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Merge pull request #487 from h2o/kazuho/optimize-ack-ack
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opportunistically reduce the number of ack ranges added to sentmap
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@kazuho
kazuho authored Sep 1, 2021
2 parents 5b933b2 + 2c11d69 commit 17cc2f9
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Showing 2 changed files with 113 additions and 36 deletions.
25 changes: 24 additions & 1 deletion include/quicly/sentmap.h
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Original file line number Diff line number Diff line change
Expand Up @@ -91,12 +91,35 @@ typedef enum en_quicly_sentmap_event_t {
*/
typedef int (*quicly_sent_acked_cb)(quicly_sentmap_t *map, const quicly_sent_packet_t *packet, int acked, quicly_sent_t *data);

struct st_quicly_sent_ack_additional_t {
uint8_t gap;
uint8_t length;
};

/**
* Describes what is inside a packet or frame being sent. Within the sentmap, each packet-level entry (identified by .acked ==
* quicly_sentmap__type_packet) is followed by a number of frame-level entries. Size of `quicly_sent_t` is kept as 256 bits (64-bit
* * 4).
*/
struct st_quicly_sent_t {
quicly_sent_acked_cb acked;
union {
quicly_sent_packet_t packet;
/**
* ACK frame. Represents up to 8 ack ranges. If not full, `additional` list is terminated by .gap = 0.
*/
struct {
quicly_range_t range;
uint64_t start;
union {
struct {
uint64_t start_length;
struct st_quicly_sent_ack_additional_t additional[4];
} ranges64;
struct {
uint8_t start_length;
struct st_quicly_sent_ack_additional_t additional[7];
} ranges8;
};
} ack;
struct {
quicly_stream_id_t stream_id;
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124 changes: 89 additions & 35 deletions lib/quicly.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2530,45 +2530,72 @@ static int decrypt_packet(ptls_cipher_context_t *header_protection,
return 0;
}

static int on_ack_ack(quicly_sentmap_t *map, const quicly_sent_packet_t *packet, int acked, quicly_sent_t *sent)
static int do_on_ack_ack(quicly_conn_t *conn, const quicly_sent_packet_t *packet, uint64_t start, uint64_t start_length,
struct st_quicly_sent_ack_additional_t *additional, size_t additional_capacity)
{
quicly_conn_t *conn = (quicly_conn_t *)((char *)map - offsetof(quicly_conn_t, egress.loss.sentmap));

/* TODO log */
/* find the pn space */
struct st_quicly_pn_space_t *space;
switch (packet->ack_epoch) {
case QUICLY_EPOCH_INITIAL:
space = &conn->initial->super;
break;
case QUICLY_EPOCH_HANDSHAKE:
space = &conn->handshake->super;
break;
case QUICLY_EPOCH_1RTT:
space = &conn->application->super;
break;
default:
assert(!"FIXME");
return QUICLY_TRANSPORT_ERROR_INTERNAL;
}

if (acked) {
/* find the pn space */
struct st_quicly_pn_space_t *space;
switch (packet->ack_epoch) {
case QUICLY_EPOCH_INITIAL:
space = &conn->initial->super;
break;
case QUICLY_EPOCH_HANDSHAKE:
space = &conn->handshake->super;
break;
case QUICLY_EPOCH_1RTT:
space = &conn->application->super;
break;
default:
assert(!"FIXME");
return QUICLY_TRANSPORT_ERROR_INTERNAL;
}
/* subtract given ACK range, then make adjustments */
int ret;
if ((ret = quicly_ranges_subtract(&space->ack_queue, sent->data.ack.range.start, sent->data.ack.range.end)) != 0)
/* subtract given ACK ranges */
int ret;
uint64_t end = start + start_length;
if ((ret = quicly_ranges_subtract(&space->ack_queue, start, end)) != 0)
return ret;
for (size_t i = 0; i < additional_capacity && additional[i].gap != 0; ++i) {
start = end + additional[i].gap;
end = start + additional[i].length;
if ((ret = quicly_ranges_subtract(&space->ack_queue, start, end)) != 0)
return ret;
if (space->ack_queue.num_ranges == 0) {
space->largest_pn_received_at = INT64_MAX;
space->unacked_count = 0;
} else if (space->ack_queue.num_ranges > QUICLY_MAX_ACK_BLOCKS) {
quicly_ranges_drop_by_range_indices(&space->ack_queue, space->ack_queue.num_ranges - QUICLY_MAX_ACK_BLOCKS,
space->ack_queue.num_ranges);
}
}

