On Mon, Jun 25, 2018 at 11:04 AM, Amritha Nambiar
<amritha.namb...@intel.com> wrote:
> Use static_key for XPS maps to reduce the cost of extra map checks,
> similar to how it is used for RPS and RFS. This includes static_key
> 'xps_needed' for XPS and another for 'xps_rxqs_needed' for XPS using
> Rx queues map.
>
Acked-by: Tom Herbert <t...@quantonium.net>
> Signed-off-by: Amritha Nambiar <amritha.namb...@intel.com>
> ---
> net/core/dev.c | 26 ++++++++++++++++++++------
> 1 file changed, 20 insertions(+), 6 deletions(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 2552556..df2a78d 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2081,6 +2081,10 @@ int netdev_txq_to_tc(struct net_device *dev, unsigned
> int txq)
> EXPORT_SYMBOL(netdev_txq_to_tc);
>
> #ifdef CONFIG_XPS
> +struct static_key xps_needed __read_mostly;
> +EXPORT_SYMBOL(xps_needed);
> +struct static_key xps_rxqs_needed __read_mostly;
> +EXPORT_SYMBOL(xps_rxqs_needed);
> static DEFINE_MUTEX(xps_map_mutex);
> #define xmap_dereference(P) \
> rcu_dereference_protected((P), lockdep_is_held(&xps_map_mutex))
> @@ -2170,12 +2174,14 @@ static void netif_reset_xps_queues(struct net_device
> *dev, u16 offset,
>
> mutex_lock(&xps_map_mutex);
>
> - dev_maps = xmap_dereference(dev->xps_rxqs_map);
> - if (dev_maps) {
> - nr_ids = dev->num_rx_queues;
> - clean_xps_maps(dev, possible_mask, dev_maps, nr_ids, offset,
> - count, true);
> -
> + if (static_key_false(&xps_rxqs_needed)) {
> + dev_maps = xmap_dereference(dev->xps_rxqs_map);
> + if (dev_maps) {
> + nr_ids = dev->num_rx_queues;
> + clean_xps_maps(dev, possible_mask, dev_maps, nr_ids,
> + offset, count, true);
> + }
> + static_key_slow_dec(&xps_rxqs_needed);
> }
>
> dev_maps = xmap_dereference(dev->xps_cpus_map);
> @@ -2189,6 +2195,7 @@ static void netif_reset_xps_queues(struct net_device
> *dev, u16 offset,
> false);
>
> out_no_maps:
> + static_key_slow_dec(&xps_needed);
> mutex_unlock(&xps_map_mutex);
> }
>
> @@ -2297,6 +2304,10 @@ int __netif_set_xps_queue(struct net_device *dev,
> const unsigned long *mask,
> if (!new_dev_maps)
> goto out_no_new_maps;
>
> + static_key_slow_inc(&xps_needed);
> + if (is_rxqs_map)
> + static_key_slow_inc(&xps_rxqs_needed);
> +
> for (j = -1; j = attrmask_next(j, possible_mask, nr_ids),
> j < nr_ids;) {
> /* copy maps belonging to foreign traffic classes */
> @@ -3450,6 +3461,9 @@ static inline int get_xps_queue(struct net_device *dev,
> struct sk_buff *skb)
> struct xps_map *map;
> int queue_index = -1;
>
> + if (!static_key_false(&xps_needed))
> + return -1;
> +
> rcu_read_lock();
> dev_maps = rcu_dereference(dev->xps_cpus_map);
> if (dev_maps) {
>
