From: Wei Yang <richard.weiyang@linux.alibaba.com>
To: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
virtualization@lists.linux-foundation.org,
Andrew Morton <akpm@linux-foundation.org>,
"Michael S . Tsirkin" <mst@redhat.com>,
Jason Wang <jasowang@redhat.com>,
Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Subject: Re: [PATCH v1 13/29] virtio-mem: factor out handling of fake-offline pages in memory notifier
Date: Fri, 16 Oct 2020 16:00:46 +0800 [thread overview]
Message-ID: <20201016080046.GA43862@L-31X9LVDL-1304.local> (raw)
In-Reply-To: <20201016071502.GM86495@L-31X9LVDL-1304.local>
On Fri, Oct 16, 2020 at 03:15:03PM +0800, Wei Yang wrote:
>On Mon, Oct 12, 2020 at 02:53:07PM +0200, David Hildenbrand wrote:
>>Let's factor out the core pieces and place the implementation next to
>>virtio_mem_fake_offline(). We'll reuse this functionality soon.
>>
>>Cc: "Michael S. Tsirkin" <mst@redhat.com>
>>Cc: Jason Wang <jasowang@redhat.com>
>>Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>>Signed-off-by: David Hildenbrand <david@redhat.com>
>>---
>> drivers/virtio/virtio_mem.c | 73 +++++++++++++++++++++++++------------
>> 1 file changed, 50 insertions(+), 23 deletions(-)
>>
>>diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
>>index d132bc54ef57..a2124892e510 100644
>>--- a/drivers/virtio/virtio_mem.c
>>+++ b/drivers/virtio/virtio_mem.c
>>@@ -168,6 +168,10 @@ static LIST_HEAD(virtio_mem_devices);
>>
>> static void virtio_mem_online_page_cb(struct page *page, unsigned int order);
>> static void virtio_mem_retry(struct virtio_mem *vm);
>>+static void virtio_mem_fake_offline_going_offline(unsigned long pfn,
>>+ unsigned long nr_pages);
>>+static void virtio_mem_fake_offline_cancel_offline(unsigned long pfn,
>>+ unsigned long nr_pages);
>>
>> /*
>> * Register a virtio-mem device so it will be considered for the online_page
>>@@ -604,27 +608,15 @@ static void virtio_mem_notify_going_offline(struct virtio_mem *vm,
>> unsigned long mb_id)
>> {
>> const unsigned long nr_pages = PFN_DOWN(vm->subblock_size);
>>- struct page *page;
>> unsigned long pfn;
>>- int sb_id, i;
>>+ int sb_id;
>>
>> for (sb_id = 0; sb_id < vm->nb_sb_per_mb; sb_id++) {
>> if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
>> continue;
>>- /*
>>- * Drop our reference to the pages so the memory can get
>>- * offlined and add the unplugged pages to the managed
>>- * page counters (so offlining code can correctly subtract
>>- * them again).
>>- */
>> pfn = PFN_DOWN(virtio_mem_mb_id_to_phys(mb_id) +
>> sb_id * vm->subblock_size);
>>- adjust_managed_page_count(pfn_to_page(pfn), nr_pages);
>
>One question about the original code, why we want to adjust count here?
>
>The code flow is
>
> __offline_pages()
> memory_notify(MEM_GOING_OFFLINE, &arg)
> virtio_mem_notify_going_offline(vm, mb_id)
> adjust_managed_page_count(pfn_to_page(pfn), nr_pages)
> adjust_managed_page_count(pfn_to_page(start_pfn), -offlined_pages)
>
>Do we adjust the count twice?
>
Ah, I got the reason why we need to adjust count for *unplugged* sub-blocks.
>>- for (i = 0; i < nr_pages; i++) {
>>- page = pfn_to_page(pfn + i);
>>- if (WARN_ON(!page_ref_dec_and_test(page)))
Another question is when we grab a refcount for the unpluged pages? The one
you mentioned in virtio_mem_set_fake_offline().
