From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752300AbZEaXur (ORCPT ); Sun, 31 May 2009 19:50:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751597AbZEaXul (ORCPT ); Sun, 31 May 2009 19:50:41 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:39232 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751469AbZEaXuk (ORCPT ); Sun, 31 May 2009 19:50:40 -0400 Date: Sun, 31 May 2009 16:50:26 -0700 From: Andrew Morton To: Linus Torvalds Cc: Alexey Dobriyan , Matt Helsley , xemul@parallels.com, containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, dave@linux.vnet.ibm.com, mingo@elte.hu Subject: Re: [PATCH 14/38] Remove struct mm_struct::exe_file et al Message-Id: <20090531165026.376a914c.akpm@linux-foundation.org> In-Reply-To: References: <20090526113618.GJ28083@us.ibm.com> <20090526162415.fb9cefef.akpm@linux-foundation.org> <20090531215427.GA29534@x200.localdomain> <20090531151953.8f8b14b5.akpm@linux-foundation.org> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 31 May 2009 16:15:50 -0700 (PDT) Linus Torvalds wrote: > > > On Sun, 31 May 2009, Andrew Morton wrote: > > > > What I always find a bit weird is that an MM container is used as the > > central point for a number of sched obects. But it's logical, given > > that the never-before-stated definition of a heavyweight process is > > "thing which share a VM". > > It has nothing to do with "heavy-weight process" or anything else. > > The thing is, from a scheduling standpoint, one of the primary performance > concerns in the TLB switch. > > And there's a 1:1 relationship between TLB switch and MM container, modulo > the issue of kernel tasks (and those obviously "borrow" approproate MM > structs to avoid the switch). That's all an obscure performance-oriented internal implementation detail. > So it's not weird at all. It's very direct, and a very straightforward and > obvious relationship. It's arbitrary! If we were to gain more performance benefit by aggregating processes under, say, the fs_struct then that's the way the kernel would have been implemented.