Commit 3a336cb1 authored by Hariprasad Shenai's avatar Hariprasad Shenai Committed by David S. Miller
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cxgb4: Add low latency socket busy_poll support



cxgb_busy_poll, corresponding to ndo_busy_poll, gets called by the socket
waiting for data.

With busy_poll enabled, improvement is seen in latency numbers as observed by
collecting netperf TCP_RR numbers.
Below are latency number, with and without busy-poll, in a switched environment
for a particular msg size:
netperf command: netperf -4 -H <ip> -l 30 -t TCP_RR -- -r1,1
Latency without busy-poll: ~16.25 us
Latency with busy-poll   : ~08.79 us

Based on original work by Kumar Sanghvi <kumaras@chelsio.com>
Signed-off-by: default avatarHariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3fcf9011
......@@ -476,6 +476,22 @@ struct sge_rspq { /* state for an SGE response queue */
struct adapter *adap;
struct net_device *netdev; /* associated net device */
rspq_handler_t handler;
#ifdef CONFIG_NET_RX_BUSY_POLL
#define CXGB_POLL_STATE_IDLE 0
#define CXGB_POLL_STATE_NAPI BIT(0) /* NAPI owns this poll */
#define CXGB_POLL_STATE_POLL BIT(1) /* poll owns this poll */
#define CXGB_POLL_STATE_NAPI_YIELD BIT(2) /* NAPI yielded this poll */
#define CXGB_POLL_STATE_POLL_YIELD BIT(3) /* poll yielded this poll */
#define CXGB_POLL_YIELD (CXGB_POLL_STATE_NAPI_YIELD | \
CXGB_POLL_STATE_POLL_YIELD)
#define CXGB_POLL_LOCKED (CXGB_POLL_STATE_NAPI | \
CXGB_POLL_STATE_POLL)
#define CXGB_POLL_USER_PEND (CXGB_POLL_STATE_POLL | \
CXGB_POLL_STATE_POLL_YIELD)
unsigned int bpoll_state;
spinlock_t bpoll_lock; /* lock for busy poll */
#endif /* CONFIG_NET_RX_BUSY_POLL */
};
struct sge_eth_stats { /* Ethernet queue statistics */
......@@ -880,6 +896,102 @@ static inline struct adapter *netdev2adap(const struct net_device *dev)
return netdev2pinfo(dev)->adapter;
}
#ifdef CONFIG_NET_RX_BUSY_POLL
static inline void cxgb_busy_poll_init_lock(struct sge_rspq *q)
{
spin_lock_init(&q->bpoll_lock);
q->bpoll_state = CXGB_POLL_STATE_IDLE;
}
static inline bool cxgb_poll_lock_napi(struct sge_rspq *q)
{
bool rc = true;
spin_lock(&q->bpoll_lock);
if (q->bpoll_state & CXGB_POLL_LOCKED) {
q->bpoll_state |= CXGB_POLL_STATE_NAPI_YIELD;
rc = false;
} else {
q->bpoll_state = CXGB_POLL_STATE_NAPI;
}
spin_unlock(&q->bpoll_lock);
return rc;
}
static inline bool cxgb_poll_unlock_napi(struct sge_rspq *q)
{
bool rc = false;
spin_lock(&q->bpoll_lock);
if (q->bpoll_state & CXGB_POLL_STATE_POLL_YIELD)
rc = true;
q->bpoll_state = CXGB_POLL_STATE_IDLE;
spin_unlock(&q->bpoll_lock);
