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homa_incoming.c
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/* Copyright (c) 2019-2021 Stanford University
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* This file contains functions that handle incoming Homa messages, including
* both receiving information for those messages and sending grants. */
#include "homa_impl.h"
/**
* homa_message_in_init() - Constructor for homa_message_in.
* @msgin: Structure to initialize.
* @length: Total number of bytes in message.
* @incoming: Initial bytes of message that the sender is already
* planning to transmit, even without grants.
*/
void homa_message_in_init(struct homa_message_in *msgin, int length,
int incoming)
{
msgin->total_length = length;
skb_queue_head_init(&msgin->packets);
msgin->num_skbs = 0;
msgin->bytes_remaining = length;
msgin->incoming = incoming;
if (msgin->incoming > msgin->total_length)
msgin->incoming = msgin->total_length;
msgin->extra_incoming = 0;
msgin->priority = 0;
msgin->scheduled = length > incoming;
msgin->possibly_in_grant_queue = msgin->scheduled;
msgin->xfer_offset = 0;
msgin->xfer_skb = NULL;
if (length < HOMA_NUM_SMALL_COUNTS*64) {
INC_METRIC(small_msg_bytes[(length-1) >> 6], length);
} else if (length < HOMA_NUM_MEDIUM_COUNTS*1024) {
INC_METRIC(medium_msg_bytes[(length-1) >> 10], length);
} else {
INC_METRIC(large_msg_count, 1);
INC_METRIC(large_msg_bytes, length);
}
}
/**
* homa_message_in_destroy() - Destructor for homa_message_in.
* @msgin: Structure to clean up.
*/
void homa_message_in_destroy(struct homa_message_in *msgin)
{
struct sk_buff *skb, *next;
if (msgin->total_length < 0)
return;
skb_queue_walk_safe(&msgin->packets, skb, next)
kfree_skb(skb);
__skb_queue_head_init(&msgin->packets);
msgin->total_length = -1;
}
/**
* homa_add_packet() - Add an incoming packet to the contents of a
* partially received message.
* @rpc: Add the packet to the msgin for this RPC.
* @skb: The new packet. This function takes ownership of the packet
* and will free it, if it doesn't get added to msgin (because
* it provides no new data).
*/
void homa_add_packet(struct homa_rpc *rpc, struct sk_buff *skb)
{
struct data_header *h = (struct data_header *) skb->data;
int offset = ntohl(h->seg.offset);
int data_bytes = ntohl(h->seg.segment_length);
struct sk_buff *skb2;
/* Any data from the packet with offset less than this is
* of no value.*/
int floor = 0;
/* Any data with offset >= this is useless. */
int ceiling = rpc->msgin.total_length;
/* Figure out where in the list of existing packets to insert the
* new one. It doesn't necessarily go at the end, but it almost
* always will in practice, so work backwards from the end of the
* list.
*/
skb_queue_reverse_walk(&rpc->msgin.packets, skb2) {
struct data_header *h2 = (struct data_header *) skb2->data;
int offset2 = ntohl(h2->seg.offset);
int data_bytes2 = skb2->len - sizeof32(struct data_header);
if (offset2 < offset) {
floor = offset2 + data_bytes2;
break;
}
ceiling = offset2;
}
/* New packet goes right after skb2 (which may refer to the header).
* Packets shouldn't overlap in byte ranges, but the code below
* assumes they might, so it computes how many non-overlapping bytes
* are contributed by the new packet.
*/
if (unlikely(floor < offset)) {
floor = offset;
}
if (ceiling > offset + data_bytes) {
ceiling = offset + data_bytes;
}
if (floor >= ceiling) {
/* This packet is redundant. */
// char buffer[100];
// printk(KERN_NOTICE "redundant Homa packet: %s\n",
// homa_print_packet(skb, buffer, sizeof(buffer)));
INC_METRIC(redundant_packets, 1);
kfree_skb(skb);
return;
}
if (h->retransmit) {
INC_METRIC(resent_packets_used, 1);
homa_freeze(rpc, PACKET_LOST, "Freezing because of lost "
"packet, id %d, peer 0x%x");
}
__skb_insert(skb, skb2, skb2->next, &rpc->msgin.packets);
rpc->msgin.bytes_remaining -= (ceiling - floor);
rpc->msgin.num_skbs++;
}
/**
* homa_message_in_copy_data() - Extract data from an incoming message
* and copy it to buffer(s) in user space. If one call does not extract
* the entire message, the function can be called again to extract the
* next bytes.
