From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753658Ab2HCVoX (ORCPT ); Fri, 3 Aug 2012 17:44:23 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:35588 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753110Ab2HCVoT (ORCPT ); Fri, 3 Aug 2012 17:44:19 -0400 Date: Fri, 3 Aug 2012 14:44:14 -0700 From: Tejun Heo To: Sasha Levin Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, paul.gortmaker@windriver.com, davem@davemloft.net, rostedt@goodmis.org, mingo@elte.hu, ebiederm@xmission.com, aarcange@redhat.com, ericvh@gmail.com, netdev@vger.kernel.org Subject: Re: [RFC v2 1/7] hashtable: introduce a small and naive hashtable Message-ID: <20120803214414.GL15477@google.com> References: <1344003788-1417-1-git-send-email-levinsasha928@gmail.com> <1344003788-1417-2-git-send-email-levinsasha928@gmail.com> <20120803171515.GH15477@google.com> <501C407D.9080900@gmail.com> <20120803213017.GK15477@google.com> <501C4471.4090706@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <501C4471.4090706@gmail.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Sasha. On Fri, Aug 03, 2012 at 11:36:49PM +0200, Sasha Levin wrote: > On 08/03/2012 11:30 PM, Tejun Heo wrote: > The function definition itself is just a macro, for example: > > #define MM_SLOTS_HASH_CMP(mm_slot, obj) ((mm_slot)->mm == (obj)) It seems like it would make things more difficult to follow and error-prone. I'd definitely prefer just using functions. > As an alternative, what do you think about simplifying that to be > just a 'cond' instead of a function? Something like: > > hash_get(&mm_slots_hash, mm, struct mm_slot, hash, mm); > > In that case, the last param ("mm") will get unrolled to a condition like this: > > if ((obj)->mm == key) > > Which will be simple and easy for the user. It seems a bit too magical(tm) to me. ;) > The only reason I want to keep this interface is that most cases > I've stumbled so far were easy short comparisons of a struct member > with the key, and I don't want to make them more complex than they > need to be. I probably will switch hash_get() to use > hash_for_each_possible() as well, which will cut down on how > hash_get() is a separate case. I can understand that but I think the benefit we're talking about is a bit too miniscule to matter and to have two different interfaces. What do others think? Thanks. -- tejun