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net: RPS: Enable hardware acceleration of RFS

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Allow drivers for multiqueue hardware with flow filter tables to
accelerate RFS.  The driver must:

1. Set net_device::rx_cpu_rmap to a cpu_rmap of the RX completion
IRQs (in queue order).  This will provide a mapping from CPUs to the
queues for which completions are handled nearest to them.

2. Implement net_device_ops::ndo_rx_flow_steer.  This operation adds
or replaces a filter steering the given flow to the given RX queue, if
possible.

3. Periodically remove filters for which rps_may_expire_flow() returns
true.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ben Hutchings
2011-01-19 11:03:53 +00:00
committed by David S. Miller
parent c39649c331
commit c445477d74
3 changed files with 127 additions and 9 deletions
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97
net/core/dev.c
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@ -132,6 +132,7 @@
#include <trace/events/skb.h>
#include <linux/pci.h>
#include <linux/inetdevice.h>
#include <linux/cpu_rmap.h>
#include "net-sysfs.h"
@ -2588,6 +2589,53 @@ EXPORT_SYMBOL(__skb_get_rxhash);
struct rps_sock_flow_table __rcu *rps_sock_flow_table __read_mostly;
EXPORT_SYMBOL(rps_sock_flow_table);
static struct rps_dev_flow *
set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
struct rps_dev_flow *rflow, u16 next_cpu)
{
u16 tcpu;
tcpu = rflow->cpu = next_cpu;
if (tcpu != RPS_NO_CPU) {
#ifdef CONFIG_RFS_ACCEL
struct netdev_rx_queue *rxqueue;
struct rps_dev_flow_table *flow_table;
struct rps_dev_flow *old_rflow;
u32 flow_id;
u16 rxq_index;
int rc;
/* Should we steer this flow to a different hardware queue? */
if (!skb_rx_queue_recorded(skb) || !dev->rx_cpu_rmap)
goto out;
rxq_index = cpu_rmap_lookup_index(dev->rx_cpu_rmap, next_cpu);
if (rxq_index == skb_get_rx_queue(skb))
goto out;
rxqueue = dev->_rx + rxq_index;
flow_table = rcu_dereference(rxqueue->rps_flow_table);
if (!flow_table)
goto out;
flow_id = skb->rxhash & flow_table->mask;
rc = dev->netdev_ops->ndo_rx_flow_steer(dev, skb,
rxq_index, flow_id);
if (rc < 0)
goto out;
old_rflow = rflow;
rflow = &flow_table->flows[flow_id];
rflow->cpu = next_cpu;
rflow->filter = rc;
if (old_rflow->filter == rflow->filter)
old_rflow->filter = RPS_NO_FILTER;
out:
#endif
rflow->last_qtail =
per_cpu(softnet_data, tcpu).input_queue_head;
}
return rflow;
}
/*
* get_rps_cpu is called from netif_receive_skb and returns the target
* CPU from the RPS map of the receiving queue for a given skb.
@ -2658,12 +2706,9 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
if (unlikely(tcpu != next_cpu) &&
(tcpu == RPS_NO_CPU || !cpu_online(tcpu) ||
((int)(per_cpu(softnet_data, tcpu).input_queue_head -
rflow->last_qtail)) >= 0)) {
tcpu = rflow->cpu = next_cpu;
if (tcpu != RPS_NO_CPU)
rflow->last_qtail = per_cpu(softnet_data,
tcpu).input_queue_head;
}
rflow->last_qtail)) >= 0))
rflow = set_rps_cpu(dev, skb, rflow, next_cpu);
if (tcpu != RPS_NO_CPU && cpu_online(tcpu)) {
*rflowp = rflow;
cpu = tcpu;
@ -2684,6 +2729,46 @@ done:
return cpu;
}
#ifdef CONFIG_RFS_ACCEL
/**
* rps_may_expire_flow - check whether an RFS hardware filter may be removed
* @dev: Device on which the filter was set
* @rxq_index: RX queue index
* @flow_id: Flow ID passed to ndo_rx_flow_steer()
* @filter_id: Filter ID returned by ndo_rx_flow_steer()
*
* Drivers that implement ndo_rx_flow_steer() should periodically call
* this function for each installed filter and remove the filters for
* which it returns %true.
*/
bool rps_may_expire_flow(struct net_device *dev, u16 rxq_index,
u32 flow_id, u16 filter_id)
{
struct netdev_rx_queue *rxqueue = dev->_rx + rxq_index;
struct rps_dev_flow_table *flow_table;
struct rps_dev_flow *rflow;
bool expire = true;
int cpu;
rcu_read_lock();
flow_table = rcu_dereference(rxqueue->rps_flow_table);
if (flow_table && flow_id <= flow_table->mask) {
rflow = &flow_table->flows[flow_id];
cpu = ACCESS_ONCE(rflow->cpu);
if (rflow->filter == filter_id && cpu != RPS_NO_CPU &&
((int)(per_cpu(softnet_data, cpu).input_queue_head -
rflow->last_qtail) <
(int)(10 * flow_table->mask)))
expire = false;
}
rcu_read_unlock();
return expire;
}
EXPORT_SYMBOL(rps_may_expire_flow);
#endif /* CONFIG_RFS_ACCEL */
/* Called from hardirq (IPI) context */
static void rps_trigger_softirq(void *data)
{