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RDS: Rewrite rds_send_xmit
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Simplify rds_send_xmit().

Send a congestion map (via xmit_cong_map) without
decrementing send_quota.

Move resetting of conn xmit variables to end of loop.

Update comments.

Implement a special case to turn off sending an rds header
when there is an atomic op and no other data.

Signed-off-by: Andy Grover <andy.grover@oracle.com>
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Andy Grover committed Sep 9, 2010
1 parent 6c7cc6e commit 5b2366b
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Showing 2 changed files with 73 additions and 63 deletions.
5 changes: 2 additions & 3 deletions net/rds/rds.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -96,8 +96,9 @@ struct rds_connection {
unsigned long c_xmit_sg;
unsigned int c_xmit_hdr_off;
unsigned int c_xmit_data_off;
unsigned int c_xmit_rdma_sent;
unsigned int c_xmit_atomic_sent;
unsigned int c_xmit_rdma_sent;
unsigned int c_xmit_data_sent;

spinlock_t c_lock; /* protect msg queues */
u64 c_next_tx_seq;
Expand All @@ -120,8 +121,6 @@ struct rds_connection {

struct list_head c_map_item;
unsigned long c_map_queued;
unsigned long c_map_offset;
unsigned long c_map_bytes;

unsigned int c_unacked_packets;
unsigned int c_unacked_bytes;
Expand Down
131 changes: 71 additions & 60 deletions net/rds/send.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -72,8 +72,9 @@ void rds_send_reset(struct rds_connection *conn)
conn->c_xmit_sg = 0;
conn->c_xmit_hdr_off = 0;
conn->c_xmit_data_off = 0;
conn->c_xmit_rdma_sent = 0;
conn->c_xmit_atomic_sent = 0;
conn->c_xmit_rdma_sent = 0;
conn->c_xmit_data_sent = 0;

conn->c_map_queued = 0;

Expand Down Expand Up @@ -137,69 +138,54 @@ int rds_send_xmit(struct rds_connection *conn)

/*
* spin trying to push headers and data down the connection until
* the connection doens't make forward progress.
* the connection doesn't make forward progress.
*/
while (--send_quota) {
/*
* See if need to send a congestion map update if we're
* between sending messages. The send_sem protects our sole
* use of c_map_offset and _bytes.
* Note this is used only by transports that define a special
* xmit_cong_map function. For all others, we create allocate
* a cong_map message and treat it just like any other send.
*/
if (conn->c_map_bytes) {
ret = conn->c_trans->xmit_cong_map(conn, conn->c_lcong,
conn->c_map_offset);
if (ret <= 0)
break;

conn->c_map_offset += ret;
conn->c_map_bytes -= ret;
if (conn->c_map_bytes)
continue;
}

/* If we're done sending the current message, clear the
* offset and S/G temporaries.
*/
rm = conn->c_xmit_rm;
if (rm &&
conn->c_xmit_hdr_off == sizeof(struct rds_header) &&
conn->c_xmit_sg == rm->data.op_nents) {
conn->c_xmit_rm = NULL;
conn->c_xmit_sg = 0;
conn->c_xmit_hdr_off = 0;
conn->c_xmit_data_off = 0;
conn->c_xmit_rdma_sent = 0;
conn->c_xmit_atomic_sent = 0;

/* Release the reference to the previous message. */
rds_message_put(rm);
rm = NULL;
}

/* If we're asked to send a cong map update, do so.
/*
* If between sending messages, we can send a pending congestion
* map update.
*
* Transports either define a special xmit_cong_map function,
* or we allocate a cong_map message and treat it just like any
* other send.
*/
if (!rm && test_and_clear_bit(0, &conn->c_map_queued)) {
if (conn->c_trans->xmit_cong_map) {
conn->c_map_offset = 0;
conn->c_map_bytes = sizeof(struct rds_header) +
unsigned long map_offset = 0;
unsigned long map_bytes = sizeof(struct rds_header) +
RDS_CONG_MAP_BYTES;
continue;
}

