From: David Hildenbrand <david@redhat.com> To: Michal Hocko <mhocko@kernel.org> Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, "Michael S . Tsirkin" <mst@redhat.com>, Oscar Salvador <osalvador@suse.com>, Pavel Tatashin <pasha.tatashin@soleen.com>, Wei Yang <richard.weiyang@gmail.com>, Dan Williams <dan.j.williams@intel.com>, Qian Cai <cai@lca.pw> Subject: Re: [PATCH RFC v4 08/13] mm/memory_hotplug: Introduce offline_and_remove_memory() Date: Tue, 25 Feb 2020 15:27:28 +0100 [thread overview] Message-ID: <d1dbb687-7959-f4f1-6a64-33ee039782ef@redhat.com> (raw) In-Reply-To: <20200225141134.GU22443@dhcp22.suse.cz> On 25.02.20 15:11, Michal Hocko wrote: > On Thu 12-12-19 18:11:32, David Hildenbrand wrote: >> virtio-mem wants to offline and remove a memory block once it unplugged >> all subblocks (e.g., using alloc_contig_range()). Let's provide >> an interface to do that from a driver. virtio-mem already supports to >> offline partially unplugged memory blocks. Offlining a fully unplugged >> memory block will not require to migrate any pages. All unplugged >> subblocks are PageOffline() and have a reference count of 0 - so >> offlining code will simply skip them. >> >> All we need an interface to trigger the "offlining" and the removing in a >> single operation - to make sure the memory block cannot get onlined by >> user space again before it gets removed. > > Why does that matter? Is it really likely that the userspace would > interfere? What would be the scenario? I guess it's not that relevant after all (I think this comment dates back to the times where we didn't have try_remove_memory() and could actually BUG_ON() in remove_memory() if there would have been a race). Can drop that part. > > Or is still mostly about not requiring callers to open code this general > patter? From kernel module context, I cannot get access to the actual memory block device (find_memory_block()) and call the device_unregister(). Especially, also the device hotplug lock is not exported. So this is a clean helper function to be used from kernel module context. (e.g., also hyper-v showed interest for using that) -- Thanks, David / dhildenb
WARNING: multiple messages have this Message-ID (diff)
From: David Hildenbrand <david@redhat.com> To: Michal Hocko <mhocko@kernel.org> Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, "Michael S . Tsirkin" <mst@redhat.com>, Oscar Salvador <osalvador@suse.com>, Pavel Tatashin <pasha.tatashin@soleen.com>, Wei Yang <richard.weiyang@gmail.com>, Dan Williams <dan.j.williams@intel.com>, Qian Cai <cai@lca.pw> Subject: [virtio-dev] Re: [PATCH RFC v4 08/13] mm/memory_hotplug: Introduce offline_and_remove_memory() Date: Tue, 25 Feb 2020 15:27:28 +0100 [thread overview] Message-ID: <d1dbb687-7959-f4f1-6a64-33ee039782ef@redhat.com> (raw) In-Reply-To: <20200225141134.GU22443@dhcp22.suse.cz> On 25.02.20 15:11, Michal Hocko wrote: > On Thu 12-12-19 18:11:32, David Hildenbrand wrote: >> virtio-mem wants to offline and remove a memory block once it unplugged >> all subblocks (e.g., using alloc_contig_range()). Let's provide >> an interface to do that from a driver. virtio-mem already supports to >> offline partially unplugged memory blocks. Offlining a fully unplugged >> memory block will not require to migrate any pages. All unplugged >> subblocks are PageOffline() and have a reference count of 0 - so >> offlining code will simply skip them. >> >> All we need an interface to trigger the "offlining" and the removing in a >> single operation - to make sure the memory block cannot get onlined by >> user space again before it gets removed. > > Why does that matter? Is it really likely that the userspace would > interfere? What would be the scenario? I guess it's not that relevant after all (I think this comment dates back to the times where we didn't have try_remove_memory() and could actually BUG_ON() in remove_memory() if there would have been a race). Can drop that part. > > Or is still mostly about not requiring callers to open code this general > patter? From kernel module context, I cannot get access to the actual memory block device (find_memory_block()) and call the device_unregister(). Especially, also the device hotplug lock is not exported. So this is a clean helper function to be used from kernel module context. (e.g., also hyper-v showed interest for using that) -- Thanks, David / dhildenb --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