>>- dump_page(page, "unplugged page referenced");
>>- }
>>+ virtio_mem_fake_offline_going_offline(pfn, nr_pages);
>> }
>> }
>>
>>@@ -633,21 +625,14 @@ static void virtio_mem_notify_cancel_offline(struct virtio_mem *vm,
>> {
>> const unsigned long nr_pages = PFN_DOWN(vm->subblock_size);
>> unsigned long pfn;
>>- int sb_id, i;
>>+ int sb_id;
>>
>> for (sb_id = 0; sb_id < vm->nb_sb_per_mb; sb_id++) {
>> if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
>> continue;
>>- /*
>>- * Get the reference we dropped when going offline and
>>- * subtract the unplugged pages from the managed page
>>- * counters.
>>- */
>> pfn = PFN_DOWN(virtio_mem_mb_id_to_phys(mb_id) +
>> sb_id * vm->subblock_size);
>>- adjust_managed_page_count(pfn_to_page(pfn), -nr_pages);
>>- for (i = 0; i < nr_pages; i++)
>>- page_ref_inc(pfn_to_page(pfn + i));
>>+ virtio_mem_fake_offline_cancel_offline(pfn, nr_pages);
>> }
>> }
>>
>>@@ -853,6 +838,48 @@ static int virtio_mem_fake_offline(unsigned long pfn, unsigned long nr_pages)
>> return 0;
>> }
>>
>>+/*
>>+ * Handle fake-offline pages when memory is going offline - such that the
>>+ * pages can be skipped by mm-core when offlining.
>>+ */
>>+static void virtio_mem_fake_offline_going_offline(unsigned long pfn,
>>+ unsigned long nr_pages)
>>+{
>>+ struct page *page;
>>+ unsigned long i;
>>+
>>+ /*
>>+ * Drop our reference to the pages so the memory can get offlined
>>+ * and add the unplugged pages to the managed page counters (so
>>+ * offlining code can correctly subtract them again).
>>+ */
>>+ adjust_managed_page_count(pfn_to_page(pfn), nr_pages);
>>+ /* Drop our reference to the pages so the memory can get offlined. */
>>+ for (i = 0; i < nr_pages; i++) {
>>+ page = pfn_to_page(pfn + i);
>>+ if (WARN_ON(!page_ref_dec_and_test(page)))
>>+ dump_page(page, "fake-offline page referenced");
>>+ }
>>+}
>>+
>>+/*
>>+ * Handle fake-offline pages when memory offlining is canceled - to undo
>>+ * what we did in virtio_mem_fake_offline_going_offline().
>>+ */
>>+static void virtio_mem_fake_offline_cancel_offline(unsigned long pfn,
>>+ unsigned long nr_pages)
>>+{
>>+ unsigned long i;
>>+
>>+ /*
>>+ * Get the reference we dropped when going offline and subtract the
>>+ * unplugged pages from the managed page counters.
>>+ */
>>+ adjust_managed_page_count(pfn_to_page(pfn), -nr_pages);
>>+ for (i = 0; i < nr_pages; i++)
>>+ page_ref_inc(pfn_to_page(pfn + i));
>>+}
>>+
>> static void virtio_mem_online_page_cb(struct page *page, unsigned int order)
>> {
>> const unsigned long addr = page_to_phys(page);
>>--
>>2.26.2
>
>--
>Wei Yang
>Help you, Help me
--
Wei Yang
Help you, Help me
next prev parent reply other threads:[~2020-10-16 8:00 UTC|newest]
Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-12 12:52 [PATCH v1 00/29] virtio-mem: Big Block Mode (BBM) David Hildenbrand
