Re: [Xen-devel] [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@xxxxxxxxxx>]

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

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