return rc;
}
static inline bool cxgb_poll_lock_poll(struct sge_rspq *q)
{
bool rc = true;
spin_lock_bh(&q->bpoll_lock);
if (q->bpoll_state & CXGB_POLL_LOCKED) {
q->bpoll_state |= CXGB_POLL_STATE_POLL_YIELD;
rc = false;
} else {
q->bpoll_state |= CXGB_POLL_STATE_POLL;
}
spin_unlock_bh(&q->bpoll_lock);
return rc;
}
static inline bool cxgb_poll_unlock_poll(struct sge_rspq *q)
{
bool rc = false;
spin_lock_bh(&q->bpoll_lock);
if (q->bpoll_state & CXGB_POLL_STATE_POLL_YIELD)
rc = true;
q->bpoll_state = CXGB_POLL_STATE_IDLE;
spin_unlock_bh(&q->bpoll_lock);
return rc;
}
static inline bool cxgb_poll_busy_polling(struct sge_rspq *q)
{
return q->bpoll_state & CXGB_POLL_USER_PEND;
}
#else
static inline void cxgb_busy_poll_init_lock(struct sge_rspq *q)
{
}
static inline bool cxgb_poll_lock_napi(struct sge_rspq *q)
{
return true;
}
static inline bool cxgb_poll_unlock_napi(struct sge_rspq *q)
{
return false;
}
static inline bool cxgb_poll_lock_poll(struct sge_rspq *q)
{
return false;
}
static inline bool cxgb_poll_unlock_poll(struct sge_rspq *q)
{
return false;
}
static inline bool cxgb_poll_busy_polling(struct sge_rspq *q)
{
return false;
}
#endif /* CONFIG_NET_RX_BUSY_POLL */
void t4_os_portmod_changed(const struct adapter *adap, int port_id);
void t4_os_link_changed(struct adapter *adap, int port_id, int link_stat);
......@@ -908,6 +1020,7 @@ irqreturn_t t4_sge_intr_msix(int irq, void *cookie);
int t4_sge_init(struct adapter *adap);
void t4_sge_start(struct adapter *adap);
void t4_sge_stop(struct adapter *adap);
int cxgb_busy_poll(struct napi_struct *napi);
extern int dbfifo_int_thresh;
#define for_each_port(adapter, iter) \
......
......@@ -923,8 +923,14 @@ static void quiesce_rx(struct adapter *adap)
for (i = 0; i < ARRAY_SIZE(adap->sge.ingr_map); i++) {
struct sge_rspq *q = adap->sge.ingr_map[i];
if (q && q->handler)
if (q && q->handler) {
napi_disable(&q->napi);
local_bh_disable();
while (!cxgb_poll_lock_napi(q))
mdelay(1);
local_bh_enable();
}
}
}
......@@ -940,8 +946,10 @@ static void enable_rx(struct adapter *adap)
if (!q)
continue;
if (q->handler)
if (q->handler) {
cxgb_busy_poll_init_lock(q);
napi_enable(&q->napi);
}
/* 0-increment GTS to start the timer and enable interrupts */
t4_write_reg(adap, MYPF_REG(SGE_PF_GTS_A),
SEINTARM_V(q->intr_params) |
......@@ -4563,6 +4571,10 @@ static const struct net_device_ops cxgb4_netdev_ops = {
#ifdef CONFIG_NET_POLL_CONTROLLER
.ndo_poll_controller = cxgb_netpoll,
#endif
#ifdef CONFIG_NET_RX_BUSY_POLL
.ndo_busy_poll = cxgb_busy_poll,
#endif
};
void t4_fatal_err(struct adapter *adap)
......