2020-10-12 12:52 ` [PATCH v1 01/29] virtio-mem: determine nid only once using memory_add_physaddr_to_nid() David Hildenbrand
2020-10-15 3:56 ` Wei Yang
2020-10-15 19:26 ` Pankaj Gupta
2020-10-12 12:52 ` [PATCH v1 02/29] virtio-mem: simplify calculation in virtio_mem_mb_state_prepare_next_mb() David Hildenbrand
2020-10-15 4:02 ` Wei Yang
2020-10-15 8:00 ` David Hildenbrand
2020-10-15 10:00 ` Wei Yang
2020-10-15 10:01 ` David Hildenbrand
2020-10-15 20:24 ` Pankaj Gupta
2020-10-16 9:00 ` David Hildenbrand
2020-10-12 12:52 ` [PATCH v1 03/29] virtio-mem: simplify MAX_ORDER - 1 / pageblock_order handling David Hildenbrand
2020-10-15 7:06 ` Wei Yang
2020-10-12 12:52 ` [PATCH v1 04/29] virtio-mem: drop rc2 in virtio_mem_mb_plug_and_add() David Hildenbrand
2020-10-12 13:09 ` Pankaj Gupta
2020-10-15 7:14 ` Wei Yang
2020-10-12 12:52 ` [PATCH v1 05/29] virtio-mem: generalize check for added memory David Hildenbrand
2020-10-15 8:28 ` Wei Yang
2020-10-15 8:50 ` David Hildenbrand
2020-10-16 2:16 ` Wei Yang
2020-10-16 9:11 ` David Hildenbrand
2020-10-16 10:02 ` Wei Yang
2020-10-16 10:32 ` David Hildenbrand
2020-10-16 22:38 ` Wei Yang
2020-10-17 7:39 ` David Hildenbrand
2020-10-18 12:27 ` Wei Yang
2020-10-16 22:39 ` Wei Yang
2020-10-12 12:53 ` [PATCH v1 06/29] virtio-mem: generalize virtio_mem_owned_mb() David Hildenbrand
2020-10-15 8:32 ` Wei Yang
2020-10-15 8:37 ` David Hildenbrand
2020-10-15 20:30 ` Pankaj Gupta
2020-10-12 12:53 ` [PATCH v1 07/29] virtio-mem: generalize virtio_mem_overlaps_range() David Hildenbrand
2020-10-20 9:22 ` Pankaj Gupta
2020-10-12 12:53 ` [PATCH v1 08/29] virtio-mem: drop last_mb_id David Hildenbrand
2020-10-15 8:35 ` Wei Yang
2020-10-15 20:32 ` Pankaj Gupta
2020-10-12 12:53 ` [PATCH v1 09/29] virtio-mem: don't always trigger the workqueue when offlining memory David Hildenbrand
2020-10-16 4:03 ` Wei Yang
2020-10-16 9:18 ` David Hildenbrand
2020-10-18 3:57 ` Wei Yang
2020-10-19 9:04 ` David Hildenbrand
2020-10-20 0:41 ` Wei Yang
2020-10-20 9:09 ` David Hildenbrand
2020-10-12 12:53 ` [PATCH v1 10/29] virtio-mem: generalize handling when memory is getting onlined deferred David Hildenbrand
2020-10-12 12:53 ` [PATCH v1 11/29] virtio-mem: use "unsigned long" for nr_pages when fake onlining/offlining David Hildenbrand
2020-10-15 20:31 ` Pankaj Gupta
2020-10-16 6:11 ` Wei Yang
2020-10-12 12:53 ` [PATCH v1 12/29] virtio-mem: factor out fake-offlining into virtio_mem_fake_offline() David Hildenbrand
2020-10-16 6:24 ` Wei Yang
2020-10-20 9:31 ` Pankaj Gupta
2020-10-12 12:53 ` [PATCH v1 13/29] virtio-mem: factor out handling of fake-offline pages in memory notifier David Hildenbrand
2020-10-16 7:15 ` Wei Yang
2020-10-16 8:00 ` Wei Yang [this message]
2020-10-16 8:57 ` David Hildenbrand
2020-10-18 12:37 ` Wei Yang
2020-10-18 12:38 ` Wei Yang
2020-10-12 12:53 ` [PATCH v1 14/29] virtio-mem: retry fake-offlining via alloc_contig_range() on ZONE_MOVABLE David Hildenbrand