* @msgin: The message whose data should be extracted.
* @iter: Describes the available buffer space at user-level; message
* data gets copied here.
* @max_bytes: Total number of bytes of data to extract.
*
* Return: The number of bytes copied, or a negative errno.
*/
int homa_message_in_copy_data(struct homa_message_in *msgin,
struct iov_iter *iter, int max_bytes)
{
int err;
int remaining = max_bytes;
/* Do the right thing even if packets have overlapping ranges.
* In practice, this shouldn't ever be necessary.
*/
if (msgin->xfer_offset == 0)
msgin->xfer_skb = msgin->packets.next;
skb_queue_walk_from(&msgin->packets, msgin->xfer_skb) {
struct data_header *h =
(struct data_header *) msgin->xfer_skb->data;
int this_offset = ntohl(h->seg.offset);
int this_size = ntohl(h->seg.segment_length);
if (msgin->xfer_offset != this_offset) {
BUG_ON(msgin->xfer_offset < this_offset);
this_size -= (msgin->xfer_offset - this_offset);
}
if (this_size > remaining)
this_size = remaining;
if (unlikely(this_size <= 0))
continue;
err = skb_copy_datagram_iter(msgin->xfer_skb,
sizeof(*h) + (msgin->xfer_offset - this_offset),
iter, this_size);
if (err) {
return err;
}
remaining -= this_size;
msgin->xfer_offset += this_size;
if (remaining == 0) {
break;
}
}
return max_bytes - remaining;
}
/**
* homa_get_resend_range() - Given a message for which some input data
* is missing, find the first range of missing data.
* @msgin: Message for which not all granted data has been received.
* @resend: The @offset and @length fields of this structure will be
* filled in with information about the first missing range
* in @msgin.
*/
void homa_get_resend_range(struct homa_message_in *msgin,
struct resend_header *resend)
{
struct sk_buff *skb;
int missing_bytes;
/* This will eventually be the top of the first missing range. */
int end_offset;
if (msgin->total_length < 0) {
/* Haven't received any data for this message; request
* retransmission of just the first packet (the sender
* will send at least one full packet, regardless of
* the length below).
*/
resend->offset = 0;
resend->length = htonl(100);
return;
}
missing_bytes = msgin->bytes_remaining
- (msgin->total_length - msgin->incoming);
if (missing_bytes == 0) {
resend->offset = 0;
resend->length = 0;
return;
}
end_offset = msgin->incoming;
/* Basic idea: walk backwards through the message's packets until
* we have accounted for all missing bytes; this will identify
* the first missing range.
*/
skb_queue_reverse_walk(&msgin->packets, skb) {
struct data_header *h = (struct data_header *) skb->data;
int offset = ntohl(h->seg.offset);
int pkt_length = ntohl(h->seg.segment_length);
int gap;
if (pkt_length > (msgin->total_length - offset))
pkt_length = msgin->total_length - offset;
gap = end_offset - (offset + pkt_length);
missing_bytes -= gap;
if (missing_bytes == 0) {
resend->offset = htonl(offset + pkt_length);
resend->length = htonl(gap);
return;
}
end_offset = offset;
}
/* The first packet(s) are missing. */
resend->offset = 0;
resend->length = htonl(missing_bytes);
}
/**
* homa_pkt_dispatch() - Top-level function for handling an incoming packet.
* @skb: The incoming packet. This function takes ownership of the
* packet and will ensure that it is eventually freed.
* @hsk: Homa socket that owns the packet's destination port. This socket
* is not locked, but its existence is ensured for the life
* of this method.
*
* Return: None.
*/
void homa_pkt_dispatch(struct sk_buff *skb, struct homa_sock *hsk)
{
struct common_header *h = (struct common_header *) skb->data;
struct homa_rpc *rpc;
__u64 id = homa_local_id(h->sender_id);
/* If there is an ack in the packet, handle it. Must do this
* before locking the packet's RPC, since we may need to acquire
* (other) RPC locks to handle the acks.
