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enic: add low latency socket busy_poll support
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This patch adds support for low latency busy_poll.

* Introduce drivers ndo_busy_poll function enic_busy_poll, which is called by
socket waiting for data.

* Introduce locking between napi_poll nad busy_poll

* enic_busy_poll cleans up all the rx pkts possible. While in busy_poll, rq
holds the state ENIC_POLL_STATE_POLL. While in napi_poll, rq holds the state
ENIC_POLL_STATE_NAPI.

* in napi_poll we return if we are in busy_poll. Incase of INTx & msix, we just
service wq and return if busy_poll is going on.

Signed-off-by: Govindarajulu Varadarajan <_govind@gmx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Govindarajulu Varadarajan authored and David S. Miller committed Jun 23, 2014
1 parent 8e09134 commit 14747cd
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Showing 2 changed files with 195 additions and 12 deletions.
85 changes: 73 additions & 12 deletions drivers/net/ethernet/cisco/enic/enic_main.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,9 @@
#ifdef CONFIG_RFS_ACCEL
#include <linux/cpu_rmap.h>
#endif
#ifdef CONFIG_NET_RX_BUSY_POLL
#include <net/busy_poll.h>
#endif

#include "cq_enet_desc.h"
#include "vnic_dev.h"
Expand Down Expand Up @@ -1053,10 +1056,12 @@ static void enic_rq_indicate_buf(struct vnic_rq *rq,
if (vlan_stripped)
__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), vlan_tci);

if (netdev->features & NETIF_F_GRO)
napi_gro_receive(&enic->napi[q_number], skb);
else
skb_mark_napi_id(skb, &enic->napi[rq->index]);
if (enic_poll_busy_polling(rq) ||
!(netdev->features & NETIF_F_GRO))
netif_receive_skb(skb);
else
napi_gro_receive(&enic->napi[q_number], skb);
if (enic->rx_coalesce_setting.use_adaptive_rx_coalesce)
enic_intr_update_pkt_size(&cq->pkt_size_counter,
bytes_written);
Expand Down Expand Up @@ -1093,16 +1098,22 @@ static int enic_poll(struct napi_struct *napi, int budget)
unsigned int work_done, rq_work_done = 0, wq_work_done;
int err;

/* Service RQ (first) and WQ
*/
wq_work_done = vnic_cq_service(&enic->cq[cq_wq], wq_work_to_do,
enic_wq_service, NULL);

if (!enic_poll_lock_napi(&enic->rq[cq_rq])) {
if (wq_work_done > 0)
vnic_intr_return_credits(&enic->intr[intr],
wq_work_done,
0 /* dont unmask intr */,
0 /* dont reset intr timer */);
return rq_work_done;
}

if (budget > 0)
rq_work_done = vnic_cq_service(&enic->cq[cq_rq],
rq_work_to_do, enic_rq_service, NULL);

wq_work_done = vnic_cq_service(&enic->cq[cq_wq],
wq_work_to_do, enic_wq_service, NULL);

/* Accumulate intr event credits for this polling
* cycle. An intr event is the completion of a
* a WQ or RQ packet.
Expand Down Expand Up @@ -1134,6 +1145,7 @@ static int enic_poll(struct napi_struct *napi, int budget)
napi_complete(napi);
vnic_intr_unmask(&enic->intr[intr]);
}
enic_poll_unlock_napi(&enic->rq[cq_rq]);

return rq_work_done;
}
Expand Down Expand Up @@ -1234,6 +1246,34 @@ static void enic_set_rx_cpu_rmap(struct enic *enic)

#endif /* CONFIG_RFS_ACCEL */

#ifdef CONFIG_NET_RX_BUSY_POLL
int enic_busy_poll(struct napi_struct *napi)
{
struct net_device *netdev = napi->dev;
struct enic *enic = netdev_priv(netdev);
unsigned int rq = (napi - &enic->napi[0]);
unsigned int cq = enic_cq_rq(enic, rq);
unsigned int intr = enic_msix_rq_intr(enic, rq);
unsigned int work_to_do = -1; /* clean all pkts possible */
unsigned int work_done;

if (!enic_poll_lock_poll(&enic->rq[rq]))
return LL_FLUSH_BUSY;
work_done = vnic_cq_service(&enic->cq[cq], work_to_do,
enic_rq_service, NULL);

