From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757741Ab3HMXD6 (ORCPT ); Tue, 13 Aug 2013 19:03:58 -0400 Received: from mail-qc0-f173.google.com ([209.85.216.173]:64135 "EHLO mail-qc0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752708Ab3HMXD4 (ORCPT ); Tue, 13 Aug 2013 19:03:56 -0400 Date: Tue, 13 Aug 2013 19:03:52 -0400 From: Tejun Heo To: Andrew Morton Cc: Chris Metcalf , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Thomas Gleixner , Frederic Weisbecker , Cody P Schafer Subject: Re: [PATCH v4 2/2] mm: make lru_add_drain_all() selective Message-ID: <20130813230352.GH28996@mtj.dyndns.org> References: <52099187.80301@tilera.com> <20130813123512.3d6865d8bf4689c05d44738c@linux-foundation.org> <20130813201958.GA28996@mtj.dyndns.org> <20130813133135.3b580af557d1457e4ee8331a@linux-foundation.org> <20130813210719.GB28996@mtj.dyndns.org> <20130813141621.3f1c3415901d4236942ee736@linux-foundation.org> <20130813220700.GC28996@mtj.dyndns.org> <20130813151805.b1177b60cba5b127b2aa6aee@linux-foundation.org> <20130813223304.GF28996@mtj.dyndns.org> <20130813154740.5daa053df87dd0358bbbab35@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130813154740.5daa053df87dd0358bbbab35@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 Hello, Andrew. On Tue, Aug 13, 2013 at 03:47:40PM -0700, Andrew Morton wrote: > > Well, I don't buy that either. Callback based interface has its > > issues. > > No it hasn't. It's a common and simple technique which we all understand. It sure has its uses but it has receded some of its former use cases to better constructs which are easier to use and maintain. I'm not saying it's black and white here as the thing is callback based anyway but was trying to point out general disadvantages of callback based interface. If you're saying callback based interface isn't clunkier compared to constructs which can be embedded in the caller side, this discussion probably won't be very fruitful. > It's a relatively small improvement in the lru_add_drain_all() case. > Other callsites can gain improvements as well. Well, if we're talking about minute performance differences, for non-huge configurations, it'll actually be a small performance degradation as there will be more instructions and the control will be jumping back and forth. > It results in superior runtime code. At this and potentially other > callsites. It's actually inferior in majority of cases. > It does buy us things, as I've repeatedly described. You keep on > saying things which demonstrably aren't so. I think I'll give up now. I just don't think it's something clear cut and it doesn't even matter for the problem at hand. Let's please talk about how to solve the actual problem. Thanks. -- tejun From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx183.postini.com [74.125.245.183]) by kanga.kvack.org (Postfix) with SMTP id 1C1896B0032 for ; Tue, 13 Aug 2013 19:03:57 -0400 (EDT) Received: by mail-qa0-f50.google.com with SMTP id f14so656635qak.2 for ; Tue, 13 Aug 2013 16:03:56 -0700 (PDT) Date: Tue, 13 Aug 2013 19:03:52 -0400 From: Tejun Heo Subject: Re: [PATCH v4 2/2] mm: make lru_add_drain_all() selective Message-ID: <20130813230352.GH28996@mtj.dyndns.org> References: <52099187.80301@tilera.com> <20130813123512.3d6865d8bf4689c05d44738c@linux-foundation.org> <20130813201958.GA28996@mtj.dyndns.org> <20130813133135.3b580af557d1457e4ee8331a@linux-foundation.org> <20130813210719.GB28996@mtj.dyndns.org> <20130813141621.3f1c3415901d4236942ee736@linux-foundation.org> <20130813220700.GC28996@mtj.dyndns.org> <20130813151805.b1177b60cba5b127b2aa6aee@linux-foundation.org> <20130813223304.GF28996@mtj.dyndns.org> <20130813154740.5daa053df87dd0358bbbab35@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130813154740.5daa053df87dd0358bbbab35@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Chris Metcalf , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Thomas Gleixner , Frederic Weisbecker , Cody P Schafer Hello, Andrew. On Tue, Aug 13, 2013 at 03:47:40PM -0700, Andrew Morton wrote: > > Well, I don't buy that either. Callback based interface has its > > issues. > > No it hasn't. It's a common and simple technique which we all understand. It sure has its uses but it has receded some of its former use cases to better constructs which are easier to use and maintain. I'm not saying it's black and white here as the thing is callback based anyway but was trying to point out general disadvantages of callback based interface. If you're saying callback based interface isn't clunkier compared to constructs which can be embedded in the caller side, this discussion probably won't be very fruitful. > It's a relatively small improvement in the lru_add_drain_all() case. > Other callsites can gain improvements as well. Well, if we're talking about minute performance differences, for non-huge configurations, it'll actually be a small performance degradation as there will be more instructions and the control will be jumping back and forth. > It results in superior runtime code. At this and potentially other > callsites. It's actually inferior in majority of cases. > It does buy us things, as I've repeatedly described. You keep on > saying things which demonstrably aren't so. I think I'll give up now. I just don't think it's something clear cut and it doesn't even matter for the problem at hand. Let's please talk about how to solve the actual problem. Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org