Re: [PATCH] fix netfront alloc_page error handling bug, need to raise up rx_refill timer if rx request buffer not big enough for backend

[annie li <annie.li@oracle.com>]

On 2013-11-14 19:38, David Vrabel wrote:
> On 14/11/13 02:39, annie li wrote:
>> With this assumption, is it easier to fix this issue by moving mod_timer
>> directly
>>              mod_timer(&np->rx_refill_timer,
>>                    jiffies + (HZ/10));
>> above
>>              if (i != 0)
>>                  goto refill;
>>
>> in xennet_alloc_rx_buffers?
> Yes, always setting the timer if we didn't reach the target is a better
> fix I think.
>
> However, we probably want to reduce the fill target if we are under
> memory pressure.
>
> Something like:
>
> no_skb:
>                 /* Memory pressure, reduce fill target. */
> 	       if (--np->rx_target < np->rx_target_min)
>                     np->rx_target = np->rx_target_min;
>                 mod_timer(...);
>                 goto refill;
>
> perhaps?

Sounds reasonable.
When less memory is availble, then reduce rx_target to decrease 
requirement of memory. And rx_target can be adjusted back after memory 
is enough in following code,

     if (((req_prod - np->rx.sring->rsp_prod) < (np->rx_target / 4)) &&
         ((np->rx_target *= 2) > np->rx_max_target))
         np->rx_target = np->rx_max_target;

Thanks
Annie
>
> David