Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752869AbZDKXvy (ORCPT ); Sat, 11 Apr 2009 19:51:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751951AbZDKXvp (ORCPT ); Sat, 11 Apr 2009 19:51:45 -0400 Received: from srv5.dvmed.net ([207.36.208.214]:43590 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750779AbZDKXvo (ORCPT ); Sat, 11 Apr 2009 19:51:44 -0400 Message-ID: <49E12D03.5070906@garzik.org> Date: Sat, 11 Apr 2009 19:51:31 -0400 From: Jeff Garzik User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Alan Cox CC: Grant Grundler , Linus Torvalds , Linux IDE mailing list , LKML , Jens Axboe , Arjan van de Ven Subject: Re: Implementing NVMHCI... References: <49E0D47B.9070205@garzik.org> <20090411203246.513a0892@lxorguk.ukuu.org.uk> <20090412002527.631a5a89@lxorguk.ukuu.org.uk> In-Reply-To: <20090412002527.631a5a89@lxorguk.ukuu.org.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.4 (----) X-Spam-Report: SpamAssassin version 3.2.5 on srv5.dvmed.net summary: Content analysis details: (-4.4 points, 5.0 required) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1039 Lines: 27 Alan Cox wrote: >> We've abstract the DMA mapping/SG list handling enough that the >> block size should make no more difference than it does for the >> MTU size of a network. > > You need to start managing groups of pages in the vm and keeping them > together and writing them out together and paging them together even if > one of them is dirty and the other isn't. You have to deal with cases > where a process forks and the two pages are dirtied one in each but still > have to be written together. > > Alternatively you go for read-modify-write (nasty performance hit > especially for RAID or a log structured fs). Or just ignore the extra length, thereby excising the 'read-modify' step... Total storage is halved or worse, but you don't take as much of a performance hit. Jeff -- 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/