From: Uladzislau Rezki <urezki@gmail.com>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
Joel Fernandes <joel@joelfernandes.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
LKML <linux-kernel@vger.kernel.org>,
Rushikesh S Kadam <rushikesh.s.kadam@intel.com>,
"Uladzislau Rezki (Sony)" <urezki@gmail.com>,
Neeraj upadhyay <neeraj.iitr10@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>, rcu <rcu@vger.kernel.org>,
Vineeth Pillai <vineeth@bitbyteword.org>
Subject: Re: [PATCH v4 00/14] Implement call_rcu_lazy() and miscellaneous fixes
Date: Tue, 30 Aug 2022 18:44:51 +0200 [thread overview]
Message-ID: <Yw4+g/0yEf7fpHrh@pc636> (raw)
In-Reply-To: <20220830162244.GA73392@lothringen>
Hello, Frederic.
>
> Although who knows, may be some periodic file operation while idle are specific
> to Android. I'll try to trace lazy callbacks while idle and the number of grace
> periods associated.
>
>
Everything related to lazy call-backs is about not waking "nocb"
kthreads in order to offload one or i should say few callbacks
because it is more or less useless. Currently if incoming callback
is the only one, it will kick a GP whereas a GP will kick nocb_kthread
to offload.
In "light" loaded test cases, especially where a power drain is a key
thing, such light load may lead to some kind of "noise" produced by the
RCU core, i.e. kicking idle CPUs, thus wasting power. On our ARM devices
it is not painful, but there is a small power gain and it is visible.
For other systems, like Joel measures for Intel SoC it is more visible,
because of a power cost getting in/out of isle states.
This is what i see on my setup.
--
Uladzislau Rezki
next prev parent reply other threads:[~2022-08-30 16:45 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-19 20:48 [PATCH v4 00/14] Implement call_rcu_lazy() and miscellaneous fixes Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 01/14] rcu: Introduce call_rcu_lazy() API implementation Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 02/14] rcu: shrinker for lazy rcu Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 03/14] rcuscale: Add laziness and kfree tests Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 04/14] fs: Move call_rcu() to call_rcu_lazy() in some paths Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 05/14] rcutorture: Add test code for call_rcu_lazy() Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 06/14] debug: Toggle lazy at runtime and change flush jiffies Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 07/14] cred: Move call_rcu() to call_rcu_lazy() Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 08/14] security: " Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 09/14] net/core: " Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 10/14] kernel: Move various core kernel usages " Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 11/14] lib: Move call_rcu() " Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 12/14] i915: " Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 13/14] fork: Move thread_stack_free_rcu to call_rcu_lazy Joel Fernandes (Google)
2022-08-19 20:48 ` [PATCH v4 14/14] rcu/tree: Move trace_rcu_callback() before bypassing Joel Fernandes (Google)
2022-08-29 13:40 ` [PATCH v4 00/14] Implement call_rcu_lazy() and miscellaneous fixes Frederic Weisbecker
2022-08-29 16:45 ` Joel Fernandes
2022-08-29 19:46 ` Frederic Weisbecker
2022-08-29 20:31 ` Paul E. McKenney
2022-08-29 20:54 ` Joel Fernandes
2022-08-30 10:50 ` Frederic Weisbecker
2022-08-30 11:47 ` Paul E. McKenney
2022-08-29 20:36 ` Joel Fernandes
2022-08-29 20:42 ` Paul E. McKenney
2022-08-29 20:48 ` Joel Fernandes
2022-08-30 10:57 ` Frederic Weisbecker
2022-08-30 10:53 ` Frederic Weisbecker
2022-08-30 11:43 ` Paul E. McKenney
2022-08-30 16:03 ` Frederic Weisbecker
2022-08-30 16:22 ` Frederic Weisbecker
2022-08-30 16:44 ` Uladzislau Rezki [this message]
2022-08-30 18:53 ` Joel Fernandes
2022-09-01 11:29 ` Frederic Weisbecker
2022-09-01 11:59 ` Uladzislau Rezki
2022-09-01 14:41 ` Paul E. McKenney
2022-09-01 15:30 ` Frederic Weisbecker
2022-09-01 16:11 ` Joel Fernandes
2022-09-01 16:52 ` Paul E. McKenney
2022-09-01 15:13 ` Frederic Weisbecker
2022-09-01 16:07 ` Joel Fernandes
2022-08-30 16:46 ` Paul E. McKenney
2022-08-31 15:26 ` Frederic Weisbecker
2022-09-01 14:39 ` Paul E. McKenney
2022-09-01 14:58 ` Frederic Weisbecker
2022-09-01 16:07 ` Joel Fernandes
2022-09-01 16:49 ` Paul E. McKenney
2022-09-01 18:28 ` Frederic Weisbecker
2022-09-01 20:36 ` Paul E. McKenney
2022-08-30 18:46 ` Joel Fernandes
2022-08-30 10:26 ` Frederic Weisbecker
2022-08-30 18:40 ` Joel Fernandes
2022-08-29 19:57 ` Paul E. McKenney
2022-08-30 10:43 ` Frederic Weisbecker
2022-08-30 12:08 ` Paul E. McKenney
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