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IB/ipath: Use PIO buffer for RC ACKs

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This reduces the latency for RC ACKs when a PIO buffer is available.

Signed-off-by: Ralph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
This commit is contained in:
Ralph Campbell 2008-04-16 21:09:27 -07:00 committed by Roland Dreier
parent c4b4d16e09
commit d98b193776
1 changed files with 39 additions and 18 deletions
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57
drivers/infiniband/hw/ipath/ipath_rc.c
View file

@ -31,6 +31,8 @@
* SOFTWARE.
*/
#include <linux/io.h>
#include "ipath_verbs.h"
#include "ipath_kernel.h"
@ -585,19 +587,39 @@ bail:
static void send_rc_ack(struct ipath_qp *qp)
{
struct ipath_ibdev *dev = to_idev(qp->ibqp.device);
struct ipath_devdata *dd;
u16 lrh0;
u32 bth0;
u32 hwords;
u32 __iomem *piobuf;
struct ipath_ib_header hdr;
struct ipath_other_headers *ohdr;
unsigned long flags;
spin_lock_irqsave(&qp->s_lock, flags);
/* Don't send ACK or NAK if a RDMA read or atomic is pending. */
if (qp->r_head_ack_queue != qp->s_tail_ack_queue ||
(qp->s_flags & IPATH_S_ACK_PENDING) ||
qp->s_ack_state != OP(ACKNOWLEDGE))
goto queue_ack;
spin_unlock_irqrestore(&qp->s_lock, flags);
dd = dev->dd;
piobuf = ipath_getpiobuf(dd, 0, NULL);
if (!piobuf) {
/*
* We are out of PIO buffers at the moment.
* Pass responsibility for sending the ACK to the
* send tasklet so that when a PIO buffer becomes
* available, the ACK is sent ahead of other outgoing
* packets.
*/
spin_lock_irqsave(&qp->s_lock, flags);
goto queue_ack;
}
/* Construct the header. */
ohdr = &hdr.u.oth;
lrh0 = IPATH_LRH_BTH;
@ -611,7 +633,7 @@ static void send_rc_ack(struct ipath_qp *qp)
lrh0 = IPATH_LRH_GRH;
}
/* read pkey_index w/o lock (its atomic) */
bth0 = ipath_get_pkey(dev->dd, qp->s_pkey_index) |
bth0 = ipath_get_pkey(dd, qp->s_pkey_index) |
(OP(ACKNOWLEDGE) << 24) | (1 << 22);
if (qp->r_nak_state)
ohdr->u.aeth = cpu_to_be32((qp->r_msn & IPATH_MSN_MASK) |
@ -623,30 +645,29 @@ static void send_rc_ack(struct ipath_qp *qp)
hdr.lrh[0] = cpu_to_be16(lrh0);
hdr.lrh[1] = cpu_to_be16(qp->remote_ah_attr.dlid);
hdr.lrh[2] = cpu_to_be16(hwords + SIZE_OF_CRC);
hdr.lrh[3] = cpu_to_be16(dev->dd->ipath_lid);
hdr.lrh[3] = cpu_to_be16(dd->ipath_lid);
ohdr->bth[0] = cpu_to_be32(bth0);
ohdr->bth[1] = cpu_to_be32(qp->remote_qpn);
ohdr->bth[2] = cpu_to_be32(qp->r_ack_psn & IPATH_PSN_MASK);
/*
* If we can send the ACK, clear the ACK state.
*/
if (ipath_verbs_send(qp, &hdr, hwords, NULL, 0) == 0) {
dev->n_unicast_xmit++;
goto done;
}
writeq(hwords + 1, piobuf);
/*
* We are out of PIO buffers at the moment.
* Pass responsibility for sending the ACK to the
* send tasklet so that when a PIO buffer becomes
* available, the ACK is sent ahead of other outgoing
* packets.
*/
dev->n_rc_qacks++;
if (dd->ipath_flags & IPATH_PIO_FLUSH_WC) {
u32 *hdrp = (u32 *) &hdr;
ipath_flush_wc();
__iowrite32_copy(piobuf + 2, hdrp, hwords - 1);
ipath_flush_wc();
__raw_writel(hdrp[hwords - 1], piobuf + hwords + 1);
} else
__iowrite32_copy(piobuf + 2, (u32 *) &hdr, hwords);
ipath_flush_wc();
dev->n_unicast_xmit++;
goto done;
queue_ack:
spin_lock_irqsave(&qp->s_lock, flags);
dev->n_rc_qacks++;
qp->s_flags |= IPATH_S_ACK_PENDING;
qp->s_nak_state = qp->r_nak_state;