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From: Davidlohr Bueso <dave@stgolabs.net>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Oleg Nesterov <oleg@redhat.com>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	Tejun Heo <tj@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	der.herr@hofr.at
Subject: Re: [RFC][PATCH 0/5] Optimize percpu-rwsem
Date: Tue, 26 May 2015 11:42:11 -0700	[thread overview]
Message-ID: <1432665731.8196.3.camel@stgolabs.net> (raw)
In-Reply-To: <CA+55aFwxjAWTm9XZg0ZE6kB70S8iKV6b8RQL8Bi6fapaPbwpRQ@mail.gmail.com>

On Tue, 2015-05-26 at 11:12 -0700, Linus Torvalds wrote:
> On Tue, May 26, 2015 at 4:43 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > This is a derived work of the cpu hotplug lock rework I did in 2013 which never
> > really went anywhere because Linus didn't like it.
> >
> > This applies those same optimizations to the percpu-rwsem. Seeing how we did
> > all the work it seemed a waste to not use it at all.
> 
> So I *still* don't like it.
> 
> We literally have one single percpu-rwsem IN THE WHOLE KERNEL TREE.
> 
> One.
> 
> Not "a couple". Not "hundreds". ONE.

Instead of dropping percpu-rwsem, I was thinking we could instead look
for opportunities to convert new users, for instance shinkers, where the
write lock is also taken just for register and unregister purposes,
similar to uprobes.

Thanks,
Davidlohr


  parent reply	other threads:[~2015-05-26 18:42 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-26 11:43 [RFC][PATCH 0/5] Optimize percpu-rwsem Peter Zijlstra
2015-05-26 11:43 ` [RFC][PATCH 1/5] rcu: Create rcu_sync infrastructure Peter Zijlstra
2015-05-30 16:58   ` Paul E. McKenney
2015-05-30 19:16     ` Oleg Nesterov
2015-05-30 19:25       ` Oleg Nesterov
2015-05-31 16:07       ` Paul E. McKenney
2015-05-26 11:43 ` [RFC][PATCH 2/5] rcusync: Introduce struct rcu_sync_ops Peter Zijlstra
2015-05-26 11:43 ` [RFC][PATCH 3/5] rcusync: Add the CONFIG_PROVE_RCU checks Peter Zijlstra
2015-05-26 11:44 ` [RFC][PATCH 4/5] rcusync: Introduce rcu_sync_dtor() Peter Zijlstra
2015-05-26 11:44 ` [RFC][PATCH 5/5] percpu-rwsem: Optimize readers and reduce global impact Peter Zijlstra
2015-05-29 19:45   ` Oleg Nesterov
2015-05-29 20:09     ` Oleg Nesterov
2015-05-29 20:41       ` Linus Torvalds
2015-05-30 20:49         ` Oleg Nesterov
2015-06-16 11:48           ` Peter Zijlstra
2015-05-30 17:18   ` Paul E. McKenney
2015-05-30 20:04     ` ring_buffer_attach && cond_synchronize_rcu (Was: percpu-rwsem: Optimize readers and reduce global impact) Oleg Nesterov
2015-06-16 11:08       ` Peter Zijlstra
2015-06-16 11:16         ` Peter Zijlstra
2015-06-16 19:03           ` Oleg Nesterov
2015-06-19 17:57       ` [tip:perf/urgent] perf: Fix ring_buffer_attach() RCU sync, again tip-bot for Oleg Nesterov
2015-05-26 18:12 ` [RFC][PATCH 0/5] Optimize percpu-rwsem Linus Torvalds
2015-05-26 18:34   ` Peter Zijlstra
2015-05-26 18:35   ` Tejun Heo
2015-05-26 18:42   ` Davidlohr Bueso [this message]
2015-05-26 21:57     ` Linus Torvalds
2015-05-27  9:28       ` Nicholas Mc Guire
2015-06-05  1:45       ` Al Viro
2015-06-05 21:08         ` Oleg Nesterov
2015-06-05 22:11           ` Al Viro
2015-06-05 23:36             ` Oleg Nesterov
2015-05-27  6:53     ` Peter Zijlstra
2015-05-26 18:57   ` Oleg Nesterov
2015-05-26 19:13     ` Oleg Nesterov
2015-05-26 19:29     ` Oleg Nesterov
2015-05-26 19:54 ` Davidlohr Bueso

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