From: Wei Wang <wei.w.wang@intel.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
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Subject: Re: [PATCH v12 6/8] mm: support reporting free page blocks
Date: Wed, 26 Jul 2017 19:44:23 +0800 [thread overview]
Message-ID: <59788097.6010402@intel.com> (raw)
In-Reply-To: <20170726102458.GH2981@dhcp22.suse.cz>
On 07/26/2017 06:24 PM, Michal Hocko wrote:
> On Wed 26-07-17 10:22:23, Wei Wang wrote:
>> On 07/25/2017 10:53 PM, Michal Hocko wrote:
>>> On Tue 25-07-17 14:47:16, Wang, Wei W wrote:
>>>> On Tuesday, July 25, 2017 8:42 PM, hal Hocko wrote:
>>>>> On Tue 25-07-17 19:56:24, Wei Wang wrote:
>>>>>> On 07/25/2017 07:25 PM, Michal Hocko wrote:
>>>>>>> On Tue 25-07-17 17:32:00, Wei Wang wrote:
>>>>>>>> On 07/24/2017 05:00 PM, Michal Hocko wrote:
>>>>>>>>> On Wed 19-07-17 20:01:18, Wei Wang wrote:
>>>>>>>>>> On 07/19/2017 04:13 PM, Michal Hocko wrote:
>>>>>>>>> [...
>>>>>> We don't need to do the pfn walk in the guest kernel. When the API
>>>>>> reports, for example, a 2MB free page block, the API caller offers to
>>>>>> the hypervisor the base address of the page block, and size=2MB, to
>>>>>> the hypervisor.
>>>>> So you want to skip pfn walks by regularly calling into the page allocator to
>>>>> update your bitmap. If that is the case then would an API that would allow you
>>>>> to update your bitmap via a callback be s sufficient? Something like
>>>>> void walk_free_mem(int node, int min_order,
>>>>> void (*visit)(unsigned long pfn, unsigned long nr_pages))
>>>>>
>>>>> The function will call the given callback for each free memory block on the given
>>>>> node starting from the given min_order. The callback will be strictly an atomic
>>>>> and very light context. You can update your bitmap from there.
>>>> I would need to introduce more about the background here:
>>>> The hypervisor and the guest live in their own address space. The hypervisor's bitmap
>>>> isn't seen by the guest. I think we also wouldn't be able to give a callback function
>>> >from the hypervisor to the guest in this case.
>>> How did you plan to use your original API which export struct page array
>>> then?
>>
>> That's where the virtio-balloon driver comes in. It uses a shared ring
>> mechanism to
>> send the guest memory info to the hypervisor.
>>
>> We didn't expose the struct page array from the guest to the hypervisor. For
>> example, when
>> a 2MB free page block is reported from the free page list, the info put on
>> the ring is just
>> (base address of the 2MB continuous memory, size=2M).
> So what exactly prevents virtio-balloon from using the above proposed
> callback mechanism and export what is needed to the hypervisor?
I thought about it more. Probably we can use the callback function with
a little change like this:
void walk_free_mem(void *opaque1, void (*visit)(void *opaque2, unsigned
long pfn,
unsigned long nr_pages))
{
...
for_each_populated_zone(zone) {
for_each_migratetype_order(order, type) {
report_unused_page_block(zone, order, type,
&page); // from patch 6
pfn = page_to_pfn(page);
visit(opaque1, pfn, 1 << order);
}
}
}
The above function scans all the free list and directly sends each free
page block to the
hypervisor via the virtio_balloon callback below. No need to implement a
bitmap.
In virtio-balloon, we have the callback:
void *virtio_balloon_report_unused_pages(void *opaque, unsigned long pfn,
unsigned long nr_pages)
{
struct virtio_balloon *vb = (struct virtio_balloon *)opaque;
...put the free page block to the the ring of vb;
}
What do you think?
