From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id 46A6F6B0031 for ; Mon, 30 Dec 2013 14:40:06 -0500 (EST) Received: by mail-pa0-f53.google.com with SMTP id hz1so11906022pad.40 for ; Mon, 30 Dec 2013 11:40:05 -0800 (PST) Received: from mail-pd0-f169.google.com (mail-pd0-f169.google.com [209.85.192.169]) by mx.google.com with ESMTPS id s4si1784800pbg.303.2013.12.30.11.40.04 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 30 Dec 2013 11:40:04 -0800 (PST) Received: by mail-pd0-f169.google.com with SMTP id v10so11616314pde.14 for ; Mon, 30 Dec 2013 11:40:04 -0800 (PST) References: <52C1C6F7.8010809@intel.com> Mime-Version: 1.0 (1.0) In-Reply-To: <52C1C6F7.8010809@intel.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Message-Id: From: Andreas Dilger Subject: Re: [PATCH 0/3] Fadvise: Directory level page cache cleaning support Date: Mon, 30 Dec 2013 12:40:05 -0700 Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: Li Wang , Alexander Viro , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Cong Wang , Zefan Li , Matthew Wilcox On Dec 30, 2013, at 12:18, Dave Hansen wrote: >=20 > Why is this necessary to do in the kernel? Why not leave it to > userspace to walk the filesystem(s)? I would suspect that trying to do it in userspace would be quite bad. It wou= ld require traversing the whole directory tree to issue cache flushed for ea= ch subdirectory, but it doesn't know when to stop traversal. That would mean= the "cache flush" would turn into "cache pollute" and cause a lot of disk I= O for subdirectories not in cache to begin with.=20 Cheers, Andreas= -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org