rm = rds_cong_update_alloc(conn);
if (IS_ERR(rm)) {
ret = PTR_ERR(rm);
break;
}
while (map_bytes) {
ret = conn->c_trans->xmit_cong_map(conn, conn->c_lcong,
map_offset);
if (ret <= 0) {
/* too far down the rabbithole! */
mutex_unlock(&conn->c_send_lock);
rds_conn_error(conn, "Cong map xmit failed\n");
goto out;
}

map_offset += ret;
map_bytes -= ret;
}
} else {
/* send cong update like a normal rm */
rm = rds_cong_update_alloc(conn);
if (IS_ERR(rm)) {
ret = PTR_ERR(rm);
break;
}
rm->data.op_active = 1;

conn->c_xmit_rm = rm;
conn->c_xmit_rm = rm;
}
}

/*
* Grab the next message from the send queue, if there is one.
* If not already working on one, grab the next message.
*
* c_xmit_rm holds a ref while we're sending this message down
* the connction. We can use this ref while holding the
Expand Down Expand Up @@ -264,7 +250,6 @@ int rds_send_xmit(struct rds_connection *conn)
conn->c_xmit_rm = rm;
}


if (rm->atomic.op_active && !conn->c_xmit_atomic_sent) {
ret = conn->c_trans->xmit_atomic(conn, rm);
if (ret)
Expand All @@ -273,13 +258,20 @@ int rds_send_xmit(struct rds_connection *conn)
/* The transport owns the mapped memory for now.
* You can't unmap it while it's on the send queue */
set_bit(RDS_MSG_MAPPED, &rm->m_flags);

/*
* This is evil, muahaha.
* We permit 0-byte sends. (rds-ping depends on this.)
* BUT if there is an atomic op and no sent data,
* we turn off sending the header, to achieve
* "silent" atomics.
* But see below; RDMA op might toggle this back on!
*/
if (rm->data.op_nents == 0)
rm->data.op_active = 0;
}

/*
* Try and send an rdma message. Let's see if we can
* keep this simple and require that the transport either
* send the whole rdma or none of it.
*/
/* The transport either sends the whole rdma or none of it */
if (rm->rdma.op_active && !conn->c_xmit_rdma_sent) {
ret = conn->c_trans->xmit_rdma(conn, &rm->rdma);
if (ret)
Expand All @@ -294,9 +286,7 @@ int rds_send_xmit(struct rds_connection *conn)
set_bit(RDS_MSG_MAPPED, &rm->m_flags);
}

if (rm->data.op_active
&& (conn->c_xmit_hdr_off < sizeof(struct rds_header) ||
conn->c_xmit_sg < rm->data.op_nents)) {
if (rm->data.op_active && !conn->c_xmit_data_sent) {
ret = conn->c_trans->xmit(conn, rm,
conn->c_xmit_hdr_off,
conn->c_xmit_sg,
Expand Down Expand Up @@ -326,6 +316,27 @@ int rds_send_xmit(struct rds_connection *conn)
conn->c_xmit_sg == rm->data.op_nents);
}
}

if (conn->c_xmit_hdr_off == sizeof(struct rds_header) &&
(conn->c_xmit_sg == rm->data.op_nents))
conn->c_xmit_data_sent = 1;
}

/*
* A rm will only take multiple times through this loop
* if there is a data op. Thus, if the data is sent (or there was
* none), then we're done with the rm.
*/
if (!rm->data.op_active || conn->c_xmit_data_sent) {
conn->c_xmit_rm = NULL;
conn->c_xmit_sg = 0;
conn->c_xmit_hdr_off = 0;
conn->c_xmit_data_off = 0;
conn->c_xmit_rdma_sent = 0;
conn->c_xmit_atomic_sent = 0;
conn->c_xmit_data_sent = 0;

rds_message_put(rm);
}
}

Expand All @@ -350,7 +361,7 @@ int rds_send_xmit(struct rds_connection *conn)
*/
mutex_unlock(&conn->c_send_lock);

if (conn->c_map_bytes || (send_quota == 0 && !was_empty)) {
if (send_quota == 0 && !was_empty) {
/* We exhausted the send quota, but there's work left to
* do. Return and (re-)schedule the send worker.
*/
Expand Down

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