Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 10 Aug 2002 13:41:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 10 Aug 2002 13:41:30 -0400 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:787 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id ; Sat, 10 Aug 2002 13:41:30 -0400 Date: Sat, 10 Aug 2002 10:46:30 -0700 (PDT) From: Linus Torvalds To: Jamie Lokier cc: Andrew Morton , lkml Subject: Re: [patch 6/12] hold atomic kmaps across generic_file_read In-Reply-To: <20020810183604.B306@kushida.apsleyroad.org> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1067 Lines: 32 On Sat, 10 Aug 2002, Jamie Lokier wrote: > > This will only provide the performance benefic when `aligned_malloc' > return "fresh" memory, i.e. memory that has never been written to. Absolutely. Think o fthe optimization as a way to give application writers a new way of being efficient. In particular, I remember when the gcc people were worried about the most efficient way to read in a file for preprocessing (Neil Booth, mainly). Neil did all these timings on where the cut-off point was for using mmap vs just using read(). For people like that, wouldn't it be nice to just be able to tell them: if you do X, we guarantee that you'll get optimal zero-copy performance for reading a file. > But it's a nice way to optimise if you are _deliberately_ optimising a > user space program. Exactly. Linus - 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/