Re: [Xen-devel] [PATCH] xen-netback: Turn off the carrier if the guest is not able to receive

[David Miller <davem@xxxxxxxxxxxxx>]

From: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
Date: Wed, 30 Jul 2014 20:50:49 +0100

> Currently when the guest is not able to receive more packets, qdisc layer 
> starts
> a timer, and when it goes off, qdisc is started again to deliver a packet 
> again.
> This is a very slow way to drain the queues, consumes unnecessary resources 
> and
> slows down other guests shutdown.
> This patch change the behaviour by turning the carrier off when that timer
> fires, so all the packets are freed up which were stucked waiting for that 
> vif.
> Instead of the rx_queue_purge bool it uses the VIF_STATUS_RX_PURGE_EVENT bit 
> to
> signal the thread that either the timout happened or an RX interrupt arrived, 
> so
> the thread can check what it should do. It also disables NAPI, so the guest
> can't transmit, but leaves the interrupts on, so it can resurrect.
> 
> Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>

When posting a multi-part patch set, number your patches and have a header
"[PATCH 0/N] " posting which describes at a high level what the patch
series is doing, and why.

> +                             for (i = 0; i < num_queues; ++i) {

Please use the more canonical "i++" increment.

Thanks.

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