*/
if (h->type == DATA) {
struct data_header *dh = (struct data_header *) h;
if (dh->seg.ack.client_id != 0)
homa_rpc_acked(hsk, ip_hdr(skb)->saddr, &dh->seg.ack);
}
/* Find and lock the RPC for this packet. */
if (!homa_is_client(id)) {
/* We are the server for this RPC. */
if (h->type == DATA) {
/* Create a new RPC if one doesn't already exist. */
rpc = homa_rpc_new_server(hsk, ip_hdr(skb)->saddr,
(struct data_header *) h);
if (IS_ERR(rpc)) {
printk(KERN_WARNING "homa_pkt_dispatch "
"couldn't create server rpc: "
"error %lu",
-PTR_ERR(rpc));
INC_METRIC(server_cant_create_rpcs, 1);
rpc = NULL;
goto discard;
}
} else
rpc = homa_find_server_rpc(hsk, ip_hdr(skb)->saddr,
ntohs(h->sport), id);
} else {
rpc = homa_find_client_rpc(hsk, id);
}
if (unlikely(rpc == NULL)) {
if ((h->type != CUTOFFS) && (h->type != NEED_ACK)
&& (h->type != ACK) && (h->type != RESEND)) {
tt_record4("Discarding packet for unknown RPC, id %u, "
"type %d, peer 0x%x:%d",
id, h->type,
ntohl(ip_hdr(skb)->saddr),
ntohs(h->sport));
if ((h->type != GRANT) || homa_is_client(id))
INC_METRIC(unknown_rpcs, 1);
goto discard;
}
} else {
if ((h->type == DATA) || (h->type == GRANT)
|| (h->type == BUSY))
rpc->silent_ticks = 0;
rpc->peer->outstanding_resends = 0;
}
switch (h->type) {
case DATA:
if (homa_data_pkt(skb, rpc) != 0)
return;
INC_METRIC(packets_received[DATA - DATA], 1);
if (hsk->dead_skbs >= 2*hsk->homa->dead_buffs_limit) {
/* We get here if neither homa_wait_for_message
* nor homa_timer can keep up with reaping dead
* RPCs. See reap.txt for details.
*/
uint64_t start = get_cycles();
tt_record("homa_data_pkt calling homa_rpc_reap");
homa_rpc_reap(hsk, hsk->homa->reap_limit);
INC_METRIC(data_pkt_reap_cycles, get_cycles() - start);
}
break;
case GRANT:
INC_METRIC(packets_received[GRANT - DATA], 1);
homa_grant_pkt(skb, rpc);
break;
case RESEND:
INC_METRIC(packets_received[RESEND - DATA], 1);
homa_resend_pkt(skb, rpc, hsk);
break;
case UNKNOWN:
INC_METRIC(packets_received[UNKNOWN - DATA], 1);
homa_unknown_pkt(skb, rpc);
break;
case BUSY:
INC_METRIC(packets_received[BUSY - DATA], 1);
tt_record2("received BUSY for id %d, peer 0x%x",
id, ntohl(rpc->peer->addr));
/* Nothing to do for these packets except reset silent_ticks,
* which happened above.
*/
goto discard;
case CUTOFFS:
INC_METRIC(packets_received[CUTOFFS - DATA], 1);
homa_cutoffs_pkt(skb, hsk);
break;
case NEED_ACK:
INC_METRIC(packets_received[NEED_ACK - DATA], 1);
homa_need_ack_pkt(skb, hsk, rpc);
break;
case ACK:
INC_METRIC(packets_received[ACK - DATA], 1);
homa_ack_pkt(skb, hsk, rpc);
rpc = NULL;
break;
default:
INC_METRIC(unknown_packet_types, 1);
goto discard;
}
goto done;
discard:
kfree_skb(skb);
done:
if (rpc)
homa_rpc_unlock(rpc);
}
/**
* homa_data_pkt() - Handler for incoming DATA packets
* @skb: Incoming packet; size known to be large enough for the header.
* This function now owns the packet.
* @rpc: Information about the RPC corresponding to this packet.
*
* Return: Zero means the function completed successfully. Nonzero means
* that the RPC had to be unlocked and deleted because the socket has been
* shut down; the caller should not access the RPC anymore. Note: this method
* may change the RPC's state to RPC_READY.
