As it says in rfc8260#section-3.5 about the fair capacity scheduler:
A fair capacity distribution between the streams is used. This
scheduler considers the lengths of the messages of each stream and
schedules them in a specific way to maintain an equal capacity for
all streams. The details are implementation dependent. interleaving
user messages allows for a better realization of the fair capacity
usage.
This patch adds Fair Capacity Scheduler based on the foundations added
by commit 5bbbbe32a431 ("sctp: introduce stream scheduler foundations"):
A fc_list and a fc_length are added into struct sctp_stream_out_ext and
a fc_list is added into struct sctp_stream. In .enqueue, when there are
chunks enqueued into a stream, this stream will be linked into stream->
fc_list by its fc_list ordered by its fc_length. In .dequeue, it always
picks up the 1st skb from stream->fc_list. In .dequeue_done, fc_length
is increased by chunk's len and update its location in stream->fc_list
according to the its new fc_length.
Note that when the new fc_length overflows in .dequeue_done, instead of
resetting all fc_lengths to 0, we only reduced them by U32_MAX / 4 to
avoid a moment of imbalance in the scheduling, as Marcelo suggested.
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
---
include/net/sctp/stream_sched.h | 1 +
include/net/sctp/structs.h | 7 ++
include/uapi/linux/sctp.h | 3 +-
net/sctp/Makefile | 3 +-
net/sctp/stream_sched.c | 1 +
net/sctp/stream_sched_fc.c | 183 ++++++++++++++++++++++++++++++++
6 files changed, 196 insertions(+), 2 deletions(-)
create mode 100644 net/sctp/stream_sched_fc.c
diff --git a/include/net/sctp/stream_sched.h b/include/net/sctp/stream_sched.h
index fa00dc20a0d7..913170710adb 100644
--- a/include/net/sctp/stream_sched.h
+++ b/include/net/sctp/stream_sched.h
@@ -58,5 +58,6 @@ void sctp_sched_ops_register(enum sctp_sched_type sched,
struct sctp_sched_ops *sched_ops);
void sctp_sched_ops_prio_init(void);
void sctp_sched_ops_rr_init(void);
+void sctp_sched_ops_fc_init(void);
#endif /* __sctp_stream_sched_h__ */
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index e1f6e7fc2b11..2f1c9f50b352 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1429,6 +1429,10 @@ struct sctp_stream_out_ext {
struct {
struct list_head rr_list;
};
+ struct {
+ struct list_head fc_list;
+ __u32 fc_length;
+ };
};
};
@@ -1475,6 +1479,9 @@ struct sctp_stream {
/* The next stream in line */
struct sctp_stream_out_ext *rr_next;
};
+ struct {
+ struct list_head fc_list;
+ };
};
struct sctp_stream_interleave *si;
};
diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
index ed7d4ecbf53d..6814c5a1c4bc 100644
--- a/include/uapi/linux/sctp.h
+++ b/include/uapi/linux/sctp.h
@@ -1211,7 +1211,8 @@ enum sctp_sched_type {
SCTP_SS_DEFAULT = SCTP_SS_FCFS,
SCTP_SS_PRIO,
SCTP_SS_RR,
- SCTP_SS_MAX = SCTP_SS_RR
+ SCTP_SS_FC,
+ SCTP_SS_MAX = SCTP_SS_FC
};
/* Probe Interval socket option */
diff --git a/net/sctp/Makefile b/net/sctp/Makefile
index e845e4588535..0448398408d8 100644
--- a/net/sctp/Makefile
+++ b/net/sctp/Makefile
@@ -13,7 +13,8 @@ sctp-y := sm_statetable.o sm_statefuns.o sm_sideeffect.o \
tsnmap.o bind_addr.o socket.o primitive.o \
output.o input.o debug.o stream.o auth.o \
offload.o stream_sched.o stream_sched_prio.o \
- stream_sched_rr.o stream_interleave.o
+ stream_sched_rr.o stream_sched_fc.o \
+ stream_interleave.o
sctp_diag-y := diag.o
diff --git a/net/sctp/stream_sched.c b/net/sctp/stream_sched.c
index 330067002deb..1ebd14ef8daa 100644
--- a/net/sctp/stream_sched.c
+++ b/net/sctp/stream_sched.c
@@ -124,6 +124,7 @@ void sctp_sched_ops_init(void)
sctp_sched_ops_fcfs_init();
sctp_sched_ops_prio_init();
sctp_sched_ops_rr_init();
+ sctp_sched_ops_fc_init();
}
static void sctp_sched_free_sched(struct sctp_stream *stream)
diff --git a/net/sctp/stream_sched_fc.c b/net/sctp/stream_sched_fc.c
new file mode 100644
index 000000000000..b336c2f5486b
--- /dev/null
+++ b/net/sctp/stream_sched_fc.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* SCTP kernel implementation
+ * (C) Copyright Red Hat Inc. 2022
+ *
+ * This file is part of the SCTP kernel implementation
+ *
+ * These functions manipulate sctp stream queue/scheduling.