2020-10-12 12:53 ` [PATCH v1 15/29] virito-mem: document Sub Block Mode (SBM) David Hildenbrand
2020-10-15 9:33 ` David Hildenbrand
2020-10-20 9:38 ` Pankaj Gupta
2020-10-16 8:03 ` Wei Yang
2020-10-12 12:53 ` [PATCH v1 16/29] virtio-mem: memory block states are specific to " David Hildenbrand
2020-10-16 8:40 ` Wei Yang
2020-10-16 8:43 ` Wei Yang
2020-10-20 9:48 ` Pankaj Gupta
2020-10-12 12:53 ` [PATCH v1 17/29] virito-mem: subblock " David Hildenbrand
2020-10-16 8:43 ` Wei Yang
2020-10-20 9:54 ` Pankaj Gupta
2020-10-12 12:53 ` [PATCH v1 18/29] virtio-mem: factor out calculation of the bit number within the sb_states bitmap David Hildenbrand
2020-10-16 8:46 ` Wei Yang
2020-10-20 9:58 ` Pankaj Gupta
2020-10-12 12:53 ` [PATCH v1 19/29] virito-mem: existing (un)plug functions are specific to Sub Block Mode (SBM) David Hildenbrand
2020-10-16 8:49 ` Wei Yang
2020-10-12 12:53 ` [PATCH v1 20/29] virtio-mem: nb_sb_per_mb and subblock_size " David Hildenbrand
2020-10-16 8:51 ` Wei Yang
2020-10-16 8:53 ` Wei Yang
2020-10-16 13:17 ` David Hildenbrand
2020-10-18 12:41 ` Wei Yang
2020-10-19 11:57 ` David Hildenbrand
2020-10-12 12:53 ` [PATCH v1 21/29] virtio-mem: memory notifier callbacks " David Hildenbrand
2020-10-19 1:57 ` Wei Yang
2020-10-19 10:22 ` David Hildenbrand
2020-10-12 12:53 ` [PATCH v1 22/29] virtio-mem: memory block ids " David Hildenbrand
2020-10-16 8:54 ` Wei Yang
2020-10-12 12:53 ` [PATCH v1 23/29] virtio-mem: factor out adding/removing memory from Linux David Hildenbrand
2020-10-16 8:59 ` Wei Yang
2020-10-12 12:53 ` [PATCH v1 24/29] virtio-mem: print debug messages from virtio_mem_send_*_request() David Hildenbrand
2020-10-16 9:07 ` Wei Yang
2020-10-12 12:53 ` [PATCH v1 25/29] virtio-mem: Big Block Mode (BBM) memory hotplug David Hildenbrand
2020-10-16 9:38 ` Wei Yang
2020-10-16 13:13 ` David Hildenbrand
2020-10-19 2:26 ` Wei Yang
2020-10-19 9:15 ` David Hildenbrand
2020-10-12 12:53 ` [PATCH v1 26/29] virtio-mem: allow to force Big Block Mode (BBM) and set the big block size David Hildenbrand
2020-10-12 12:53 ` [PATCH v1 27/29] mm/memory_hotplug: extend offline_and_remove_memory() to handle more than one memory block David Hildenbrand
2020-10-15 13:08 ` Michael S. Tsirkin
2020-10-19 3:22 ` Wei Yang
2020-10-12 12:53 ` [PATCH v1 28/29] virtio-mem: Big Block Mode (BBM) - basic memory hotunplug David Hildenbrand
2020-10-19 3:48 ` Wei Yang
2020-10-19 9:12 ` David Hildenbrand
2020-10-12 12:53 ` [PATCH v1 29/29] virtio-mem: Big Block Mode (BBM) - safe " David Hildenbrand
2020-10-19 7:54 ` Wei Yang
2020-10-19 8:50 ` David Hildenbrand
2020-10-20 0:23 ` Wei Yang
2020-10-20 0:24 ` Wei Yang
2020-10-18 12:49 ` [PATCH v1 00/29] virtio-mem: Big Block Mode (BBM) Wei Yang
2020-10-18 15:29 ` Michael S. Tsirkin
2020-10-18 16:34 ` David Hildenbrand
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