From: jon ernst Subject: difference between xip and o_direct. Date: Thu, 5 Dec 2013 17:47:52 -0500 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: "linux-ext4@vger.kernel.org List" Return-path: Received: from mail-qc0-f176.google.com ([209.85.216.176]:40012 "EHLO mail-qc0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754369Ab3LEWrx (ORCPT ); Thu, 5 Dec 2013 17:47:53 -0500 Received: by mail-qc0-f176.google.com with SMTP id i8so5539514qcq.35 for ; Thu, 05 Dec 2013 14:47:53 -0800 (PST) Sender: linux-ext4-owner@vger.kernel.org List-ID: Hi, I am trying to understand difference between xip and o_direct. For XIP, document xip.txt says "instead of keeping data in the page cache, the need to have a page cache copy is eliminated completely. With execute-in-place, read&write type operations are performed directly from/to the memory backed storage device." For O_Direct, " File I/O is done directly to/from user- space buffers. " from manual of open(2) So, are those 2 trying to do the same thing ? The difference I can tell is, XIP option can be used when mounting fs. O_Direct is used in open system-call. Can anybody kindly teach me what are other differences? thank you! Jon