From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id 45E9A6B04AC for ; Mon, 31 Jul 2017 13:21:29 -0400 (EDT) Received: by mail-qk0-f199.google.com with SMTP id k14so93787618qkl.7 for ; Mon, 31 Jul 2017 10:21:29 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id i64si11421600qtb.371.2017.07.31.10.21.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 31 Jul 2017 10:21:28 -0700 (PDT) Date: Mon, 31 Jul 2017 13:21:24 -0400 From: Jerome Glisse Subject: Re: [PATCH 09/15] mm/hmm/devmem: device memory hotplug using ZONE_DEVICE v6 Message-ID: <20170731172122.GA24626@redhat.com> References: <20170628180047.5386-1-jglisse@redhat.com> <20170628180047.5386-10-jglisse@redhat.com> <20170728111003.GA2278@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170728111003.GA2278@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, John Hubbard , Dan Williams , David Nellans , Evgeny Baskakov , Mark Hairgrove , Sherry Cheung , Subhash Gutti On Fri, Jul 28, 2017 at 01:10:03PM +0200, Michal Hocko wrote: > I haven't seen a newer version posted but the same comment applies on > your hmm-v25-4.9 git version from > git://people.freedesktop.org/~glisse/linux > > On Wed 28-06-17 14:00:41, Jerome Glisse wrote: > > This introduce a simple struct and associated helpers for device driver > > to use when hotpluging un-addressable device memory as ZONE_DEVICE. It > > will find a unuse physical address range and trigger memory hotplug for > > it which allocates and initialize struct page for the device memory. > > Please document the hotplug semantic some more please (who is in charge, > what is the lifetime, userspace API to add/remove this memory if any > etc...). > > I can see you call add_pages. Please document why arch_add_memory (like > devm_memremap_pages) is not used. You also never seem to online the > range which is in line with nvdim usage and it is OK. But then I fail to > understand why you need I added documentation in function and in commit message: https://cgit.freedesktop.org/~glisse/linux/commit/?h=hmm-next&id=33e236a64da84423c83db401fc62ea13877111f2 Not much to say i am affraid as everything is under control of the device driver (when hotplug/hotremove happens, memory management, userspace API, ...). > > [...] > > + mem_hotplug_begin(); > > + ret = add_pages(nid, align_start >> PAGE_SHIFT, > > + align_size >> PAGE_SHIFT, false); > > + if (ret) { > > + mem_hotplug_done(); > > + goto error_add_memory; > > + } > > + move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE], > > + align_start >> PAGE_SHIFT, > > + align_size >> PAGE_SHIFT); > > + mem_hotplug_done(); > > + > > + for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) { > > + struct page *page = pfn_to_page(pfn); > > + > > + /* > > + * ZONE_DEVICE pages union ->lru with a ->pgmap back > > + * pointer. It is a bug if a ZONE_DEVICE page is ever > > + * freed or placed on a driver-private list. Therefore, > > + * seed the storage with LIST_POISON* values. > > + */ > > + list_del(&page->lru); > > this? The page is not on any list yet - it hasn't been added to the page > allocator. Like comments says it was to init page->lru.next|prev with poison values it is not important so i remove it. Jerome -- 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