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[209.132.180.67]) by mx.google.com with ESMTP id e8si1038821oie.96.2020.02.05.16.15.12; Wed, 05 Feb 2020 16:15:23 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=eMDPsRAY; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727591AbgBFANa (ORCPT + 99 others); Wed, 5 Feb 2020 19:13:30 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:35912 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727149AbgBFAN3 (ORCPT ); Wed, 5 Feb 2020 19:13:29 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580948008; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gjNSHKpcN0ERcFppftZia74xuUlFNrC3nkefsHrS3V8=; b=eMDPsRAYHU+93UEAqhIJ8lYmTWYNMx7LseXkSN+hdHkFP5ND1Km0Tel8217hGjWmhRkt0d +FAkmco6cTPkHv0usfG059rQP+julK74qX0umMKZWlgGtQfWjI8OM4uqEIKiPL7+DQu7my cJes6xJMlzWW4Hh4h3ApZgwKNABUlU0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-96-FD_rIqVvP92U9i_TiHpb2w-1; Wed, 05 Feb 2020 19:13:25 -0500 X-MC-Unique: FD_rIqVvP92U9i_TiHpb2w-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E3D97801E6C; Thu, 6 Feb 2020 00:13:23 +0000 (UTC) Received: from localhost (ovpn-12-19.pek2.redhat.com [10.72.12.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 944C560BF7; Thu, 6 Feb 2020 00:13:20 +0000 (UTC) Date: Thu, 6 Feb 2020 08:13:17 +0800 From: Baoquan He To: Wei Yang Cc: David Hildenbrand , 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: <20200206001317.GH8965@MiWiFi-R3L-srv> References: <20200205135251.37488-1-david@redhat.com> <20200205231945.GB28446@richard> <20200205235007.GA28870@richard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200205235007.GA28870@richard> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. It truly has a risk that system ram is very huge to make the block size is 2G, someone try to insert a 1G memory board. However, it should only exist in experiment environment, e.g build a guest with enough ram, then hot add 1G DIMM. In reality, we don't need to worry about it, at least what I saw is 512G order of magnitude. > > > >This function says the range should be block_size aligned. And if I am > >correct, block size on x86 should be in the range > > > > [MIN_MEMORY_BLOCK_SIZE, MEM_SIZE_FOR_LARGE_BLOCK] > > > >And MIN_MEMORY_BLOCK_SIZE is section size. No, if I got it right, the range on x86 is [MIN_MEMORY_BLOCK_SIZE, MAX_BLOCK_SIZE]. MEM_SIZE_FOR_LARGE_BLOCK is the starting point from which block size can be adjusted. Otherwise it's MIN_MEMORY_BLOCK_SIZE. /* Amount of ram needed to start using large blocks */ #define MEM_SIZE_FOR_LARGE_BLOCK (64UL << 30) > > > >Seems currently we support subsection hotplug? Then how a subsection range got > >hotplug? Or this patch is a pre-requisite? The sub-section hotplug feature was added by your colleague Dan Williams. It intends to fix a nvdimms issue that nvdimms device could be mapped into a non section size aligned starting address. And nvdimms makes use of the existing memory hotplug mechanism to manage pages. Not sure if we are saying the same thing. > > > > One more question is we support hot-add subsection memory but not support > hot-online subsection memory. > > Is my understanding correct? > > -- > Wei Yang > Help you, Help me >