*/
int homa_data_pkt(struct sk_buff *skb, struct homa_rpc *rpc)
{
struct homa *homa = rpc->hsk->homa;
struct data_header *h = (struct data_header *) skb->data;
int incoming = ntohl(h->incoming);
tt_record4("incoming data packet, id %d, peer 0x%x, offset %d/%d",
homa_local_id(h->common.sender_id),
ntohl(rpc->peer->addr), ntohl(h->seg.offset),
ntohl(h->message_length));
if (rpc->state != RPC_INCOMING) {
if (unlikely(!homa_is_client(rpc->id)
|| (rpc->state == RPC_READY))) {
kfree_skb(skb);
return 0;
}
homa_message_in_init(&rpc->msgin, ntohl(h->message_length),
incoming);
INC_METRIC(responses_received, 1);
rpc->state = RPC_INCOMING;
}
homa_add_packet(rpc, skb);
if (rpc->msgin.scheduled) {
homa_check_grantable(homa, rpc);
} else if (!rpc->msgin.extra_incoming && rpc->msgin.bytes_remaining) {
rpc->msgin.extra_incoming = rpc->msgin.bytes_remaining;
atomic_add(rpc->msgin.bytes_remaining, &homa->extra_incoming);
}
if (rpc->active_links.next == LIST_POISON1) {
/* This is the first packet of a server RPC, so we have to
* add the RPC to @hsk->active_rpcs. We do it here, rather
* than in homa_rpc_new_server, so we can acquire the socket
* lock just once to both add the RPC to active_rpcs and
* also add the RPC to the ready list, if appropriate.
*/
INC_METRIC(requests_received, 1);
homa_sock_lock(rpc->hsk, "homa_data_pkt (first)");
if (rpc->hsk->shutdown) {
/* Unsafe to add new RPCs to a socket after shutdown
* has begun; destroy the new RPC.
*/
homa_message_in_destroy(&rpc->msgin);
homa_sock_unlock(rpc->hsk);
homa_rpc_unlock(rpc);
kfree(rpc);
return 1;
}
list_add_tail_rcu(&rpc->active_links, &rpc->hsk->active_rpcs);
if (rpc->msgin.bytes_remaining == 0)
homa_rpc_ready(rpc);
homa_sock_unlock(rpc->hsk);
} else {
if (rpc->msgin.bytes_remaining == 0) {
homa_remove_from_grantable(homa, rpc);
homa_sock_lock(rpc->hsk, "homa_data_pkt (not first)");
if (!rpc->hsk->shutdown)
homa_rpc_ready(rpc);
homa_sock_unlock(rpc->hsk);
}
}
if (ntohs(h->cutoff_version) != homa->cutoff_version) {
/* The sender has out-of-date cutoffs. Note: we may need
* to resend CUTOFFS packets if one gets lost, but we don't
* want to send multiple CUTOFFS packets when a stream of
* packets arrives with stale cutoff_versions. Thus, we
* don't send CUTOFFS unless there is a version mismatch
* *and* it is been a while since the previous CUTOFFS
* packet.
*/
if (jiffies != rpc->peer->last_update_jiffies) {
struct cutoffs_header h2;
int i;
for (i = 0; i < HOMA_MAX_PRIORITIES; i++) {
h2.unsched_cutoffs[i] =
htonl(homa->unsched_cutoffs[i]);
}
h2.cutoff_version = htons(homa->cutoff_version);
homa_xmit_control(CUTOFFS, &h2, sizeof(h2), rpc);
rpc->peer->last_update_jiffies = jiffies;
}
}
return 0;
}
/**
* homa_grant_pkt() - Handler for incoming GRANT packets
* @skb: Incoming packet; size already verified large enough for header.
* This function now owns the packet.
* @rpc: Information about the RPC corresponding to this packet.
*/
void homa_grant_pkt(struct sk_buff *skb, struct homa_rpc *rpc)
{
struct grant_header *h = (struct grant_header *) skb->data;
tt_record3("processing grant for id %llu, offset %d, priority %d",
homa_local_id(h->common.sender_id), ntohl(h->offset),
h->priority);
if (rpc->state == RPC_OUTGOING) {
int new_offset = ntohl(h->offset);
if (new_offset > rpc->msgout.granted) {
rpc->msgout.granted = new_offset;
if (new_offset > rpc->msgout.length)
rpc->msgout.granted = rpc->msgout.length;
}
rpc->msgout.sched_priority = h->priority;
homa_xmit_data(rpc, false);
}
kfree_skb(skb);
}
/**
* homa_resend_pkt() - Handler for incoming RESEND packets
* @skb: Incoming packet; size already verified large enough for header.
* This function now owns the packet.
* @rpc: Information about the RPC corresponding to this packet; must
* be locked by caller, but may be NULL if there is no RPC matching
* this packet
* @hsk: Socket on which the packet was received.
