From: Matthias Tafelmeier <[email protected]>
Date: Wed, 28 Dec 2016 10:42:14 +0100
> @@ -3428,6 +3428,8 @@ EXPORT_SYMBOL(netdev_max_backlog);
> int netdev_tstamp_prequeue __read_mostly = 1;
> int netdev_budget __read_mostly = 300;
> int weight_p __read_mostly = 64; /* old backlog weight */
> +int dev_weight_rx_bias __read_mostly = 1; /* bias for backlog
> weight */
> +int dev_weight_tx_bias __read_mostly = 1; /* bias for
> output_queue quota */
>
> /* Called with irq disabled */
> static inline void ____napi_schedule(struct softnet_data *sd,
> @@ -4833,7 +4835,7 @@ static int process_backlog(struct napi_struct *napi,
> int quota)
> net_rps_action_and_irq_enable(sd);
> }
>
> - napi->weight = weight_p;
> + napi->weight = weight_p * dev_weight_rx_bias;
> while (again) {
> struct sk_buff *skb;
>
...
> @@ -247,7 +247,7 @@ static inline int qdisc_restart(struct Qdisc *q, int
> *packets)
>
> void __qdisc_run(struct Qdisc *q)
> {
> - int quota = weight_p;
> + int quota = weight_p * dev_weight_tx_bias;
Ok, this is a lot better than what you proposed initially.
However, being that this is the fast path for all packet processing,
introducing a multiply here doesn't sit well.
I think there are two possible ways to address this:
1) Make the bias instead be a "shift".
2) Precompute the dev_tx_weight and dev_rx_weight into two variables
in net/core/dev.c Install a special proc_dointvec handler for
"dev_weight" that, upon proc_dointvec() success, updates both
dev_tx_weight and dev_rx_weight based upon the bias settings.