Best,
Wei
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next prev parent reply other threads:[~2017-07-26 11:41 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-12 12:40 [PATCH v12 0/8] Virtio-balloon Enhancement Wei Wang
2017-07-12 12:40 ` [PATCH v12 1/8] virtio-balloon: deflate via a page list Wei Wang
2017-07-12 12:40 ` [PATCH v12 2/8] virtio-balloon: coding format cleanup Wei Wang
2017-07-12 12:40 ` [PATCH v12 3/8] Introduce xbitmap Wei Wang
2017-07-12 12:40 ` [PATCH v12 4/8] xbitmap: add xb_find_next_bit() and xb_zero() Wei Wang
2017-07-12 12:40 ` [PATCH v12 5/8] virtio-balloon: VIRTIO_BALLOON_F_SG Wei Wang
2017-07-12 13:06 ` Michael S. Tsirkin
2017-07-12 13:29 ` Wei Wang
2017-07-12 13:56 ` Michael S. Tsirkin
2017-07-13 7:42 ` Wei Wang
2017-07-13 20:19 ` Michael S. Tsirkin
2017-07-14 7:12 ` Wei Wang
2017-07-23 1:45 ` Michael S. Tsirkin
2017-07-26 3:48 ` Wei Wang
2017-07-26 17:02 ` Michael S. Tsirkin
2017-07-27 2:50 ` Wei Wang
2017-07-28 23:08 ` Michael S. Tsirkin
2017-07-29 12:47 ` Wei Wang
2017-07-30 4:22 ` Michael S. Tsirkin
2017-07-30 5:59 ` Wang, Wei W
2017-07-30 16:18 ` Michael S. Tsirkin
2017-07-30 16:20 ` Michael S. Tsirkin
2017-07-31 12:36 ` Wei Wang
2017-07-13 0:44 ` Michael S. Tsirkin
2017-07-13 1:16 ` kbuild test robot
2017-07-13 4:21 ` kbuild test robot
2017-07-28 8:25 ` Wei Wang
2017-07-28 23:01 ` Michael S. Tsirkin
2017-07-12 12:40 ` [PATCH v12 6/8] mm: support reporting free page blocks Wei Wang
2017-07-13 0:33 ` Michael S. Tsirkin
2017-07-13 8:25 ` Wei Wang
2017-07-14 12:30 ` Michal Hocko
2017-07-14 12:54 ` Michal Hocko
2017-07-14 15:46 ` Michael S. Tsirkin
2017-07-14 19:17 ` Michael S. Tsirkin
2017-07-17 15:24 ` Michal Hocko
2017-07-18 2:12 ` Wei Wang
2017-07-19 8:13 ` Michal Hocko
2017-07-19 12:01 ` Wei Wang
2017-07-24 9:00 ` Michal Hocko
2017-07-25 9:32 ` Wei Wang
2017-07-25 11:25 ` Michal Hocko
2017-07-25 11:56 ` Wei Wang
2017-07-25 12:41 ` Michal Hocko
2017-07-25 14:47 ` Wang, Wei W
2017-07-25 14:53 ` Michal Hocko
2017-07-26 2:22 ` Wei Wang
2017-07-26 10:24 ` Michal Hocko
2017-07-26 11:44 ` Wei Wang [this message]
2017-07-26 11:55 ` Michal Hocko
2017-07-26 12:47 ` Wang, Wei W
2017-07-12 12:40 ` [PATCH v12 7/8] mm: export symbol of next_zone and first_online_pgdat Wei Wang
2017-07-13 0:16 ` Michael S. Tsirkin
2017-07-13 8:41 ` [virtio-dev] " Wei Wang
2017-07-14 12:31 ` Michal Hocko
2017-07-12 12:40 ` [PATCH v12 8/8] virtio-balloon: VIRTIO_BALLOON_F_CMD_VQ Wei Wang
2017-07-13 0:22 ` Michael S. Tsirkin
2017-07-13 8:46 ` Wei Wang
2017-07-13 17:59 ` Michael S. Tsirkin
2017-07-13 0:14 ` [PATCH v12 0/8] Virtio-balloon Enhancement Michael S. Tsirkin
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