Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 10 Aug 2002 12:58:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 10 Aug 2002 12:58:09 -0400 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:7440 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id ; Sat, 10 Aug 2002 12:58:09 -0400 Date: Sat, 10 Aug 2002 10:03:09 -0700 (PDT) From: Linus Torvalds To: Rik van Riel cc: Andrew Morton , lkml Subject: Re: [patch 6/12] hold atomic kmaps across generic_file_read In-Reply-To: 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: 972 Lines: 27 On Sat, 10 Aug 2002, Rik van Riel wrote: > On Sat, 10 Aug 2002, Linus Torvalds wrote: > > > and having it magically populate the VM directly with the whole file > > mapping, with _one_ failed page fault. And the above is actually a fairly > > common thing. See how many people have tried to optimize using mmap vs > > read, and what they _all_ really wanted was this "populate the pages in > > one go" thing. > > If this is worth it, chances are prefaulting at mmap() time > could also be worth trying ... hmmm ;) Maybe, maybe not. The advantage of read() is that it contains an implicit "madvise()", since the read _tells_ us that it wants X pages. A page fault does not tell us, and prefaulting can hurt us. 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/