*/
void homa_resend_pkt(struct sk_buff *skb, struct homa_rpc *rpc,
struct homa_sock *hsk)
{
struct resend_header *h = (struct resend_header *) skb->data;
struct busy_header busy;
if (rpc == NULL) {
tt_record4("resend request for unknown id %d, peer 0x%x:%d, "
"offset %d; responding with UNKNOWN",
homa_local_id(h->common.sender_id),
ntohl(ip_hdr(skb)->saddr),
ntohs(h->common.sport),
ntohl(h->offset));
homa_xmit_unknown(skb, hsk);
goto done;
}
tt_record4("resend request for id %llu, offset %d, length %d, prio %d",
rpc->id, ntohl(h->offset), ntohl(h->length),
h->priority);
if (!homa_is_client(rpc->id)) {
/* We are the server for this RPC. */
if (rpc->state != RPC_OUTGOING) {
tt_record2("sending BUSY from resend, id %d, state %d",
rpc->id, rpc->state);
homa_xmit_control(BUSY, &busy, sizeof(busy), rpc);
goto done;
}
}
if (rpc->msgout.next_packet && (homa_data_offset(rpc->msgout.next_packet)
< rpc->msgout.granted)) {
/* We have chosen not to transmit data from this message;
* send BUSY instead.
*/
tt_record3("sending BUSY from resend, id %d, offset %d, "
"granted %d", rpc->id,
homa_data_offset(rpc->msgout.next_packet),
rpc->msgout.granted);
homa_xmit_control(BUSY, &busy, sizeof(busy), rpc);
} else {
if (ntohl(h->length) == 0) {
/* This RESEND is from a server just trying to determine
* whether the client still cares about the RPC; return
* BUSY so the server doesn't time us out.
*/
homa_xmit_control(BUSY, &busy, sizeof(busy), rpc);
}
homa_resend_data(rpc, ntohl(h->offset),
ntohl(h->offset) + ntohl(h->length),
h->priority);
}
done:
kfree_skb(skb);
}
/**
* homa_unknown_pkt() - Handler for incoming UNKNOWN packets.
* @skb: Incoming packet; size known to be large enough for the header.
* This function now owns the packet.
* @rpc: Information about the RPC corresponding to this packet.
*/
void homa_unknown_pkt(struct sk_buff *skb, struct homa_rpc *rpc)
{
tt_record3("Received unknown for id %llu, peer %x:%d",
rpc->id, ntohl(rpc->peer->addr), rpc->dport);
if (homa_is_client(rpc->id)) {
if ((rpc->state == RPC_READY) || (rpc->state == RPC_DEAD)) {
/* The missing data packets apparently arrived while
* the UNKNOWN was being transmitted.
*/
goto done;
}
if (rpc->state == RPC_OUTGOING) {
/* It appears that everything we've already transmitted
* has been lost; retransmit it.
*/
tt_record4("Restarting id %d to server 0x%x:%d, "
"lost %d bytes",
rpc->id, ntohl(rpc->peer->addr),
rpc->dport,
homa_rpc_send_offset(rpc));
homa_freeze(rpc, RESTART_RPC, "Freezing because of "
"RPC restart, id %d, peer 0x%x");
homa_resend_data(rpc, 0, homa_rpc_send_offset(rpc),
homa_unsched_priority(rpc->hsk->homa,
rpc->peer, rpc->msgout.length));
goto done;
}
printk(KERN_ERR "Received unknown for RPC id %llu, peer %s:%d "
"in bogus state %d; discarding unknown\n",
rpc->id, homa_print_ipv4_addr(rpc->peer->addr),
rpc->dport, rpc->state);
tt_record4("Discarding unknown for RPC id %d, peer 0x%x:%d: "
"bad state %d",
rpc->id, ntohl(rpc->peer->addr), rpc->dport,
rpc->state);
} else {
if (rpc->hsk->homa->verbose)
printk(KERN_NOTICE "Freeing rpc id %llu from client "
"%s:%d: unknown to client",
rpc->id,
homa_print_ipv4_addr(rpc->peer->addr),
rpc->dport);
homa_rpc_free(rpc);
INC_METRIC(server_rpcs_unknown, 1);
}
done:
kfree_skb(skb);
}
/**
* homa_cutoffs_pkt() - Handler for incoming CUTOFFS packets
* @skb: Incoming packet; size already verified large enough for header.
* This function now owns the packet.
* @hsk: Socket on which the packet was received.
