From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from g4t3427.houston.hpe.com (g4t3427.houston.hpe.com [15.241.140.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 90D532095A6CD for ; Thu, 29 Jun 2017 14:15:13 -0700 (PDT) Subject: Re: [PATCH v4 12/16] libnvdimm, nfit: enable support for volatile ranges References: <149875877608.10031.17813337234536358002.stgit@dwillia2-desk3.amr.corp.intel.com> <149875884190.10031.6179599135820559644.stgit@dwillia2-desk3.amr.corp.intel.com> <595552F5.5040008@hpe.com> From: Linda Knippers Message-ID: <59556E37.80808@hpe.com> Date: Thu, 29 Jun 2017 17:16:39 -0400 MIME-Version: 1.0 In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Dan Williams Cc: Jan Kara , Matthew Wilcox , X86 ML , "linux-kernel@vger.kernel.org" , "linux-nvdimm@lists.01.org" , Al Viro , linux-fsdevel , Christoph Hellwig List-ID: On 06/29/2017 04:42 PM, Dan Williams wrote: > On Thu, Jun 29, 2017 at 12:20 PM, Linda Knippers wrote: >> On 06/29/2017 01:54 PM, Dan Williams wrote: >>> Allow volatile nfit ranges to participate in all the same infrastructure >>> provided for persistent memory regions. >> >> This seems to be a bit more than "other rework". > > It's part of the rationale for having a "write_cache" control > attribute. There's only so much I can squeeze into the subject line, > but it is mentioned in the cover letter. > >>> A resulting resulting namespace >>> device will still be called "pmem", but the parent region type will be >>> "nd_volatile". >> >> What does this look like to a user or admin? How does someone know that >> /dev/pmemX is persistent memory and /dev/pmemY isn't? Someone shouldn't >> have to weed through /sys or ndctl some other interface to figure that out >> in the future if they don't have to do that today. We have different >> names for BTT namespaces. Is there a different name for volatile ranges? > > No, the block device name is still /dev/pmem. It's already the case > that you need to check behind just the name of the device to figure > out if something is actually volatile or not (see memmap=ss!nn > configurations), I don't have any experience with using memmap but if it's primarily used by developers without NVDIMMs, they'd know it's not persistent. Or is it primarily used by administrators using non-NFIT NVDIMMs, in which case it is persistent? In any case, how exactly does one determine whether the device is volatile or not? I'm dumb so tell me the command line or API. > so I would not be in favor of changing the device > name if we think the memory might not be persistent. Moreover, I think > it was a mistake that we change the device name for btt or not, and > I'm glad Matthew talked me out of making the same mistake with > memory-mode vs raw-mode pmem namespaces. So, the block device name > just reflects the driver of the block device, not the properties of > the device, just like all other block device instances. I agree that creating a new device name for BTT was perhaps a mistake, although it would be good to know how to query a device property for sector atomicity. The difference between BTT vs. non-BTT seems less critical to me than knowing in an obvious way whether the device is actually persistent. -- ljk _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753458AbdF2VQv (ORCPT ); Thu, 29 Jun 2017 17:16:51 -0400 Received: from g9t1613g.houston.hpe.com ([15.241.32.99]:34839 "EHLO g9t1613g.houston.hpe.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751752AbdF2VQr (ORCPT ); Thu, 29 Jun 2017 17:16:47 -0400 Authentication-Results: hpe.com; dkim=none (message not signed) header.d=none;hpe.com; dmarc=none action=none header.from=hpe.com; Subject: Re: [PATCH v4 12/16] libnvdimm, nfit: enable support for volatile ranges To: Dan Williams References: <149875877608.10031.17813337234536358002.stgit@dwillia2-desk3.amr.corp.intel.com> <149875884190.10031.6179599135820559644.stgit@dwillia2-desk3.amr.corp.intel.com> <595552F5.5040008@hpe.com> CC: "linux-nvdimm@lists.01.org" , Jan Kara , Matthew Wilcox , X86 ML , "linux-kernel@vger.kernel.org" , Al Viro , linux-fsdevel , Christoph Hellwig From: Linda Knippers Message-ID: <59556E37.80808@hpe.com> Date: Thu, 29 Jun 2017 17:16:39 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [73.60.235.182] X-ClientProxiedBy: CY4PR01CA0008.prod.exchangelabs.com (10.169.249.18) To TU4PR84MB0078.NAMPRD84.PROD.OUTLOOK.COM (10.162.186.156) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 512592cd-a893-45d3-c869-08d4bf34247c X-MS-Office365-Filtering-HT: Tenant X-Microsoft-Antispam: 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X-MS-Exchange-Transport-CrossTenantHeadersStamped: TU4PR84MB0078 X-OriginatorOrg: hpe.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/29/2017 04:42 PM, Dan Williams wrote: > On Thu, Jun 29, 2017 at 12:20 PM, Linda Knippers wrote: >> On 06/29/2017 01:54 PM, Dan Williams wrote: >>> Allow volatile nfit ranges to participate in all the same infrastructure >>> provided for persistent memory regions. >> >> This seems to be a bit more than "other rework". > > It's part of the rationale for having a "write_cache" control > attribute. There's only so much I can squeeze into the subject line, > but it is mentioned in the cover letter. > >>> A resulting resulting namespace >>> device will still be called "pmem", but the parent region type will be >>> "nd_volatile". >> >> What does this look like to a user or admin? How does someone know that >> /dev/pmemX is persistent memory and /dev/pmemY isn't? Someone shouldn't >> have to weed through /sys or ndctl some other interface to figure that out >> in the future if they don't have to do that today. We have different >> names for BTT namespaces. Is there a different name for volatile ranges? > > No, the block device name is still /dev/pmem. It's already the case > that you need to check behind just the name of the device to figure > out if something is actually volatile or not (see memmap=ss!nn > configurations), I don't have any experience with using memmap but if it's primarily used by developers without NVDIMMs, they'd know it's not persistent. Or is it primarily used by administrators using non-NFIT NVDIMMs, in which case it is persistent? In any case, how exactly does one determine whether the device is volatile or not? I'm dumb so tell me the command line or API. > so I would not be in favor of changing the device > name if we think the memory might not be persistent. Moreover, I think > it was a mistake that we change the device name for btt or not, and > I'm glad Matthew talked me out of making the same mistake with > memory-mode vs raw-mode pmem namespaces. So, the block device name > just reflects the driver of the block device, not the properties of > the device, just like all other block device instances. I agree that creating a new device name for BTT was perhaps a mistake, although it would be good to know how to query a device property for sector atomicity. The difference between BTT vs. non-BTT seems less critical to me than knowing in an obvious way whether the device is actually persistent. -- ljk