Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757652Ab3FMWag (ORCPT ); Thu, 13 Jun 2013 18:30:36 -0400 Received: from mail-qa0-f54.google.com ([209.85.216.54]:64929 "EHLO mail-qa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753214Ab3FMWaf (ORCPT ); Thu, 13 Jun 2013 18:30:35 -0400 Date: Thu, 13 Jun 2013 15:30:28 -0700 From: Tejun Heo To: Andrew Morton Cc: Kent Overstreet , linux-kernel@vger.kernel.org, Oleg Nesterov , Christoph Lameter , Ingo Molnar , Andi Kleen , Jens Axboe , "Nicholas A. Bellinger" , Jeff Layton , "J. Bruce Fields" Subject: Re: [PATCH] Percpu tag allocator Message-ID: <20130613223028.GG13970@mtj.dyndns.org> References: <1371009804-11596-1-git-send-email-koverstreet@google.com> <20130612163854.91da28042ab7a943b69a5970@linux-foundation.org> <20130613020536.GA10979@localhost> <20130612200311.7f9d938a.akpm@linux-foundation.org> <20130613185318.GB12075@mtj.dyndns.org> <20130613120439.fe56d178a1143089136fdacc@linux-foundation.org> <20130613191507.GB13970@mtj.dyndns.org> <20130613122339.239a721d097a64435817a780@linux-foundation.org> <20130613193514.GD13970@mtj.dyndns.org> <20130613151040.8e11da022519fff7d5e8ea77@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130613151040.8e11da022519fff7d5e8ea77@linux-foundation.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 Content-Length: 1477 Lines: 35 Hello, Andrew. On Thu, Jun 13, 2013 at 03:10:40PM -0700, Andrew Morton wrote: > Look, we're falling into the age-old trap of trying to justify existing > code just because it exists. > > Stop. Take a step back and pretend that the percpu tag allocator patch > never existed. Now, define the problem and propose solutions. > > The absolute dead last and worst solution is "implement something new > which largely duplicates existing code". Such a step requires an > extraordinary amount of justification and that hasn't happened. I think you're looking at it from the complete opposite point from mine. That problem has always existed and the solutions implemented many times over in the whole IO stack across aio, block layer proper, SCSI and individual drivers, and most, if not all, suck. If we can consolidate those into a properly designed tag allocator, it's a win, whether it's integrated into idr or not. It's a well-known problem with incomplete bad solutions implemented in multiple places. Again, I'm not saying integrating this into idr is a bad idea. If that's reasonably doable, awesomer, but I think even just consolidating the existing bad ones into a common one is beneficial enough. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/