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SubjectRe: [Xen-devel] [PATCH net-next v2 2/9] xen-netback: Change TX path from grant copy to mapping
On 17/12/13 21:49, Konrad Rzeszutek Wilk wrote:
> On Thu, Dec 12, 2013 at 11:48:10PM +0000, Zoltan Kiss wrote:
>> @@ -485,6 +520,22 @@ void xenvif_disconnect(struct xenvif *vif)
>>
>> void xenvif_free(struct xenvif *vif)
>> {
>> + int i, unmap_timeout = 0;
>> +
>> + for (i = 0; i < MAX_PENDING_REQS; ++i) {
>> + if (vif->grant_tx_handle[i] != NETBACK_INVALID_HANDLE) {
>> + i = 0;
>> + unmap_timeout++;
>> + msleep(1000);
>
> You don't want to use schedule() and a wakeup here to allow other threads
> to do their work?
Yep, schedule_timeout() would be nicer indeed

>
>> + if (unmap_timeout > 9 &&
>> + net_ratelimit())
>> + netdev_err(vif->dev,
>> + "Page still granted! Index: %x\n", i);
>> + }
>> + }
>> +
>> + free_xenballooned_pages(MAX_PENDING_REQS, vif->mmap_pages);
>
> How about just stashing those pages on a 'I can't free them' list that will
> keep them forever. And if that list gets truly large then switch back to
> grant_copy?
But then what would you answer to the guest? You can't shoot the shared
ring until there is an outstanding slot.
On the other hand, doing a copy would just move the memory leak into the
backend, which could be problematic if a guest figures out how to make a
packet which can get stucked somewhere in the backend.

Zoli


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