From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yh0-f53.google.com (mail-yh0-f53.google.com [209.85.213.53]) by kanga.kvack.org (Postfix) with ESMTP id A00C86B0038 for ; Tue, 30 Sep 2014 15:33:11 -0400 (EDT) Received: by mail-yh0-f53.google.com with SMTP id b6so1318123yha.12 for ; Tue, 30 Sep 2014 12:33:11 -0700 (PDT) Received: from g4t3427.houston.hp.com (g4t3427.houston.hp.com. [15.201.208.55]) by mx.google.com with ESMTPS id 67si8313625yhi.4.2014.09.30.12.33.10 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 30 Sep 2014 12:33:11 -0700 (PDT) From: "Zuckerman, Boris" Subject: RE: [PATCH v11 00/21] Add support for NV-DIMMs to ext4 Date: Tue, 30 Sep 2014 19:31:55 +0000 Message-ID: <4C30833E5CDF444D84D942543DF65BDA6E047CAE@G4W3303.americas.hpqcorp.net> References: <1411677218-29146-1-git-send-email-matthew.r.wilcox@intel.com> <15705.1412070301@turing-police.cc.vt.edu> <20140930144854.GA5098@wil.cx> <123795.1412088827@turing-police.cc.vt.edu> <20140930160841.GB5098@wil.cx> <4C30833E5CDF444D84D942543DF65BDA6E047B9B@G4W3303.americas.hpqcorp.net> <20140930192428.GF5098@wil.cx> In-Reply-To: <20140930192428.GF5098@wil.cx> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: "Valdis.Kletnieks@vt.edu" , Matthew Wilcox , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" I am trying to refocus this thread from a particular issue to more generic = needs... Regards, Boris > -----Original Message----- > From: Matthew Wilcox [mailto:willy@linux.intel.com] > Sent: Tuesday, September 30, 2014 3:24 PM > To: Zuckerman, Boris > Cc: Matthew Wilcox; Valdis.Kletnieks@vt.edu; Matthew Wilcox; linux- > fsdevel@vger.kernel.org; linux-mm@kvack.org; linux-kernel@vger.kernel.org > Subject: Re: [PATCH v11 00/21] Add support for NV-DIMMs to ext4 >=20 > On Tue, Sep 30, 2014 at 05:10:26PM +0000, Zuckerman, Boris wrote: > > > > > > The more I think about this, the more I think this is a bad idea. > > > When you have a file open with O_DIRECT, your I/O has to be done in > > > 512-byte multiples, and it has to be aligned to 512-byte boundaries > > > in memory. If an unsuspecting application has O_DIRECT forced on > > > it, it isn't going to know to do that, and so all its I/Os will fail. > > > It'll also be horribly inefficient if a program has the file mmaped. > > > > > > What problem are you really trying to solve? Some big files hogging = the page > cache? > > > -- > > > > Page cache? As another copy in RAM? > > NV_DIMMs may be viewed as a caching device. This caching can be impleme= nted on > the level of NV block/offset or may have some hints from FS and applicati= ons. > Temporary files is one example. They may not need to hit NV domain ever. = Some > transactional journals or DB files is another example. They may stay in R= AM until power > off. >=20 > Boris, you're confused. Valdis is trying to solve an unrelated problem (= and hopes my > DAX patches will do it for him). I'm explaining to him why what he wants= to do is a bad > idea. This tangent is unrelated to NV-DIMMs. -- 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