......@@ -43,6 +43,9 @@
#include <linux/export.h>
#include <net/ipv6.h>
#include <net/tcp.h>
#ifdef CONFIG_NET_RX_BUSY_POLL
#include <net/busy_poll.h>
#endif /* CONFIG_NET_RX_BUSY_POLL */
#include "cxgb4.h"
#include "t4_regs.h"
#include "t4_values.h"
......@@ -1720,6 +1723,7 @@ static void do_gro(struct sge_eth_rxq *rxq, const struct pkt_gl *gl,
skb->truesize += skb->data_len;
skb->ip_summed = CHECKSUM_UNNECESSARY;
skb_record_rx_queue(skb, rxq->rspq.idx);
skb_mark_napi_id(skb, &rxq->rspq.napi);
if (rxq->rspq.netdev->features & NETIF_F_RXHASH)
skb_set_hash(skb, (__force u32)pkt->rsshdr.hash_val,
PKT_HASH_TYPE_L3);
......@@ -1763,6 +1767,7 @@ int t4_ethrx_handler(struct sge_rspq *q, const __be64 *rsp,
csum_ok = pkt->csum_calc && !pkt->err_vec &&
(q->netdev->features & NETIF_F_RXCSUM);
if ((pkt->l2info & htonl(RXF_TCP_F)) &&
!(cxgb_poll_busy_polling(q)) &&
(q->netdev->features & NETIF_F_GRO) && csum_ok && !pkt->ip_frag) {
do_gro(rxq, si, pkt);
return 0;
......@@ -1801,6 +1806,7 @@ int t4_ethrx_handler(struct sge_rspq *q, const __be64 *rsp,
__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), ntohs(pkt->vlan));
rxq->stats.vlan_ex++;
}
skb_mark_napi_id(skb, &q->napi);
netif_receive_skb(skb);
return 0;
}
......@@ -1963,6 +1969,38 @@ static int process_responses(struct sge_rspq *q, int budget)
return budget - budget_left;
}
#ifdef CONFIG_NET_RX_BUSY_POLL
int cxgb_busy_poll(struct napi_struct *napi)
{
struct sge_rspq *q = container_of(napi, struct sge_rspq, napi);
unsigned int params, work_done;
u32 val;
if (!cxgb_poll_lock_poll(q))
return LL_FLUSH_BUSY;
work_done = process_responses(q, 4);
params = QINTR_TIMER_IDX(TIMERREG_COUNTER0_X) | QINTR_CNT_EN;
q->next_intr_params = params;
val = CIDXINC_V(work_done) | SEINTARM_V(params);
/* If we don't have access to the new User GTS (T5+), use the old
* doorbell mechanism; otherwise use the new BAR2 mechanism.
*/
if (unlikely(!q->bar2_addr))
t4_write_reg(q->adap, MYPF_REG(SGE_PF_GTS_A),
val | INGRESSQID_V((u32)q->cntxt_id));
else {
writel(val | INGRESSQID_V(q->bar2_qid),
q->bar2_addr + SGE_UDB_GTS);
wmb();
}
cxgb_poll_unlock_poll(q);
return work_done;
}
#endif /* CONFIG_NET_RX_BUSY_POLL */
/**
* napi_rx_handler - the NAPI handler for Rx processing
* @napi: the napi instance
......@@ -1978,9 +2016,13 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
{
unsigned int params;
struct sge_rspq *q = container_of(napi, struct sge_rspq, napi);
int work_done = process_responses(q, budget);
int work_done;
u32 val;
if (!cxgb_poll_lock_napi(q))
return budget;
work_done = process_responses(q, budget);
if (likely(work_done < budget)) {
int timer_index;
......@@ -2018,6 +2060,7 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
q->bar2_addr + SGE_UDB_GTS);
wmb();
}
cxgb_poll_unlock_napi(q);
return work_done;
}
......@@ -2341,6 +2384,7 @@ int t4_sge_alloc_rxq(struct adapter *adap, struct sge_rspq *iq, bool fwevtq,
goto err;
netif_napi_add(dev, &iq->napi, napi_rx_handler, 64);
napi_hash_add(&iq->napi);
iq->cur_desc = iq->desc;
iq->cidx = 0;
iq->gen = 1;
......@@ -2598,6 +2642,7 @@ static void free_rspq_fl(struct adapter *adap, struct sge_rspq *rq,
rq->cntxt_id, fl_id, 0xffff);
dma_free_coherent(adap->pdev_dev, (rq->size + 1) * rq->iqe_len,
rq->desc, rq->phys_addr);
napi_hash_del(&rq->napi);
netif_napi_del(&rq->napi);
rq->netdev = NULL;
rq->cntxt_id = rq->abs_id = 0;
......
......@@ -59,6 +59,7 @@
/* GTS register */
#define SGE_TIMERREGS 6
#define TIMERREG_COUNTER0_X 0
/* T5 and later support a new BAR2-based doorbell mechanism for Egress Queues.
* The User Doorbells are each 128 bytes in length with a Simple Doorbell at
......
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