*/
void homa_cutoffs_pkt(struct sk_buff *skb, struct homa_sock *hsk)
{
int i;
struct cutoffs_header *h = (struct cutoffs_header *) skb->data;
struct homa_peer *peer = homa_peer_find(&hsk->homa->peers,
ip_hdr(skb)->saddr, &hsk->inet);
if (!IS_ERR(peer)) {
peer->unsched_cutoffs[0] = INT_MAX;
for (i = 1; i <HOMA_MAX_PRIORITIES; i++)
peer->unsched_cutoffs[i] = ntohl(h->unsched_cutoffs[i]);
peer->cutoff_version = h->cutoff_version;
}
kfree_skb(skb);
}
/**
* homa_need_ack_pkt() - Handler for incoming NEED_ACK packets
* @skb: Incoming packet; size already verified large enough for header.
* This function now owns the packet.
* @hsk: Socket on which the packet was received.
* @rpc: The RPC named in the packet header, or NULL if no such
* RPC exists. The RPC has been locked by the caller.
*/
void homa_need_ack_pkt(struct sk_buff *skb, struct homa_sock *hsk,
struct homa_rpc *rpc)
{
struct common_header *h = (struct common_header *) skb->data;
struct ack_header ack;
struct homa_peer *peer;
/* Return if it's not safe for the peer to purge its state
* for this RPC, or if we can't find peer info.
*/
if (rpc != NULL) {
if (rpc->state != RPC_READY) {
tt_record4("Ignoring NEED_ACK for id %d, peer 0x%x,"
"state %d, bytes_remaining %d",
rpc->id, ntohl(rpc->peer->addr),
rpc->state, rpc->msgin.bytes_remaining);
goto done;
}
peer = rpc->peer;
} else {
peer = homa_peer_find(&hsk->homa->peers, ip_hdr(skb)->saddr,
&hsk->inet);
if (IS_ERR(peer))
goto done;
}
/* Send an ACK for this RPC. At the same time, include all of the
* other acks available for the peer. Note: can't use rpc below,
* since it may be NULL.
*/
ack.common.type = ACK;
ack.common.sport = h->dport;
ack.common.dport = h->sport;
ack.common.sender_id = be64_to_cpu(homa_local_id(h->sender_id));
ack.num_acks = htons(homa_peer_get_acks(peer,
NUM_PEER_UNACKED_IDS, ack.acks));
__homa_xmit_control(&ack, sizeof(ack), peer, hsk);
tt_record3("Responded to NEED_ACK for id %d, peer %0x%x with %d "
"other acks", homa_local_id(h->sender_id),
ntohl(ip_hdr(skb)->saddr), ntohs(ack.num_acks));
done:
kfree_skb(skb);
}
/**
* homa_ack_pkt() - Handler for incoming ACK packets
* @skb: Incoming packet; size already verified large enough for header.
* This function now owns the packet.
* @hsk: Socket on which the packet was received.
* @rpc: The RPC named in the packet header, or NULL if no such
* RPC exists. The RPC has been locked by the caller; this
* method takes ownership of the RPC and both frees and unlocks it.
*/
void homa_ack_pkt(struct sk_buff *skb, struct homa_sock *hsk,
struct homa_rpc *rpc)
{
struct ack_header *h = (struct ack_header *) skb->data;
int i, count;
if (rpc != NULL) {
homa_rpc_free(rpc);
/* It's awkward to unlock the RPC here, since we didn't
* lock it, but this is necessary because homa_rpc_acked
* may lock additional RPCs below and it isn't safe to hold
* multiple RPC locks at once.
*/
homa_rpc_unlock(rpc);
}
count = ntohs(h->num_acks);
for (i = 0; i < count; i++)
homa_rpc_acked(hsk, ip_hdr(skb)->saddr, &h->acks[i]);
tt_record3("ACK received for id %d, peer 0x%x, with %d other acks",
homa_local_id(h->common.sender_id),
ntohl(ip_hdr(skb)->saddr), count);
kfree_skb(skb);
}
/**
* homa_check_grantable() - This function ensures that an RPC is on a
* grantable list if appropriate, and not on one otherwise. It also adjusts
* the position of the RPC upward on its list, if needed.
* @homa: Overall data about the Homa protocol implementation.
* @rpc: RPC to check; typically the status of this RPC has changed
* in a way that may affect its grantability (e.g. a packet
* just arrived for it). Must be locked.