if (work_done > 0)
vnic_intr_return_credits(&enic->intr[intr],
work_done, 0, 0);
vnic_rq_fill(&enic->rq[rq], enic_rq_alloc_buf);
if (enic->rx_coalesce_setting.use_adaptive_rx_coalesce)
enic_calc_int_moderation(enic, &enic->rq[rq]);
enic_poll_unlock_poll(&enic->rq[rq]);

return work_done;
}
#endif /* CONFIG_NET_RX_BUSY_POLL */

static int enic_poll_msix(struct napi_struct *napi, int budget)
{
struct net_device *netdev = napi->dev;
Expand All @@ -1245,6 +1285,8 @@ static int enic_poll_msix(struct napi_struct *napi, int budget)
unsigned int work_done = 0;
int err;

if (!enic_poll_lock_napi(&enic->rq[rq]))
return work_done;
/* Service RQ
*/

Expand Down Expand Up @@ -1290,6 +1332,7 @@ static int enic_poll_msix(struct napi_struct *napi, int budget)
enic_set_int_moderation(enic, &enic->rq[rq]);
vnic_intr_unmask(&enic->intr[intr]);
}
enic_poll_unlock_napi(&enic->rq[rq]);

return work_done;
}
Expand Down Expand Up @@ -1538,8 +1581,10 @@ static int enic_open(struct net_device *netdev)

netif_tx_wake_all_queues(netdev);

for (i = 0; i < enic->rq_count; i++)
for (i = 0; i < enic->rq_count; i++) {
enic_busy_poll_init_lock(&enic->rq[i]);
napi_enable(&enic->napi[i]);
}

enic_dev_enable(enic);

Expand Down Expand Up @@ -1578,8 +1623,13 @@ static int enic_stop(struct net_device *netdev)

enic_dev_disable(enic);

for (i = 0; i < enic->rq_count; i++)
local_bh_disable();
for (i = 0; i < enic->rq_count; i++) {
napi_disable(&enic->napi[i]);
while (!enic_poll_lock_napi(&enic->rq[i]))
mdelay(1);
}
local_bh_enable();

netif_carrier_off(netdev);
netif_tx_disable(netdev);
Expand Down Expand Up @@ -2070,6 +2120,9 @@ static const struct net_device_ops enic_netdev_dynamic_ops = {
#ifdef CONFIG_RFS_ACCEL
.ndo_rx_flow_steer = enic_rx_flow_steer,
#endif
#ifdef CONFIG_NET_RX_BUSY_POLL
.ndo_busy_poll = enic_busy_poll,
#endif
};

static const struct net_device_ops enic_netdev_ops = {
Expand All @@ -2093,14 +2146,19 @@ static const struct net_device_ops enic_netdev_ops = {
#ifdef CONFIG_RFS_ACCEL
.ndo_rx_flow_steer = enic_rx_flow_steer,
#endif
#ifdef CONFIG_NET_RX_BUSY_POLL
.ndo_busy_poll = enic_busy_poll,
#endif
};

static void enic_dev_deinit(struct enic *enic)
{
unsigned int i;

for (i = 0; i < enic->rq_count; i++)
for (i = 0; i < enic->rq_count; i++) {
napi_hash_del(&enic->napi[i]);
netif_napi_del(&enic->napi[i]);
}

enic_free_vnic_resources(enic);
enic_clear_intr_mode(enic);
Expand Down Expand Up @@ -2166,11 +2224,14 @@ static int enic_dev_init(struct enic *enic)
switch (vnic_dev_get_intr_mode(enic->vdev)) {
default:
netif_napi_add(netdev, &enic->napi[0], enic_poll, 64);
napi_hash_add(&enic->napi[0]);
break;
case VNIC_DEV_INTR_MODE_MSIX:
for (i = 0; i < enic->rq_count; i++)
for (i = 0; i < enic->rq_count; i++) {
netif_napi_add(netdev, &enic->napi[i],
enic_poll_msix, 64);
napi_hash_add(&enic->napi[i]);
}
break;
}