next prev parent reply other threads:[~2020-02-25 14:27 UTC|newest] Thread overview: 116+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-12-12 17:11 [PATCH RFC v4 00/13] virtio-mem: paravirtualized memory David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 01/13] ACPI: NUMA: export pxm_to_node David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2019-12-12 21:43 ` Rafael J. Wysocki 2019-12-13 9:41 ` David Hildenbrand 2019-12-13 9:41 ` David Hildenbrand 2019-12-13 9:41 ` [virtio-dev] " David Hildenbrand 2019-12-13 9:47 ` Rafael J. Wysocki 2019-12-13 9:47 ` Rafael J. Wysocki 2019-12-13 9:47 ` Rafael J. Wysocki 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 02/13] virtio-mem: Paravirtualized memory hotplug David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 03/13] virtio-mem: Paravirtualized memory hotunplug part 1 David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 04/13] mm: Export alloc_contig_range() / free_contig_range() David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 05/13] virtio-mem: Paravirtualized memory hotunplug part 2 David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 06/13] mm: Allow to offline unmovable PageOffline() pages via MEM_GOING_OFFLINE David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2020-02-25 18:26 ` Alexander Duyck 2020-02-25 18:26 ` [virtio-dev] " Alexander Duyck 2020-02-25 18:26 ` Alexander Duyck 2020-02-25 18:49 ` David Hildenbrand 2020-02-25 18:49 ` [virtio-dev] " David Hildenbrand 2020-02-25 18:49 ` David Hildenbrand 2020-02-25 21:46 ` Alexander Duyck 2020-02-25 21:46 ` [virtio-dev] " Alexander Duyck 2020-02-25 21:46 ` Alexander Duyck 2020-02-25 22:19 ` David Hildenbrand 2020-02-25 22:19 ` [virtio-dev] " David Hildenbrand 2020-02-25 22:19 ` David Hildenbrand 2020-02-26 16:27 ` Alexander Duyck 2020-02-26 16:27 ` [virtio-dev] " Alexander Duyck 2020-02-26 16:27 ` Alexander Duyck 2019-12-12 17:11 ` [PATCH RFC v4 07/13] virtio-mem: Allow to offline partially unplugged memory blocks David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 08/13] mm/memory_hotplug: Introduce offline_and_remove_memory() David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2020-02-25 14:11 ` Michal Hocko 2020-02-25 14:27 ` David Hildenbrand [this message] 2020-02-25 14:27 ` [virtio-dev] " David Hildenbrand 2020-03-02 12:48 ` Michal Hocko 2020-03-02 12:53 ` David Hildenbrand 2020-03-02 12:53 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 09/13] virtio-mem: Offline and remove completely unplugged memory blocks David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 10/13] virtio-mem: Better retry handling David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 11/13] mm/vmscan: Move count_vm_event(DROP_SLAB) into drop_slab() David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2020-02-25 14:13 ` Michal Hocko 2019-12-12 17:11 ` [PATCH RFC v4 12/13] mm/vmscan: Export drop_slab() and drop_slab_node() David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2020-02-25 14:58 ` Michal Hocko 2020-02-25 15:09 ` David Hildenbrand 2020-02-25 15:09 ` [virtio-dev] " David Hildenbrand 2020-02-25 17:06 ` Michal Hocko 2020-02-25 17:23 ` David Hildenbrand 2020-02-25 17:23 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-12 17:11 ` [PATCH RFC v4 13/13] virtio-mem: Drop slab objects when unplug continues to fail David Hildenbrand 2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand 2019-12-12 17:11 ` David Hildenbrand 2019-12-13 20:15 ` [PATCH RFC v4 00/13] virtio-mem: paravirtualized memory Konrad Rzeszutek Wilk 2019-12-13 20:15 ` Konrad Rzeszutek Wilk 2019-12-16 11:03 ` David Hildenbrand 2019-12-16 11:03 ` David Hildenbrand 2019-12-16 11:03 ` [virtio-dev] " David Hildenbrand 2019-12-24 6:58 ` teawater 2019-12-24 9:28 ` David Hildenbrand 2019-12-24 9:28 ` [virtio-dev] " David Hildenbrand 2019-12-24 9:28 ` David Hildenbrand 2020-01-09 13:48 ` David Hildenbrand 2020-01-09 13:48 ` [virtio-dev] " David Hildenbrand 2020-01-29 9:41 ` David Hildenbrand 2020-01-29 9:41 ` [virtio-dev] " David Hildenbrand 2020-01-29 9:41 ` David Hildenbrand 2020-02-25 9:58 ` David Hildenbrand 2020-02-25 9:58 ` [virtio-dev] " David Hildenbrand 2020-02-25 9:58 ` David Hildenbrand 2020-06-05 8:55 ` Alex Shi 2020-06-05 8:55 ` Alex Shi 2020-06-05 9:08 ` David Hildenbrand 2020-06-05 9:08 ` [virtio-dev] " David Hildenbrand 2020-06-05 9:08 ` David Hildenbrand 2020-06-05 9:36 ` David Hildenbrand 2020-06-05 9:36 ` [virtio-dev] " David Hildenbrand 2020-06-05 9:36 ` David Hildenbrand 2020-06-05 10:05 ` David Hildenbrand 2020-06-05 10:05 ` [virtio-dev] " David Hildenbrand 2020-06-05 10:05 ` David Hildenbrand 2020-06-05 10:46 ` Alex Shi 2020-06-05 10:46 ` Alex Shi 2020-06-05 12:18 ` David Hildenbrand 2020-06-05 12:18 ` [virtio-dev] " David Hildenbrand 2020-06-05 12:18 ` David Hildenbrand 2020-06-09 3:05 ` Alex Shi 2020-06-09 3:05 ` Alex Shi 2020-06-05 10:08 ` Alex Shi 2020-06-05 10:08 ` Alex Shi 2020-06-05 10:06 ` Alex Shi 2020-06-05 10:06 ` Alex Shi 2020-01-09 13:48 ` David Hildenbrand
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