From d251efe740fd87d60231a6b380aaf6ff2faedd5b Mon Sep 17 00:00:00 2001
From: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Date: Wed, 17 Apr 2019 15:58:54 +0300
Subject: [PATCH] swim: do not rebuild packet meta multiple times
Before the patch there were 2 cases when an unchanged packet was
rebuilt partially on each send:
- cached round message's meta section was rebuilt on each
EV_WRITE event in swim_scheduler_on_output() function;
- broadcast message's meta section was rebuilt too even though
its content does not depend on a broadcast interface.
The third case appears with indirect pings patch which aggravates
meta building business by routing and packet forwarding. When a
packet needs to be forwarded farther, its meta is built in a
special manner preserving the route before EV_WRITE appears, and
on_output should not touch that meta.
This patch adds a check preventing unnecessary meta rebuilds.
Besides, the check and the meta building code are moved into a
dedicated function out of swim_scheduler_on_output() - it allows
to completely split logic of packing a message and sending it.
Separated logic helps a lot when indirect pings are introduced.
Part of #3234
---
src/lib/swim/swim_io.c | 29 ++++++++++++++++++++++++++---
1 file changed, 26 insertions(+), 3 deletions(-)
diff --git a/src/lib/swim/swim_io.c b/src/lib/swim/swim_io.c
index 03d79ae3e1..7d6addf02f 100644
--- a/src/lib/swim/swim_io.c
+++ b/src/lib/swim/swim_io.c
@@ -57,6 +57,31 @@ swim_packet_create(struct swim_packet *packet)
swim_packet_alloc_meta(packet, sizeof(struct swim_meta_header_bin));
}
+/** Fill metadata prefix of a packet. */
+static inline void
+swim_packet_build_meta(struct swim_packet *packet,
+ const struct sockaddr_in *src)
+{
+ char *meta = packet->meta;
+ char *end = packet->body;
+ /*
+ * Meta has already been built. It happens when the same
+ * task is resent multiple times.
+ */
+ if (meta == end)
+ return;
+ struct swim_meta_header_bin header;
+ swim_meta_header_bin_create(&header, src);
+ assert(meta + sizeof(header) == end);
+ memcpy(meta, &header, sizeof(header));
+ /*
+ * Once meta is built, it is consumed by the body. Used
+ * not to rebuild the meta again if the task will be
+ * scheduled again without changes in data.
+ */
+ packet->body = packet->meta;
+}
+
void
swim_task_create(struct swim_task *task, swim_task_f complete,
swim_task_f cancel, const char *desc)
@@ -298,9 +323,7 @@ swim_scheduler_on_output(struct ev_loop *loop, struct ev_io *io, int events)
say_verbose("SWIM %d: send %s to %s", swim_scheduler_fd(scheduler),
task->desc, sio_strfaddr((struct sockaddr *) &task->dst,
sizeof(task->dst)));
- struct swim_meta_header_bin header;
- swim_meta_header_bin_create(&header, &scheduler->transport.addr);
- memcpy(task->packet.meta, &header, sizeof(header));
+ swim_packet_build_meta(&task->packet, &scheduler->transport.addr);
int rc = swim_transport_send(&scheduler->transport, task->packet.buf,
task->packet.pos - task->packet.buf,
(const struct sockaddr *) &task->dst,
--
GitLab