/* make adjustments */
if (space->ack_queue.num_ranges == 0) {
space->largest_pn_received_at = INT64_MAX;
space->unacked_count = 0;
} else if (space->ack_queue.num_ranges > QUICLY_MAX_ACK_BLOCKS) {
quicly_ranges_drop_by_range_indices(&space->ack_queue, space->ack_queue.num_ranges - QUICLY_MAX_ACK_BLOCKS,
space->ack_queue.num_ranges);
}

return 0;
}

static int on_ack_ack_ranges64(quicly_sentmap_t *map, const quicly_sent_packet_t *packet, int acked, quicly_sent_t *sent)
{
quicly_conn_t *conn = (quicly_conn_t *)((char *)map - offsetof(quicly_conn_t, egress.loss.sentmap));

/* TODO log */

return acked ? do_on_ack_ack(conn, packet, sent->data.ack.start, sent->data.ack.ranges64.start_length,
sent->data.ack.ranges64.additional, PTLS_ELEMENTSOF(sent->data.ack.ranges64.additional))
: 0;
}

static int on_ack_ack_ranges8(quicly_sentmap_t *map, const quicly_sent_packet_t *packet, int acked, quicly_sent_t *sent)
{
quicly_conn_t *conn = (quicly_conn_t *)((char *)map - offsetof(quicly_conn_t, egress.loss.sentmap));

/* TODO log */

return acked ? do_on_ack_ack(conn, packet, sent->data.ack.start, sent->data.ack.ranges8.start_length,
sent->data.ack.ranges8.additional, PTLS_ELEMENTSOF(sent->data.ack.ranges8.additional))
: 0;
}

static int on_ack_stream_ack_one(quicly_conn_t *conn, quicly_stream_id_t stream_id, quicly_sendstate_sent_t *sent)
{
quicly_stream_t *stream;
Expand Down Expand Up @@ -3313,12 +3340,39 @@ static int send_ack(quicly_conn_t *conn, struct st_quicly_pn_space_t *space, qui
s->dst = dst;

{ /* save what's inflight */
size_t i;
for (i = 0; i != space->ack_queue.num_ranges; ++i) {
size_t range_index = 0;
while (range_index < space->ack_queue.num_ranges) {
quicly_sent_t *sent;
if ((sent = quicly_sentmap_allocate(&conn->egress.loss.sentmap, on_ack_ack)) == NULL)
struct st_quicly_sent_ack_additional_t *additional, *additional_end;
/* allocate */
if ((sent = quicly_sentmap_allocate(&conn->egress.loss.sentmap, on_ack_ack_ranges8)) == NULL)
return PTLS_ERROR_NO_MEMORY;
sent->data.ack.range = space->ack_queue.ranges[i];
/* store the first range, as well as preparing references to the additional slots */
sent->data.ack.start = space->ack_queue.ranges[range_index].start;
uint64_t length = space->ack_queue.ranges[range_index].end - space->ack_queue.ranges[range_index].start;
if (length <= UINT8_MAX) {
sent->data.ack.ranges8.start_length = length;
additional = sent->data.ack.ranges8.additional;
additional_end = additional + PTLS_ELEMENTSOF(sent->data.ack.ranges8.additional);
} else {
sent->acked = on_ack_ack_ranges64;
sent->data.ack.ranges64.start_length = length;
additional = sent->data.ack.ranges64.additional;
additional_end = additional + PTLS_ELEMENTSOF(sent->data.ack.ranges64.additional);
}
/* store additional ranges, if possible */
for (++range_index; range_index < space->ack_queue.num_ranges && additional < additional_end;
++range_index, ++additional) {
uint64_t gap = space->ack_queue.ranges[range_index].start - space->ack_queue.ranges[range_index - 1].end;
uint64_t length = space->ack_queue.ranges[range_index].end - space->ack_queue.ranges[range_index].start;
if (gap > UINT8_MAX || length > UINT8_MAX)
break;
additional->gap = gap;
additional->length = length;
}
/* additional list is zero-terminated, if not full */
if (additional < additional_end)
additional->gap = 0;
}
}

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