From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753323AbZFAACZ (ORCPT ); Sun, 31 May 2009 20:02:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751783AbZFAACR (ORCPT ); Sun, 31 May 2009 20:02:17 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:35705 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751684AbZFAACQ (ORCPT ); Sun, 31 May 2009 20:02:16 -0400 Date: Sun, 31 May 2009 17:02:03 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Andrew Morton 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 In-Reply-To: <20090531165026.376a914c.akpm@linux-foundation.org> Message-ID: References: <20090526113618.GJ28083@us.ibm.com> <20090526162415.fb9cefef.akpm@linux-foundation.org> <20090531215427.GA29534@x200.localdomain> <20090531151953.8f8b14b5.akpm@linux-foundation.org> <20090531165026.376a914c.akpm@linux-foundation.org> User-Agent: Alpine 2.01 (LFD 1184 2008-12-16) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 31 May 2009, Andrew Morton wrote: > > 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. What? That's like saying that "if quarks were the size of soccer-balls, we'd all be pink". It makes no sense. When you claim that it's arbitrary, you're totally ignoring reality, and CPU design. The fact is, TLB's are very fundamental to task switching. filesystems are not. It's that simple. IOW, it's not at all arbitrary, it's a direct result of how the world works. The "world" for the kernel is the reality of CPU's, and in that reality, TLB switching is a huge factor. There is nothing arbitrary about it at all. Linus