From: Oleg Nesterov <oleg@redhat.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Peter Zijlstra <peterz@infradead.org>,
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: Fri, 5 Jun 2015 23:08:57 +0200 [thread overview]
Message-ID: <20150605210857.GA24905@redhat.com> (raw)
In-Reply-To: <20150605014558.GS7232@ZenIV.linux.org.uk>
On 06/05, Al Viro wrote:
>
> FWIW, I hadn't really looked into stop_machine uses, but fs/locks.c one
> is really not all that great - there we have a large trashcan of a list
> (every file_lock on the system) and the only use of that list is /proc/locks
> output generation. Sure, additions take this CPU's spinlock. And removals
> take pretty much a random one - losing the timeslice and regaining it on
> a different CPU is quite likely with the uses there.
>
> Why do we need a global lock there, anyway? Why not hold only one for
> the chain currently being traversed? Sure, we'll need to get and drop
> them in ->next() that way; so what?
And note that fs/seq_file.c:seq_hlist_next_percpu() has no other users.
And given that locks_delete_global_locks() takes the random lock anyway,
perhaps the hashed lists/locking makes no sense, I dunno.
Oleg.
next prev parent reply other threads:[~2015-06-05 21:09 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
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 [this message]
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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