*/
void homa_check_grantable(struct homa *homa, struct homa_rpc *rpc)
{
struct homa_rpc *candidate;
struct homa_peer *peer = rpc->peer;
struct homa_peer *peer_cand;
struct homa_message_in *msgin = &rpc->msgin;
/* No need to do anything unless this message is ready for more
* grants.
*/
if (((rpc->msgin.incoming - (rpc->msgin.total_length
- rpc->msgin.bytes_remaining)) >= homa->rtt_bytes)
|| (rpc->msgin.incoming >= rpc->msgin.total_length))
return;
homa_grantable_lock(homa);
/* Note: must check incoming again: it might have changed. */
if ((rpc->state == RPC_DEAD) || (rpc->msgin.incoming
>= rpc->msgin.total_length)) {
homa_grantable_unlock(homa);
return;
}
/* Make sure this message is in the right place in the grantable_rpcs
* list for its peer.
*/
if (list_empty(&rpc->grantable_links)) {
/* Message not yet tracked; add it in priority order to
* the peer's list.
*/
rpc->msgin.birth = get_cycles();
list_for_each_entry(candidate, &peer->grantable_rpcs,
grantable_links) {
if (candidate->msgin.bytes_remaining
> msgin->bytes_remaining) {
list_add_tail(&rpc->grantable_links,
&candidate->grantable_links);
goto position_peer;
}
}
list_add_tail(&rpc->grantable_links, &peer->grantable_rpcs);
} else while (rpc != list_first_entry(&peer->grantable_rpcs,
struct homa_rpc, grantable_links)) {
/* Message is on the list, but its priority may have
* increased because of the recent packet arrival. If so,
* adjust its position in the list.
*/
candidate = list_prev_entry(rpc, grantable_links);
if (candidate->msgin.bytes_remaining <= msgin->bytes_remaining)
goto position_peer;
__list_del_entry(&candidate->grantable_links);
list_add(&candidate->grantable_links, &rpc->grantable_links);
}
position_peer:
/* At this point rpc is positioned correctly on the list for its peer.
* However, the peer may need to be added to, or moved upward on,
* homa->grantable_peers.
*/
if (list_empty(&peer->grantable_links)) {
/* Must add peer to the overall Homa list. */
homa->num_grantable_peers++;
list_for_each_entry(peer_cand, &homa->grantable_peers,
grantable_links) {
candidate = list_first_entry(&peer_cand->grantable_rpcs,
struct homa_rpc, grantable_links);
if (candidate->msgin.bytes_remaining
> msgin->bytes_remaining) {
list_add_tail(&peer->grantable_links,
&peer_cand->grantable_links);
goto done;
}
}
list_add_tail(&peer->grantable_links, &homa->grantable_peers);
goto done;
}
/* The peer is on Homa's list, but it may need to move upward. */
while (peer != list_first_entry(&homa->grantable_peers,
struct homa_peer, grantable_links)) {
struct homa_peer *prev_peer = list_prev_entry(
peer, grantable_links);
candidate = list_first_entry(&prev_peer->grantable_rpcs,
struct homa_rpc, grantable_links);
if (candidate->msgin.bytes_remaining <= msgin->bytes_remaining)
goto done;
__list_del_entry(&prev_peer->grantable_links);
list_add(&prev_peer->grantable_links, &peer->grantable_links);
}
done:
homa_grantable_unlock(homa);
}
/**
* homa_send_grants() - This function checks to see whether it is
* appropriate to send grants and, if so, it sends them.
* @homa: Overall data about the Homa protocol implementation.
*/
void homa_send_grants(struct homa *homa)
{
/* The overall goal is to keep homa->max_incoming bytes of data on
* their way to us at any given time. Ideally, each message should use
* a different priority level, determined by bytes_remaining (fewest
* bytes_remaining gets the highest priority). If there aren't enough
* scheduled priority levels for all of the messages, then the lowest
* level gets shared by multiple messages. If there are fewer messages
* than priority levels, then we use the lowest available levels
* (new higher-priority messages can use the higher levels to achieve
* instantaneous preemption).
*/
struct homa_rpc *candidate;
struct homa_peer *peer, *temp;
int rank, i;
__u64 start;
/* The variables below keep track of grants we need to send;
* don't send any until the very end, and release the lock
* first.
