From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754614Ab3AYCJ6 (ORCPT ); Thu, 24 Jan 2013 21:09:58 -0500 Received: from mail-qc0-f179.google.com ([209.85.216.179]:42525 "EHLO mail-qc0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754026Ab3AYCJu (ORCPT ); Thu, 24 Jan 2013 21:09:50 -0500 Date: Thu, 24 Jan 2013 18:09:43 -0800 From: Tejun Heo To: Kent Overstreet Cc: linux-kernel@vger.kernel.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, zab@redhat.com, bcrl@kvack.org, jmoyer@redhat.com, axboe@kernel.dk, viro@zeniv.linux.org.uk, tytso@mit.edu, Oleg Nesterov , srivatsa.bhat@linux.vnet.ibm.com, Christoph Lameter , "Paul E. McKenney" , Rusty Russell Subject: Re: [PATCH 23/32] Generic dynamic per cpu refcounting Message-ID: <20130125020943.GH2373@mtj.dyndns.org> References: <1356573611-18590-1-git-send-email-koverstreet@google.com> <1356573611-18590-26-git-send-email-koverstreet@google.com> <20130125005136.GE2373@mtj.dyndns.org> <20130125011345.GT26407@google.com> <20130125020340.GG2373@mtj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130125020340.GG2373@mtj.dyndns.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, again. On Thu, Jan 24, 2013 at 06:03:40PM -0800, Tejun Heo wrote: > Yeah, if we're aiming to replace refcnts in file and kobj, dynamic > alloc may be justified. Hopefully, the accounting necessary to decide > whethre to use percpu isn't too burdensome. Ooh, I forgot one thing. We might not gain much by replacing file refcnt w/ this. You can't really get cheaper than fget_light(). Also, while kobj destruction can still be considered an infrequent operation, file destruction is not and people will get mighty unhappy if you do synchronize_sched/rcu() from fput() synchronously. So, I'm now back to "do we need dynamic allocation". What else do we have to convert? Thanks. -- tejun