Re: [Xen-devel] [PATCH net-next v5 2/9] xen-netback: Change TX path from grant copy to mapping

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 19/02/14 09:54, Ian Campbell wrote:
> On Tue, 2014-02-18 at 18:46 +0000, David Vrabel wrote:
>> On 18/02/14 17:40, Ian Campbell wrote:
>>> On Mon, 2014-01-20 at 21:24 +0000, Zoltan Kiss wrote:
>>>>
>>>> @@ -344,8 +346,26 @@ struct xenvif *xenvif_alloc(struct device *parent, 
>>>> domid_t domid,
>>>>    vif->pending_prod = MAX_PENDING_REQS;
>>>>    for (i = 0; i < MAX_PENDING_REQS; i++)
>>>>            vif->pending_ring[i] = i;
>>>> -  for (i = 0; i < MAX_PENDING_REQS; i++)
>>>> -          vif->mmap_pages[i] = NULL;
>>>> +  spin_lock_init(&vif->dealloc_lock);
>>>> +  spin_lock_init(&vif->response_lock);
>>>> +  /* If ballooning is disabled, this will consume real memory, so you
>>>> +   * better enable it.
>>>
>>> Almost no one who would be affected by this is going to read this
>>> comment. And it doesn't just require enabling ballooning, but actually
>>> booting with some maxmem "slack" to leave space.
>>>
>>> Classic-xen kernels used to add 8M of slop to the physical address space
>>> to leave a suitable pool for exactly this sort of thing. I never liked
>>> that but perhaps it should be reconsidered (or at least raised as a
>>> possibility with the core-Xen Linux guys).
>>
>> I plan to fix the balloon memory hotplug stuff to do the right thing
> 
> Which is for alloc_xenballoon_pages to hotplug a new empty region,
> rather than inflating the balloon if it doesn't have enough pages to
> satisfy the allocation?

Yes.

David

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