From: Peter Zijlstra <peterz@infradead.org>
To: Quentin Perret <quentin.perret@arm.com>
Cc: Morten Rasmussen <morten.rasmussen@foss.arm.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
mingo@redhat.com, valentin.schneider@arm.com,
dietmar.eggemann@arm.com, vincent.guittot@linaro.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/7] sched: Add static_key for asymmetric cpu capacity optimizations
Date: Fri, 16 Feb 2018 18:43:55 +0100 [thread overview]
Message-ID: <20180216174355.GK25201@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180216173927.GA5352@e108498-lin.cambridge.arm.com>
On Fri, Feb 16, 2018 at 05:39:27PM +0000, Quentin Perret wrote:
> AFAIU it should be safe, but without your check you'll have to go through
> cpus_read_lock()/unlock() every time a CPU is hotplugged. There is probably
> no good reason to re-do that again and again if the state of the key
> never changes. I don't know how expensive those lock/unlock operations are,
> but I bet they are more expensive than testing static_branch_unlikely() :)
This is not a performance critical path, more obvious code is more
better.
Also cpus_read_lock() is dirt cheap most of the time.
next prev parent reply other threads:[~2018-02-16 17:44 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-15 16:20 [PATCH 0/7] sched/fair: Migrate 'misfit' tasks on asymmetric capacity systems Morten Rasmussen
2018-02-15 16:20 ` [PATCH 1/7] sched: Add static_key for asymmetric cpu capacity optimizations Morten Rasmussen
2018-02-16 13:47 ` Peter Zijlstra
2018-02-16 15:41 ` Morten Rasmussen
2018-02-16 16:51 ` Peter Zijlstra
2018-02-19 11:49 ` Morten Rasmussen
2018-02-16 17:39 ` Quentin Perret
2018-02-16 17:43 ` Peter Zijlstra [this message]
2018-02-15 16:20 ` [PATCH 2/7] sched/fair: Add group_misfit_task load-balance type Morten Rasmussen
2018-02-19 13:56 ` Peter Zijlstra
2018-02-19 13:58 ` Peter Zijlstra
2018-02-20 16:01 ` Morten Rasmussen
2018-02-15 16:20 ` [PATCH 3/7] sched/fair: Consider misfit tasks when load-balancing Morten Rasmussen
2018-02-15 16:20 ` [PATCH 4/7] sched/fair: Avoid unnecessary balancing of asymmetric capacity groups Morten Rasmussen
2018-02-19 14:50 ` Peter Zijlstra
2018-02-19 14:53 ` Peter Zijlstra
2018-02-20 16:22 ` Morten Rasmussen
2018-02-19 15:10 ` Peter Zijlstra
2018-02-20 16:33 ` Morten Rasmussen
2018-02-20 18:26 ` Peter Zijlstra
2018-02-23 16:38 ` Morten Rasmussen
2018-02-23 16:47 ` Peter Zijlstra
2018-02-26 15:06 ` Morten Rasmussen
2018-02-15 16:20 ` [PATCH 5/7] sched/fair: Kick nohz balance if rq->misfit_task Morten Rasmussen
2018-02-15 16:20 ` [PATCH 6/7] sched: Rename root_domain->overload to should_idle_balance Morten Rasmussen
2018-02-16 9:14 ` Juri Lelli
2018-02-16 9:49 ` Peter Zijlstra
2018-02-16 11:59 ` Valentin Schneider
2018-02-15 16:20 ` [PATCH 7/7] sched/fair: Set sd->should_idle_balance when misfit Morten Rasmussen
2018-02-28 7:46 ` [PATCH 0/7] sched/fair: Migrate 'misfit' tasks on asymmetric capacity systems Gaku Inami
2018-03-01 11:59 ` 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=20180216174355.GK25201@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=dietmar.eggemann@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=morten.rasmussen@arm.com \
--cc=morten.rasmussen@foss.arm.com \
--cc=quentin.perret@arm.com \
--cc=valentin.schneider@arm.com \
--cc=vincent.guittot@linaro.org \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.