
 
+	arch_scale_freq_tick();
 	sched_clock_tick();
 
 	rq_lock(rq, &rf);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 280a3c735935..afdafcf7f9da 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1771,6 +1771,13 @@ static inline void set_next_task(struct rq *rq, struct task_struct *next)
 	next->sched_class->set_next_task(rq, next, false);
 }
 
+#ifndef arch_scale_freq_tick
+static __always_inline
+void arch_scale_freq_tick(void)
+{
+}
+#endif
+
 #ifdef CONFIG_SMP
 #define sched_class_highest (&stop_sched_class)
 #else
-- 
2.17.1


  parent reply	other threads:[~2019-12-18 18:27 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-18 18:26 [PATCH v2 0/6] arm64: ARMv8.4 Activity Monitors support Ionela Voinescu
2019-12-18 18:26 ` [PATCH v2 1/6] arm64: add support for the AMU extension v1 Ionela Voinescu
2020-01-23 17:04   ` Valentin Schneider
2020-01-23 18:32     ` Ionela Voinescu
2020-01-24 12:00       ` Valentin Schneider
2020-01-28 11:00         ` Ionela Voinescu
2020-01-28 16:34   ` Suzuki Kuruppassery Poulose
2020-01-29 16:42     ` Ionela Voinescu
2019-12-18 18:26 ` [PATCH v2 2/6] arm64: trap to EL1 accesses to AMU counters from EL0 Ionela Voinescu
2020-01-23 17:04   ` Valentin Schneider
2020-01-23 17:34     ` Ionela Voinescu
2019-12-18 18:26 ` [PATCH v2 3/6] arm64/kvm: disable access to AMU registers from kvm guests Ionela Voinescu
2020-01-27 15:33   ` Valentin Schneider
2020-01-28 15:48     ` Ionela Voinescu
2020-01-28 17:26     ` Suzuki Kuruppassery Poulose
2020-01-28 17:37       ` Valentin Schneider
2020-01-28 17:52         ` Ionela Voinescu
2019-12-18 18:26 ` [PATCH v2 4/6] Documentation: arm64: document support for the AMU extension Ionela Voinescu
2020-01-27 16:47   ` Valentin Schneider
2020-01-28 16:53     ` Ionela Voinescu
2020-01-28 18:36       ` Valentin Schneider
2020-01-30 15:04   ` Suzuki Kuruppassery Poulose
2020-01-30 16:45     ` Ionela Voinescu
2020-01-30 18:26       ` Suzuki K Poulose
2020-01-31  9:54         ` Ionela Voinescu
2019-12-18 18:26 ` Ionela Voinescu [this message]
2020-01-29 19:37   ` [PATCH v2 5/6] TEMP: sched: add interface for counter-based frequency invariance Peter Zijlstra
2020-01-30 15:33     ` Ionela Voinescu
2019-12-18 18:26 ` [PATCH v2 6/6] arm64: use activity monitors for " Ionela Voinescu
2020-01-23 11:49   ` Lukasz Luba
2020-01-23 17:07     ` Ionela Voinescu
2020-01-24  1:19       ` Lukasz Luba
2020-01-24 13:12         ` Ionela Voinescu
2020-01-24 15:17           ` Lukasz Luba
2020-01-28 17:36             ` Ionela Voinescu
2020-01-29 17:13   ` Valentin Schneider
2020-01-29 17:52     ` Ionela Voinescu
2020-01-29 23:39     ` Valentin Schneider
2020-01-30 15:49       ` Ionela Voinescu
2020-01-30 16:11         ` Valentin Schneider

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191218182607.21607-6-ionela.voinescu@arm.com \
    --to=ionela.voinescu@arm.com \
    --cc=catalin.marinas@arm.com \
    --cc=dietmar.eggemann@arm.com \
    --cc=ggherdovich@suse.cz \
    --cc=juri.lelli@redhat.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=maz@kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=sudeep.holla@arm.com \
    --cc=suzuki.poulose@arm.com \
    --cc=vincent.guittot@linaro.org \
    --cc=will@kernel.org \
    --subject='Re: [PATCH v2 5/6] TEMP: sched: add interface for counter-based frequency invariance' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).