*/
/* How many more bytes of incoming are available below the limit. */
int available = homa->max_incoming - atomic_read(&homa->extra_incoming);
#ifdef __UNIT_TEST__
extern int mock_max_grants;
#define MAX_GRANTS mock_max_grants
#else
#define MAX_GRANTS 10
#endif
struct grant_header grants[MAX_GRANTS];
struct homa_rpc *rpcs[MAX_GRANTS];
int num_grants = 0;
/* Make a local copy of homa->grantable_peers, since that variable
* could change during this function.
*/
int num_grantable_peers = homa->num_grantable_peers;
if (list_empty(&homa->grantable_peers))
return;
start = get_cycles();
homa_grantable_lock(homa);
/* See if there are any messages that deserve a grant (they have
* fewer than homa->rtt_bytes of data in transit). Consider only
* a single (highest-priority) entry for each peer.
*/
rank = 0;
list_for_each_entry_safe(peer, temp, &homa->grantable_peers,
grantable_links) {
int extra_levels, priority;
int received, new_grant, on_the_way;
int old_incoming;
struct grant_header *grant;
rank++;
candidate = list_first_entry(&peer->grantable_rpcs,
struct homa_rpc, grantable_links);
/* Invariant: candidate msgin's incoming < total_length
* (otherwise it won't be on this list).
*/
received = (candidate->msgin.total_length
- candidate->msgin.bytes_remaining);
on_the_way = candidate->msgin.incoming - received;
available -= on_the_way;
if (on_the_way >= homa->grant_threshold)
continue;
old_incoming = candidate->msgin.incoming;
new_grant = old_incoming + homa->grant_increment;
if ((received + homa->rtt_bytes) > new_grant)
new_grant = received + homa->rtt_bytes;
if (new_grant > candidate->msgin.total_length)
new_grant = candidate->msgin.total_length;
available -= new_grant - candidate->msgin.incoming;
if (available < 0)
break;
/* The following line is needed to prevent spurious resends.
* Without it, if the timer fires right after we send the
* grant, it might think the RPC is slow and request a
* resend (until we send the grant, timeouts won't occur
* because there's no granted data).
*/
candidate->silent_ticks = 0;
/* Send a grant for this message. */
candidate->msgin.incoming = new_grant;
homa->grant_nonfifo_left -= (new_grant - old_incoming);
atomic_inc(&candidate->grants_in_progress);
rpcs[num_grants] = candidate;
grant = &grants[num_grants];
num_grants++;
grant->offset = htonl(new_grant);
priority = homa->max_sched_prio - (rank - 1);
extra_levels = homa->max_sched_prio + 1 - num_grantable_peers;
if (extra_levels >= 0)
priority -= extra_levels;
if (priority < 0)
priority = 0;
grant->priority = priority;
tt_record3("sending grant for id %llu, offset %d, priority %d",
candidate->id, new_grant, priority);
if (new_grant == candidate->msgin.total_length) {
BUG_ON(candidate->msgin.extra_incoming != 0);
candidate->msgin.extra_incoming =
candidate->msgin.bytes_remaining;
atomic_add(candidate->msgin.extra_incoming,
&homa->extra_incoming);
homa_remove_grantable_locked(homa, candidate);
}
if (num_grants == MAX_GRANTS)
break;
}
if (homa->grant_nonfifo_left <= 0) {
homa->grant_nonfifo_left += homa->grant_nonfifo;
if ((num_grantable_peers > homa->max_overcommit)
&& homa->grant_fifo_fraction)
homa_grant_fifo(homa);
}
homa_grantable_unlock(homa);
/* By sending grants without holding grantable_lock here, we reduce
* contention on that lock significantly. This only works because
* rpc->grants_in_progress keeps the RPC from being deleted out from
* under us.
*/
for (i = 0; i < num_grants; i++) {
/* Send any accumulated grants (ignore errors). */
BUG_ON(rpcs[i]->magic != HOMA_RPC_MAGIC);
homa_xmit_control(GRANT, &grants[i], sizeof(grants[i]),
rpcs[i]);
atomic_dec(&rpcs[i]->grants_in_progress);
}
INC_METRIC(grant_cycles, get_cycles() - start);
}
/**
* homa_grant_fifo() - This function is invoked occasionally to give
* a high-priority grant to the oldest incoming message. We do this in
* order to reduce the starvation that SRPT can cause for long messages.
* @homa: Overall data about the Homa protocol implementation. The
* grantable_lock must be held by the caller.
*/
void homa_grant_fifo(struct homa *homa)
{
struct homa_rpc *candidate, *oldest;
__u64 oldest_birth;
struct homa_peer *peer;
struct grant_header grant;
oldest = NULL;