From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE2B8C352A2 for ; Thu, 6 Feb 2020 11:38:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7BB2320659 for ; Thu, 6 Feb 2020 11:38:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7BB2320659 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 039FA6B0003; Thu, 6 Feb 2020 06:38:01 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id F2BDF6B0006; Thu, 6 Feb 2020 06:38:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E1BC36B0007; Thu, 6 Feb 2020 06:38:00 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0237.hostedemail.com [216.40.44.237]) by kanga.kvack.org (Postfix) with ESMTP id C7B816B0003 for ; Thu, 6 Feb 2020 06:38:00 -0500 (EST) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 6411C180AD802 for ; Thu, 6 Feb 2020 11:38:00 +0000 (UTC) X-FDA: 76459503120.25.stone82_b9876c939531 X-HE-Tag: stone82_b9876c939531 X-Filterd-Recvd-Size: 5541 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Thu, 6 Feb 2020 11:37:59 +0000 (UTC) X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Feb 2020 03:37:58 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,409,1574150400"; d="scan'208";a="264572935" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga002.fm.intel.com with ESMTP; 06 Feb 2020 03:37:56 -0800 Date: Thu, 6 Feb 2020 19:38:12 +0800 From: Wei Yang To: David Hildenbrand Cc: Baoquan He , Wei Yang , Wei Yang , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Segher Boessenkool , Andrew Morton , Michal Hocko , Oscar Salvador Subject: Re: [PATCH v1] mm/memory_hotplug: Easier calculation to get pages to next section boundary Message-ID: <20200206113812.GA7092@richard> Reply-To: Wei Yang References: <20200205135251.37488-1-david@redhat.com> <20200205231945.GB28446@richard> <20200205235007.GA28870@richard> <20200206001317.GH8965@MiWiFi-R3L-srv> <20200206003736.GI8965@MiWiFi-R3L-srv> <20200206022644.6u7pxf7by2w5trmi@master> <20200206024816.GK8965@MiWiFi-R3L-srv> <20200206043401.22i2cucwqctsrtps@master> <20200206043924.GM8965@MiWiFi-R3L-srv> <14cca79e-2e76-28ef-1a17-81f044548c33@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <14cca79e-2e76-28ef-1a17-81f044548c33@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Feb 06, 2020 at 10:01:21AM +0100, David Hildenbrand wrote: >On 06.02.20 05:39, Baoquan He wrote: >> On 02/06/20 at 04:34am, Wei Yang wrote: >>> On Thu, Feb 06, 2020 at 10:48:16AM +0800, Baoquan He wrote: >>>> On 02/06/20 at 02:26am, Wei Yang wrote: >>>>> On Thu, Feb 06, 2020 at 08:37:36AM +0800, Baoquan He wrote: >>>>>> On 02/06/20 at 08:13am, Baoquan He wrote: >>>>>>> On 02/06/20 at 07:50am, Wei Yang wrote: >>>>>>>> On Thu, Feb 06, 2020 at 07:19:45AM +0800, Wei Yang wrote: >>>>>>>>> On Wed, Feb 05, 2020 at 02:52:51PM +0100, David Hildenbrand wrote: >>>>>>>>>> Let's use a calculation that's easier to understand and calculates the >>>>>>>>>> same result. Reusing existing macros makes this look nicer. >>>>>>>>>> >>>>>>>>>> We always want to have the number of pages (> 0) to the next section >>>>>>>>>> boundary, starting from the current pfn. >>>>>>>>>> >>>>>>>>>> Suggested-by: Segher Boessenkool >>>>>>>>>> Cc: Andrew Morton >>>>>>>>>> Cc: Michal Hocko >>>>>>>>>> Cc: Oscar Salvador >>>>>>>>>> Cc: Baoquan He >>>>>>>>>> Cc: Wei Yang >>>>>>>>>> Signed-off-by: David Hildenbrand >>>>>>>>> >>>>>>>>> Reviewed-by: Wei Yang >>>>>>>>> >>>>>>>>> BTW, I got one question about hotplug size requirement. >>>>>>>>> >>>>>>>>> I thought the hotplug range should be section size aligned, while taking a >>>>>>>>> look into current code function check_hotplug_memory_range() guard the range. >>>>>>> >>>>>>> A good question. The current code should be block size aligned. I >>>>>>> remember in some places we assume each block comprise all the sections. >>>>>>> Can't imagine one or some of them are half section filled. >>>>>> >>>>>> I could be wrong, half filled block may not cause problem. >>>>>> >>>>> >>>>> David must be angry about our flooding the mail list :-) >>>> >>>> Believe he won't, :-) If you like, we can talk off line. >>>> >>>>> >>>>> Check the code again, there are two memory range check: >>>>> >>>>> * check_hotplug_memory_range(), block/section aligned >>>>> * check_pfn_span(), subsection aligned >>>>> >>>>> The second check, check_pfn_span() in __add_pages(), enable the capability to >>>>> add a memory range with subsection size. >>>>> >>>>> This means hotplug still keeps section alignment. >>>> >>>> memremap_pages() also call add_pages(), it doesn't have the >>>> check_hotplug_memory_range() invocation. check_pfn_span() is made for >>>> it specifically. >>>> >>> >>> If my understanding is correct, memremap_pages() is used to add some dev >>> memory to system. This is the use case which Dan want to enable for >>> sub-section. Since memremap_pages() is not called in mem-hotplug path, this >>> doesn't affect the hotplug range alignment. >> >> Yeah, we are on the same page. > >We allow sub-section hoy-add only for device memory/hmm. BIOS often >align PMEM devices to sub-sections, and not supporting this makes life >difficult to support these devices. (You cannot simply cut off something >of a disk :) ) > >System memory can only be hotplugged in memory block granularity, the >same granularity onlining/offlining from user space will happen. Boot >memory, however, can be sub-section aligned, but can never be offlined >(as it contains holes) and therefore never be removed. > This makes life easier. Thanks for your explanation. -- Wei Yang Help you, Help me