From: Andrew Morton <akpm@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Ingo Molnar <mingo@kernel.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/6] Optimize the cpu hotplug locking -v2
Date: Wed, 9 Oct 2013 22:50:06 -0700 [thread overview]
Message-ID: <20131009225006.7101379c.akpm@linux-foundation.org> (raw)
In-Reply-To: <20131008102505.404025673@infradead.org>
On Tue, 08 Oct 2013 12:25:05 +0200 Peter Zijlstra <peterz@infradead.org> wrote:
> The current cpu hotplug lock is a single global lock; therefore excluding
> hotplug is a very expensive proposition even though it is rare occurrence under
> normal operation.
>
> There is a desire for a more light weight implementation of
> {get,put}_online_cpus() from both the NUMA scheduling as well as the -RT side.
>
> The current hotplug lock is a full reader preference lock -- and thus supports
> reader recursion. However since we're making the read side lock much cheaper it
> is the expectation that it will also be used far more. Which in turn would lead
> to writer starvation.
>
> Therefore the new lock proposed is completely fair; albeit somewhat expensive
> on the write side. This in turn means that we need a per-task nesting count to
> support reader recursion.
This is a lot of code and a lot of new complexity. It needs some pretty
convincing performance numbers to justify its inclusion, no?
next prev parent reply other threads:[~2013-10-10 5:49 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-08 10:25 [PATCH 0/6] Optimize the cpu hotplug locking -v2 Peter Zijlstra
2013-10-08 10:25 ` [PATCH 1/6] hotplug: Optimize {get,put}_online_cpus() Peter Zijlstra
2013-10-08 15:08 ` Rik van Riel
2013-10-10 5:47 ` Andrew Morton
2013-10-10 11:06 ` Oleg Nesterov
2013-10-10 14:55 ` Paul E. McKenney
2013-10-08 10:25 ` [PATCH 2/6] rcu: Create rcu_sync infrastructure Peter Zijlstra
2013-10-08 20:40 ` Jonathan Corbet
2013-10-09 19:52 ` Peter Zijlstra
2013-10-17 2:56 ` Lai Jiangshan
2013-10-17 10:36 ` Srikar Dronamraju
2013-10-08 10:25 ` [PATCH 3/6] hotplug: Optimize cpu_hotplug_{begin,done}() using rcu_sync Peter Zijlstra
2013-10-08 16:28 ` Paul E. McKenney
2013-10-08 10:25 ` [PATCH 4/6] rcusync: Introduce struct rcu_sync_ops Peter Zijlstra
2013-10-08 16:30 ` Paul E. McKenney
2013-10-17 2:07 ` Lai Jiangshan
[not found] ` <20131017154228.GL4553@linux.vnet.ibm.com>
2013-10-18 1:23 ` Lai Jiangshan
2013-10-18 12:10 ` Oleg Nesterov
2013-10-20 16:58 ` Paul E. McKenney
2013-10-08 10:25 ` [PATCH 5/6] rcusync: Add the CONFIG_PROVE_RCU checks Peter Zijlstra
2013-10-08 16:30 ` Paul E. McKenney
2013-10-08 10:25 ` [PATCH 6/6] rcusync: Introduce rcu_sync_dtor() Peter Zijlstra
2013-10-08 16:32 ` Paul E. McKenney
2013-10-08 15:27 ` [PATCH 0/6] Optimize the cpu hotplug locking -v2 Oleg Nesterov
2013-10-08 15:38 ` Peter Zijlstra
2013-10-10 5:50 ` Andrew Morton [this message]
2013-10-10 6:27 ` Ingo Molnar
2013-10-10 6:34 ` Andrew Morton
2013-10-10 7:27 ` Ingo Molnar
2013-10-10 7:33 ` Andrew Morton
2013-10-10 7:45 ` Ingo Molnar
2013-10-10 12:19 ` Peter Zijlstra
2013-10-10 14:57 ` Ingo Molnar
2013-10-10 15:21 ` Peter Zijlstra
2013-10-10 15:36 ` Oleg Nesterov
2013-10-10 16:50 ` Ingo Molnar
2013-10-10 17:13 ` Paul E. McKenney
2013-10-10 17:35 ` Ingo Molnar
2013-10-10 18:35 ` Peter Zijlstra
2013-10-10 15:26 ` Oleg Nesterov
2013-10-10 16:00 ` Andrew Morton
2013-10-10 16:36 ` Steven Rostedt
2013-10-10 16:43 ` Andrew Morton
2013-10-10 16:53 ` Peter Zijlstra
2013-10-10 17:13 ` Steven Rostedt
2013-10-10 17:48 ` Andrew Morton
2013-10-10 18:10 ` Linus Torvalds
2013-10-10 18:43 ` Steven Rostedt
2013-10-10 18:50 ` Peter Zijlstra
2013-10-10 19:15 ` Paul E. McKenney
2013-10-10 19:00 ` Linus Torvalds
2013-10-10 18:46 ` Peter Zijlstra
2013-10-10 18:34 ` Peter Zijlstra
2013-10-10 18:49 ` Linus Torvalds
2013-10-10 19:04 ` Steven Rostedt
2013-10-10 19:16 ` Linus Torvalds
2013-10-10 19:34 ` Peter Zijlstra
2013-10-10 19:34 ` Steven Rostedt
2013-10-11 6:09 ` Ingo Molnar
2013-10-11 12:38 ` Peter Zijlstra
2013-10-11 18:25 ` Oleg Nesterov
2013-10-11 20:48 ` Peter Zijlstra
2013-10-12 17:06 ` Oleg Nesterov
2013-10-14 9:05 ` Peter Zijlstra
2013-10-14 9:23 ` Paul E. McKenney
2013-10-15 1:01 ` Paul E. McKenney
2013-10-17 16:49 ` [tip:sched/core] sched: Remove get_online_cpus() usage tip-bot for Peter Zijlstra
2013-10-10 17:39 ` [PATCH 0/6] Optimize the cpu hotplug locking -v2 Oleg Nesterov
2013-10-10 16:52 ` Ingo Molnar
2013-10-10 17:44 ` Paul E. McKenney
2013-10-10 16:54 ` Oleg Nesterov
2013-10-10 19:04 ` Srivatsa S. Bhat
2013-10-10 18:52 ` Srivatsa S. Bhat
-- strict thread matches above, loose matches on Subject: below --
2013-10-11 12:14 George Spelvin
2013-10-11 12:45 ` Steven Rostedt
2013-10-11 13:51 ` George Spelvin
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=20131009225006.7101379c.akpm@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=aarcange@redhat.com \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=riel@redhat.com \
--cc=rostedt@goodmis.org \
--cc=srikar@linux.vnet.ibm.com \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.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.