linux-kernel - Re: [PATCH v1 2/2] Drivers: virtio: balloon: Report inflated memory

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Message-ID: <93df4e05-30d7-8176-23a6-948c1bfe4225@virtuozzo.com>
Date:   Mon, 15 Aug 2022 15:52:17 +0300
From:   Alexander Atanasov <alexander.atanasov@...tuozzo.com>
To:     Nadav Amit <namit@...are.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "kernel@...nvz.org" <kernel@...nvz.org>,
        Wei Liu <wei.liu@...nel.org>,
        Linux Virtualization <virtualization@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Pv-drivers <Pv-drivers@...are.com>
Subject: Re: [PATCH v1 2/2] Drivers: virtio: balloon: Report inflated memory

Hi,

On 9.08.22 20:44, Nadav Amit wrote:
> 
> On Aug 9, 2022, at 2:53 AM, Alexander Atanasov <alexander.atanasov@...tuozzo.com> wrote:
> 
>> Update the value in page_alloc on balloon fill/leak.
> 
> Some general comments if this patch goes forward.
> 
> Please cc pv-drivers@...are.com in the future.

Ok.

> 
>>
>> Cc: David Hildenbrand <david@...hat.com>
>> Cc: Wei Liu <wei.liu@...nel.org>
>> Cc: Nadav Amit <namit@...are.com>
>>
>> Signed-off-by: Alexander Atanasov <alexander.atanasov@...tuozzo.com>
>> ---
>> drivers/virtio/virtio_balloon.c | 13 +++++++++++++
>> 1 file changed, 13 insertions(+)
>>
>> Firts user, other balloons i will do if it is accepted to avoid too much emails.
>>
>>
>> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
>> index b9737da6c4dd..e2693ffbd48b 100644
>> --- a/drivers/virtio/virtio_balloon.c
>> +++ b/drivers/virtio/virtio_balloon.c
>> @@ -208,6 +208,16 @@ static void set_page_pfns(struct virtio_balloon *vb,
>> 					  page_to_balloon_pfn(page) + i);
>> }
>>
>> +static void update_meminfo(struct virtio_balloon *vb)
> 
> Putting aside the less-than-optimal function name, I would like to ask that

Right, i will think of a better one.

> any new generic balloon logic would go into balloon_compaction.[hc] as much

If it is going to be a place for generic logic may be it should be 
renamed to balloon_common.[ch] ?

> as possible. I made the effort to reuse this infrastructure (which is now
> used by both VMware and virtio), and would prefer to share as much code as
> possible.
> 
> For instance, I would appreciate if the update upon inflate would go into
> balloon_page_list_enqueue() and balloon_page_enqueue(). VMware's 2MB pages
> logic is not shared, so it would require a change that is specific for
> VMware code.

I looked at the code and i do not see how i can reuse it since
BALLOON_COMPACTION can be disabled and as you say even for VMWare it 
would require updates on other places. Looks like if i do so i would 
have to handle update from each driver for both cases. I think it is 
better to clearly mark the spots when drivers do their internal 
recalculations and report to the core. I see only VMWare is using
balloon_page_list_enqueue , virtio balloon is using only migration and
i don't see how to hook it there - i haven't checked the rest of the 
balloons but i guess it would be similiar . I agree it is a good to have 
a common place for such logic but it might be better of for a separate 
work in the future.

-- 
Regards,
Alexander Atanasov