Sasha Levin <[email protected]> writes:
> Due to MQ support we may allocate a whole bunch of rx queues but
> never use them. With this patch we'll safe the space used by
> the receive buffers until they are actually in use:

Idea is good, implementation needs a tiny tweak:

> @@ -912,8 +913,13 @@ static int virtnet_set_queues(struct virtnet_info *vi, 
> u16 queue_pairs)
>               dev_warn(&dev->dev, "Fail to set num of queue pairs to %d\n",
>                        queue_pairs);
>               return -EINVAL;
> -     } else
> +     } else {
> +             if (queue_pairs > vi->curr_queue_pairs)
> +                     for (i = 0; i < queue_pairs; i++)
> +                             if (!try_fill_recv(&vi->rq[i], GFP_KERNEL))
> +                                     schedule_delayed_work(&vi->refill, 0);
>               vi->curr_queue_pairs = queue_pairs;
> +     }
>  
>       return 0;
>  }

You don't want to refill existing queues, so you don't need the "if".

        for (i = vi->curr_queue_pairs; i < queue_pairs; i++) {
                if (!try_fill_recv(&vi->rq[i], GFP_KERNEL))
                        schedule_delayed_work(&vi->refill, 0);

We don't free up buffers when we're reducing queues, but I consider that
a corner case.

Thanks,
Rusty.
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