Expand Down
122 changes: 122 additions & 0 deletions drivers/net/ethernet/cisco/enic/vnic_rq.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,21 @@ struct vnic_rq {
struct vnic_rq_buf *to_clean;
void *os_buf_head;
unsigned int pkts_outstanding;
#ifdef CONFIG_NET_RX_BUSY_POLL
#define ENIC_POLL_STATE_IDLE 0
#define ENIC_POLL_STATE_NAPI (1 << 0) /* NAPI owns this poll */
#define ENIC_POLL_STATE_POLL (1 << 1) /* poll owns this poll */
#define ENIC_POLL_STATE_NAPI_YIELD (1 << 2) /* NAPI yielded this poll */
#define ENIC_POLL_STATE_POLL_YIELD (1 << 3) /* poll yielded this poll */
#define ENIC_POLL_YIELD (ENIC_POLL_STATE_NAPI_YIELD | \
ENIC_POLL_STATE_POLL_YIELD)
#define ENIC_POLL_LOCKED (ENIC_POLL_STATE_NAPI | \
ENIC_POLL_STATE_POLL)
#define ENIC_POLL_USER_PEND (ENIC_POLL_STATE_POLL | \
ENIC_POLL_STATE_POLL_YIELD)
unsigned int bpoll_state;
spinlock_t bpoll_lock;
#endif /* CONFIG_NET_RX_BUSY_POLL */
};

static inline unsigned int vnic_rq_desc_avail(struct vnic_rq *rq)
Expand Down Expand Up @@ -197,6 +212,113 @@ static inline int vnic_rq_fill(struct vnic_rq *rq,
return 0;
}

#ifdef CONFIG_NET_RX_BUSY_POLL
static inline void enic_busy_poll_init_lock(struct vnic_rq *rq)
{
spin_lock_init(&rq->bpoll_lock);
rq->bpoll_state = ENIC_POLL_STATE_IDLE;
}

static inline bool enic_poll_lock_napi(struct vnic_rq *rq)
{
bool rc = true;

spin_lock(&rq->bpoll_lock);
if (rq->bpoll_state & ENIC_POLL_LOCKED) {
WARN_ON(rq->bpoll_state & ENIC_POLL_STATE_NAPI);
rq->bpoll_state |= ENIC_POLL_STATE_NAPI_YIELD;
rc = false;
} else {
rq->bpoll_state = ENIC_POLL_STATE_NAPI;
}
spin_unlock(&rq->bpoll_lock);

return rc;
}

static inline bool enic_poll_unlock_napi(struct vnic_rq *rq)
{
bool rc = false;

spin_lock(&rq->bpoll_lock);
WARN_ON(rq->bpoll_state &
(ENIC_POLL_STATE_POLL | ENIC_POLL_STATE_NAPI_YIELD));
if (rq->bpoll_state & ENIC_POLL_STATE_POLL_YIELD)
rc = true;
rq->bpoll_state = ENIC_POLL_STATE_IDLE;
spin_unlock(&rq->bpoll_lock);

return rc;
}

static inline bool enic_poll_lock_poll(struct vnic_rq *rq)
{
bool rc = true;

spin_lock_bh(&rq->bpoll_lock);
if (rq->bpoll_state & ENIC_POLL_LOCKED) {
rq->bpoll_state |= ENIC_POLL_STATE_POLL_YIELD;
rc = false;
} else {
rq->bpoll_state |= ENIC_POLL_STATE_POLL;
}
spin_unlock_bh(&rq->bpoll_lock);

return rc;
}

static inline bool enic_poll_unlock_poll(struct vnic_rq *rq)
{
bool rc = false;

spin_lock_bh(&rq->bpoll_lock);
WARN_ON(rq->bpoll_state & ENIC_POLL_STATE_NAPI);
if (rq->bpoll_state & ENIC_POLL_STATE_POLL_YIELD)
rc = true;
rq->bpoll_state = ENIC_POLL_STATE_IDLE;
spin_unlock_bh(&rq->bpoll_lock);

return rc;
}

static inline bool enic_poll_busy_polling(struct vnic_rq *rq)
{
WARN_ON(!(rq->bpoll_state & ENIC_POLL_LOCKED));
return rq->bpoll_state & ENIC_POLL_USER_PEND;
}

#else

static inline void enic_busy_poll_init_lock(struct vnic_rq *rq)
{
}

static inline bool enic_poll_lock_napi(struct vnic_rq *rq)
{
return true;
}

static inline bool enic_poll_unlock_napi(struct vnic_rq *rq)
{
return false;
}

static inline bool enic_poll_lock_poll(struct vnic_rq *rq)
{
return false;
}

static inline bool enic_poll_unlock_poll(struct vnic_rq *rq)
{
return false;
}

static inline bool enic_poll_ll_polling(struct vnic_rq *rq)
{
return false;
}
#endif /* CONFIG_NET_RX_BUSY_POLL */

void vnic_rq_free(struct vnic_rq *rq);
int vnic_rq_alloc(struct vnic_dev *vdev, struct vnic_rq *rq, unsigned int index,
unsigned int desc_count, unsigned int desc_size);
Expand Down

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