From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ppp-217-133-42-200.cust-adsl.tiscali.it ([217.133.42.200]:6341 "EHLO dualathlon.random") by vger.kernel.org with ESMTP id S262527AbUCWMds (ORCPT ); Tue, 23 Mar 2004 07:33:48 -0500 Date: Tue, 23 Mar 2004 13:34:39 +0100 From: Andrea Arcangeli Subject: Re: can device drivers return non-ram via vm_ops->nopage? Message-ID: <20040323123439.GJ22639@dualathlon.random> References: <1079967870.1759.12.camel@mulgrave> <20040322151533.C11212@flint.arm.linux.org.uk> <1079969221.1759.25.camel@mulgrave> <1079992229.22190.29.camel@gaston> <405F6636.2090609@pobox.com> <20040322223509.GO2045@holomorphy.com> <1079999839.23205.40.camel@gaston> <20040323020756.GS2045@holomorphy.com> <20040323113534.GD22639@dualathlon.random> <20040323114452.GE2045@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040323114452.GE2045@holomorphy.com> To: William Lee Irwin III Cc: Benjamin Herrenschmidt , Jeff Garzik , James Bottomley , Russell King , Linux Arch list , Linus Torvalds , David Woodhouse , Christoph Hellwig , Andrew Morton List-ID: On Tue, Mar 23, 2004 at 03:44:52AM -0800, William Lee Irwin III wrote: > mlock actually loops through the fault path, so in a sense it still > requires fault handling on the part of the driver, though AFAICT it can it requires fault handling of course, but that's just the API with the driver, on the performance side (and it was the performance/latency side of the page faults to be complained) no page faults are generated, so it's not going to be a lot different from the map_sg stuff at runtime. anyways Linus vetoed the lazy approch so we probably should give it up (the one thing I like most is to avoid the branch in the fast path).