From: David Hildenbrand <david@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alexander Duyck <alexander.duyck@gmail.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org,
akpm@linux-foundation.org, mgorman@techsingularity.net,
vbabka@suse.cz, yang.zhang.wz@gmail.com, nitesh@redhat.com,
konrad.wilk@oracle.com, pagupta@redhat.com, riel@surriel.com,
lcapitulino@redhat.com, dave.hansen@intel.com,
wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com,
dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com,
osalvador@suse.de
Subject: Re: [PATCH v16.1 6/9] virtio-balloon: Add support for providing free page reports to host
Date: Tue, 11 Feb 2020 15:31:18 +0100 [thread overview]
Message-ID: <d6b481fb-6c72-455d-f8e4-600a8677c7a8@redhat.com> (raw)
In-Reply-To: <20200211090052-mutt-send-email-mst@kernel.org>
On 11.02.20 15:07, Michael S. Tsirkin wrote:
> On Tue, Feb 11, 2020 at 01:19:31PM +0100, David Hildenbrand wrote:
>>>>
>>>> Did you see the discussion regarding unifying handling of
>>>> inflate/deflate/free_page_hinting_free_page_reporting, requested by
>>>> Michael? I think free page reporting is special and shall be left alone.
>>>
>>> Not sure what do you mean by "left alone here". Could you clarify?
>>
>> Don't try to unify handling like I proposed below, because it's
>> semantics are special.
>>
>>>
>>>> VIRTIO_BALLOON_F_REPORTING is nothing but a more advanced inflate, right
>>>> (sg, inflate based on size - not "virtio pages")?
>>>
>>>
>>> Not exactly - it's also initiated by guest as opposed to host, and
>>> not guided by the ballon size request set by the host.
>>
>> True, but AFAIKS you could use existing INFLATE/DEFLATE in a similar
>> way. There is no way for the hypervisor to nack a request. The balloon
>> size is not glued to inflate/deflate requests. The guests manually
>> updates it.
>
> Hmm how isn't it? num_pages is the only way to inflate/deflate.
Usually, guests are nice and respond to num_pages changes in an
appropriate way, except:
- Triggering deflate: Unload the driver. Suspend/hibernate. OOM.
(+ Reboot, although that's special)
- Triggering inflate + deflate: Simple balloon compaction / page
migration.
But that's not what I meant.
"actual" is updated by the guest, not by the host. So the "actual
balloon size" is set by the guest. It's not glued to inflation/deflation
requests. "num_pages" is the host request.
AFAIKs, the guest could inflate/deflate (esp. temporarily) and
communicate via "actual" the actual balloon size as he sees it.
> Spec also says:
> The device is driven either by the receipt of a configuration change notification, or by changing guest memory
> needs, such as performing memory compaction or responding to out of memory conditions.
>
> so ignoring compaction/oom (later is under-specified, not a good example
> to follow) yes inflate/deflate are tied to host specified configuration
Yes, "num_pages" is the host request. But I'd say the statement (esp.
"the device is driven by") in the spec is rather weak. It does not
explicitly state when inflation/deflation is allowed IMHO.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-02-11 14:31 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-22 17:43 [PATCH v16.1 0/9] mm / virtio: Provide support for free page reporting Alexander Duyck
2020-01-22 17:43 ` [PATCH v16.1 1/9] mm: Adjust shuffle code to allow for future coalescing Alexander Duyck
2020-01-22 17:43 ` [PATCH v16.1 2/9] mm: Use zone and order instead of free area in free_list manipulators Alexander Duyck
2020-01-22 17:43 ` [PATCH v16.1 3/9] mm: Add function __putback_isolated_page Alexander Duyck
2020-01-22 17:43 ` [PATCH v16.1 4/9] mm: Introduce Reported pages Alexander Duyck
2020-01-22 17:43 ` [PATCH v16.1 5/9] virtio-balloon: Pull page poisoning config out of free page hinting Alexander Duyck
2020-01-22 17:43 ` [PATCH v16.1 6/9] virtio-balloon: Add support for providing free page reports to host Alexander Duyck
2020-02-11 11:03 ` David Hildenbrand
2020-02-11 11:47 ` Michael S. Tsirkin
2020-02-11 12:19 ` David Hildenbrand
2020-02-11 14:07 ` Michael S. Tsirkin
2020-02-11 14:31 ` David Hildenbrand [this message]
2020-02-11 14:48 ` Michael S. Tsirkin
2020-02-11 15:13 ` David Hildenbrand
2020-02-11 16:33 ` Alexander Duyck
2020-02-11 17:04 ` David Hildenbrand
2020-01-22 17:43 ` [PATCH v16.1 7/9] mm/page_reporting: Rotate reported pages to the tail of the list Alexander Duyck
2020-01-22 17:43 ` [PATCH v16.1 8/9] mm/page_reporting: Add budget limit on how many pages can be reported per pass Alexander Duyck
2020-01-22 17:44 ` [PATCH v16.1 9/9] mm/page_reporting: Add free page reporting documentation Alexander Duyck
2020-01-23 10:20 ` [PATCH v16.1 0/9] mm / virtio: Provide support for free page reporting Alexander Graf
2020-01-23 14:05 ` David Hildenbrand
2020-01-23 14:52 ` Alexander Graf
2020-01-24 13:25 ` David Hildenbrand
2020-01-24 16:20 ` David Hildenbrand
2020-01-23 16:26 ` Alexander Duyck
2020-01-23 16:54 ` Alexander Graf
2020-01-23 18:33 ` Alexander Duyck
2020-01-23 18:47 ` Graf (AWS), Alexander
2020-01-23 22:05 ` Alexander Duyck
2020-01-23 17:20 ` Dave Hansen
2020-01-23 19:23 ` Konrad Rzeszutek Wilk
2020-01-23 19:17 ` Johannes Weiner
2020-01-23 22:29 ` Alexander Duyck
2020-01-23 23:24 ` Dave Hansen
[not found] ` <20200124132352.12824-1-hdanton@sina.com>
2020-01-24 16:40 ` Alexander Graf
2020-02-03 22:05 ` Alexander Duyck
2020-02-10 19:18 ` Should I repost? (was: Re: [PATCH v16.1 0/9] mm / virtio: Provide support for free page reporting) Alexander Duyck
2020-02-11 10:40 ` Mel Gorman
2020-02-11 22:57 ` Alexander Duyck
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