From: Waiman Long <waiman.long@hpe.com>
To: Christoph Lameter <cl@linux.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Dave Chinner <david@fromorbit.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Jan Kara <jack@suse.com>, Jeff Layton <jlayton@poochiereds.net>,
"J. Bruce Fields" <bfields@fieldses.org>,
Tejun Heo <tj@kernel.org>, <linux-fsdevel@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>,
Andi Kleen <andi@firstfloor.org>,
Dave Chinner <dchinner@redhat.com>,
Scott J Norton <scott.norton@hp.com>,
Douglas Hatch <doug.hatch@hp.com>
Subject: Re: [RFC PATCH 1/2] lib/percpu-list: Per-cpu list with associated per-cpu locks
Date: Wed, 17 Feb 2016 12:12:57 -0500 [thread overview]
Message-ID: <56C4AA19.1080907@hpe.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1602171027310.14247@east.gentwo.org>
On 02/17/2016 11:27 AM, Christoph Lameter wrote:
> On Wed, 17 Feb 2016, Waiman Long wrote:
>
>> I know we can use RCU for singly linked list, but I don't think we can use
>> that for doubly linked list as there is no easy way to make atomic changes to
>> both prev and next pointers simultaneously unless you are taking about 16b
>> cmpxchg which is only supported in some architecture.
> But its supported in the most important architecutes. You can fall back to
> spinlocks on the ones that do not support it.
>
I guess with some limitations on how the lists can be traversed, we may
be able to do that with RCU without lock. However, that will make the
code more complex and harder to verify. Given that in both my and Dave's
testing that contentions with list insertion and deletion are almost
gone from the perf profile when they used to be a bottleneck, is it
really worth the effort to do such a conversion?
Cheers,
Longman
next prev parent reply other threads:[~2016-02-17 17:13 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-17 1:31 [RFC PATCH 0/2] vfs: Use per-cpu list for SB's s_inodes list Waiman Long
2016-02-17 1:31 ` [RFC PATCH 1/2] lib/percpu-list: Per-cpu list with associated per-cpu locks Waiman Long
2016-02-17 9:53 ` Dave Chinner
2016-02-17 11:00 ` Peter Zijlstra
2016-02-17 11:05 ` Peter Zijlstra
2016-02-17 16:16 ` Waiman Long
2016-02-17 16:22 ` Peter Zijlstra
2016-02-17 16:27 ` Christoph Lameter
2016-02-17 17:12 ` Waiman Long [this message]
2016-02-17 17:18 ` Peter Zijlstra
2016-02-17 17:41 ` Waiman Long
2016-02-17 18:22 ` Peter Zijlstra
2016-02-17 18:45 ` Waiman Long
2016-02-17 19:39 ` Peter Zijlstra
2016-02-17 11:10 ` Dave Chinner
2016-02-17 11:26 ` Peter Zijlstra
2016-02-17 11:36 ` Peter Zijlstra
2016-02-17 15:56 ` Waiman Long
2016-02-17 16:02 ` Peter Zijlstra
2016-02-17 15:13 ` Christoph Lameter
2016-02-17 1:31 ` [RRC PATCH 2/2] vfs: Use per-cpu list for superblock's inode list Waiman Long
2016-02-17 7:16 ` Ingo Molnar
2016-02-17 15:40 ` Waiman Long
2016-02-17 10:37 ` Dave Chinner
2016-02-17 16:08 ` Waiman Long
2016-02-18 23:58 ` [RFC PATCH 0/2] vfs: Use per-cpu list for SB's s_inodes list Dave Chinner
2016-02-19 21:04 ` Long, Wai Man
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