+ *
+ * Please send any bug reports or fixes you make to the
+ * email addresched(es):
+ * lksctp developers <linux-sctp@xxxxxxxxxxxxxxx>
+ *
+ * Written or modified by:
+ * Xin Long <lucien.xin@xxxxxxxxx>
+ */
+
+#include <linux/list.h>
+#include <net/sctp/sctp.h>
+#include <net/sctp/sm.h>
+#include <net/sctp/stream_sched.h>
+
+/* Fair Capacity handling
+ * RFC 8260 section 3.5
+ */
+static void sctp_sched_fc_unsched_all(struct sctp_stream *stream);
+
+static int sctp_sched_fc_set(struct sctp_stream *stream, __u16 sid,
+ __u16 weight, gfp_t gfp)
+{
+ return 0;
+}
+
+static int sctp_sched_fc_get(struct sctp_stream *stream, __u16 sid,
+ __u16 *value)
+{
+ return 0;
+}
+
+static int sctp_sched_fc_init(struct sctp_stream *stream)
+{
+ INIT_LIST_HEAD(&stream->fc_list);
+
+ return 0;
+}
+
+static int sctp_sched_fc_init_sid(struct sctp_stream *stream, __u16 sid,
+ gfp_t gfp)
+{
+ struct sctp_stream_out_ext *soute = SCTP_SO(stream, sid)->ext;
+
+ INIT_LIST_HEAD(&soute->fc_list);
+ soute->fc_length = 0;
+
+ return 0;
+}
+
+static void sctp_sched_fc_free_sid(struct sctp_stream *stream, __u16 sid)
+{
+}
+
+static void sctp_sched_fc_sched(struct sctp_stream *stream,
+ struct sctp_stream_out_ext *soute)
+{
+ struct sctp_stream_out_ext *pos;
+
+ if (!list_empty(&soute->fc_list))
+ return;
+
+ list_for_each_entry(pos, &stream->fc_list, fc_list)
+ if (pos->fc_length >= soute->fc_length)
+ break;
+ list_add_tail(&soute->fc_list, &pos->fc_list);
+}
+
+static void sctp_sched_fc_enqueue(struct sctp_outq *q,
+ struct sctp_datamsg *msg)
+{
+ struct sctp_stream *stream;
+ struct sctp_chunk *ch;
+ __u16 sid;
+
+ ch = list_first_entry(&msg->chunks, struct sctp_chunk, frag_list);
+ sid = sctp_chunk_stream_no(ch);
+ stream = &q->asoc->stream;
+ sctp_sched_fc_sched(stream, SCTP_SO(stream, sid)->ext);
+}
+
+static struct sctp_chunk *sctp_sched_fc_dequeue(struct sctp_outq *q)
+{
+ struct sctp_stream *stream = &q->asoc->stream;
+ struct sctp_stream_out_ext *soute;
+ struct sctp_chunk *ch;
+
+ /* Bail out quickly if queue is empty */
+ if (list_empty(&q->out_chunk_list))
+ return NULL;
+
+ /* Find which chunk is next */
+ if (stream->out_curr)
+ soute = stream->out_curr->ext;
+ else
+ soute = list_entry(stream->fc_list.next, struct sctp_stream_out_ext, fc_list);
+ ch = list_entry(soute->outq.next, struct sctp_chunk, stream_list);
+
+ sctp_sched_dequeue_common(q, ch);
+ return ch;
+}
+
+static void sctp_sched_fc_dequeue_done(struct sctp_outq *q,
+ struct sctp_chunk *ch)
+{
+ struct sctp_stream *stream = &q->asoc->stream;
+ struct sctp_stream_out_ext *soute, *pos;
+ __u16 sid, i;
+
+ sid = sctp_chunk_stream_no(ch);
+ soute = SCTP_SO(stream, sid)->ext;
+ /* reduce all fc_lengths by U32_MAX / 4 if the current fc_length overflows. */
+ if (soute->fc_length > U32_MAX - ch->skb->len) {
+ for (i = 0; i < stream->outcnt; i++) {
+ pos = SCTP_SO(stream, i)->ext;
+ if (!pos)
+ continue;
+ if (pos->fc_length <= (U32_MAX >> 2)) {
+ pos->fc_length = 0;
+ continue;
+ }
+ pos->fc_length -= (U32_MAX >> 2);
+ }
+ }
+ soute->fc_length += ch->skb->len;
+
+ if (list_empty(&soute->outq)) {
+ list_del_init(&soute->fc_list);
+ return;
+ }
+
+ pos = soute;
+ list_for_each_entry_continue(pos, &stream->fc_list, fc_list)
+ if (pos->fc_length >= soute->fc_length)
+ break;
+ list_move_tail(&soute->fc_list, &pos->fc_list);
+}
+
+static void sctp_sched_fc_sched_all(struct sctp_stream *stream)
+{
+ struct sctp_association *asoc;
+ struct sctp_chunk *ch;
+
+ asoc = container_of(stream, struct sctp_association, stream);
+ list_for_each_entry(ch, &asoc->outqueue.out_chunk_list, list) {
+ __u16 sid = sctp_chunk_stream_no(ch);
+
+ if (SCTP_SO(stream, sid)->ext)
+ sctp_sched_fc_sched(stream, SCTP_SO(stream, sid)->ext);
+ }
+}
+
+static void sctp_sched_fc_unsched_all(struct sctp_stream *stream)
+{
+ struct sctp_stream_out_ext *soute, *tmp;
+
+ list_for_each_entry_safe(soute, tmp, &stream->fc_list, fc_list)
+ list_del_init(&soute->fc_list);
+}
+
+static struct sctp_sched_ops sctp_sched_fc = {
+ .set = sctp_sched_fc_set,
+ .get = sctp_sched_fc_get,
+ .init = sctp_sched_fc_init,
+ .init_sid = sctp_sched_fc_init_sid,
+ .free_sid = sctp_sched_fc_free_sid,
+ .enqueue = sctp_sched_fc_enqueue,
+ .dequeue = sctp_sched_fc_dequeue,
+ .dequeue_done = sctp_sched_fc_dequeue_done,
+ .sched_all = sctp_sched_fc_sched_all,
+ .unsched_all = sctp_sched_fc_unsched_all,
+};
+
+void sctp_sched_ops_fc_init(void)
+{
+ sctp_sched_ops_register(SCTP_SS_FC, &sctp_sched_fc);
+}
--
2.39.1
