From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw0-f193.google.com ([209.85.161.193]:36397 "EHLO mail-yw0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751051AbcGNOvM (ORCPT ); Thu, 14 Jul 2016 10:51:12 -0400 Date: Thu, 14 Jul 2016 10:51:09 -0400 From: Tejun Heo To: Jan Kara Cc: Waiman Long , Alexander Viro , Jan Kara , Jeff Layton , "J. Bruce Fields" , Christoph Lameter , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Andi Kleen , Dave Chinner , Boqun Feng , Scott J Norton , Douglas Hatch Subject: Re: [PATCH v2 1/7] lib/dlock-list: Distributed and lock-protected lists Message-ID: <20160714145109.GI15005@htj.duckdns.org> References: <1468258332-61537-1-git-send-email-Waiman.Long@hpe.com> <1468258332-61537-2-git-send-email-Waiman.Long@hpe.com> <20160713160823.GD4065@mtj.duckdns.org> <5786FEDB.9080107@hpe.com> <20160714115043.GD15005@htj.duckdns.org> <20160714143547.GE13151@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160714143547.GE13151@quack2.suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Hello, Jan. On Thu, Jul 14, 2016 at 04:35:47PM +0200, Jan Kara wrote: > > > The current use case only need to use the regular lock functions. You are > > > right that future use cases may require an irqsafe version of locks. I can > > > either modify the code now to allow lock type selection at init time, for > > > example, or defer it as a future enhancement when the need arises. What do > > > you think? > > > > The bulk of performance gain of dlist would come from being per-cpu > > and I don't think it's likely that we'd see any noticeable difference > > between irq and preempt safe operations. Given that what's being > > implemented is really low level operations, I'd suggest going with > > irqsafe from the get-go. > > I'm not sure here. i_sb_list for which percpu lists will be used is bashed > pretty heavily under some workloads and the cost of additional interrupt > disabling & enabling may be visible under those loads. Probably not in the > cases where you get a boost from percpu lists but if the workload is mostly > single-threaded, additional cpu cost may be measurable. So IMO we should > check whether a load which creates tons of empty inodes in tmpfs from a > single process doesn't regress with this change. Sure, if it actually matters, we can always create separate preempt / irq variants. Thanks. -- tejun