details: https://hg.nginx.org/nginx/rev/e2d07e4ec636
branches:
changeset: 7992:e2d07e4ec636
user: Maxim Dounin <mdounin@mdounin.ru>
date: Thu Dec 30 01:08:46 2021 +0300
description:
Events: fixed balancing between workers with EPOLLEXCLUSIVE.

Linux with EPOLLEXCLUSIVE usually notifies only the process which was first
to add the listening socket to the epoll instance. As a result most of the
connections are handled by the first worker process (ticket #2285). To fix
this, we re-add the socket periodically, so other workers will get a chance
to accept connections.

diffstat:

src/event/ngx_event.c | 5 +++
src/event/ngx_event.h | 1 +
src/event/ngx_event_accept.c | 58 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 64 insertions(+), 0 deletions(-)

diffs (122 lines):

diff -r 57581198e51e -r e2d07e4ec636 src/event/ngx_event.c
--- a/src/event/ngx_event.c Wed Dec 29 22:59:53 2021 +0300
+++ b/src/event/ngx_event.c Thu Dec 30 01:08:46 2021 +0300
@@ -55,6 +55,7 @@ ngx_uint_t ngx_accept_events;
ngx_uint_t ngx_accept_mutex_held;
ngx_msec_t ngx_accept_mutex_delay;
ngx_int_t ngx_accept_disabled;
+ngx_uint_t ngx_use_exclusive_accept;


#if (NGX_STAT_STUB)
@@ -644,6 +645,8 @@ ngx_event_process_init(ngx_cycle_t *cycl

#endif

+ ngx_use_exclusive_accept = 0;
+
ngx_queue_init(&ngx_posted_accept_events);
ngx_queue_init(&ngx_posted_next_events);
ngx_queue_init(&ngx_posted_events);
@@ -889,6 +892,8 @@ ngx_event_process_init(ngx_cycle_t *cycl
if ((ngx_event_flags & NGX_USE_EPOLL_EVENT)
&& ccf->worker_processes > 1)
{
+ ngx_use_exclusive_accept = 1;
+
if (ngx_add_event(rev, NGX_READ_EVENT, NGX_EXCLUSIVE_EVENT)
== NGX_ERROR)
{
diff -r 57581198e51e -r e2d07e4ec636 src/event/ngx_event.h
--- a/src/event/ngx_event.h Wed Dec 29 22:59:53 2021 +0300
+++ b/src/event/ngx_event.h Thu Dec 30 01:08:46 2021 +0300
@@ -462,6 +462,7 @@ extern ngx_uint_t ngx_accept
extern ngx_uint_t ngx_accept_mutex_held;
extern ngx_msec_t ngx_accept_mutex_delay;
extern ngx_int_t ngx_accept_disabled;
+extern ngx_uint_t ngx_use_exclusive_accept;


#if (NGX_STAT_STUB)
diff -r 57581198e51e -r e2d07e4ec636 src/event/ngx_event_accept.c
--- a/src/event/ngx_event_accept.c Wed Dec 29 22:59:53 2021 +0300
+++ b/src/event/ngx_event_accept.c Thu Dec 30 01:08:46 2021 +0300
@@ -11,6 +11,9 @@


static ngx_int_t ngx_disable_accept_events(ngx_cycle_t *cycle, ngx_uint_t all);
+#if (NGX_HAVE_EPOLLEXCLUSIVE)
+static void ngx_reorder_accept_events(ngx_listening_t *ls);
+#endif
static void ngx_close_accepted_connection(ngx_connection_t *c);


@@ -314,6 +317,10 @@ ngx_event_accept(ngx_event_t *ev)
}

} while (ev->available);
+
+#if (NGX_HAVE_EPOLLEXCLUSIVE)
+ ngx_reorder_accept_events(ls);
+#endif
}


@@ -420,6 +427,57 @@ ngx_disable_accept_events(ngx_cycle_t *c
}


+#if (NGX_HAVE_EPOLLEXCLUSIVE)
+
+static void
+ngx_reorder_accept_events(ngx_listening_t *ls)
+{
+ ngx_connection_t *c;
+
+ /*
+ * Linux with EPOLLEXCLUSIVE usually notifies only the process which
+ * was first to add the listening socket to the epoll instance. As
+ * a result most of the connections are handled by the first worker
+ * process. To fix this, we re-add the socket periodically, so other
+ * workers will get a chance to accept connections.
+ */
+
+ if (!ngx_use_exclusive_accept) {
+ return;
+ }
+
+#if (NGX_HAVE_REUSEPORT)
+
+ if (ls->reuseport) {
+ return;
+ }
+
+#endif
+
+ c = ls->connection;
+
+ if (c->requests++ % 16 != 0
+ && ngx_accept_disabled <= 0)
+ {
+ return;
+ }
+
+ if (ngx_del_event(c->read, NGX_READ_EVENT, NGX_DISABLE_EVENT)
+ == NGX_ERROR)
+ {
+ return;
+ }
+
+ if (ngx_add_event(c->read, NGX_READ_EVENT, NGX_EXCLUSIVE_EVENT)
+ == NGX_ERROR)
+ {
+ return;
+ }
+}
+
+#endif
+
+
static void
ngx_close_accepted_connection(ngx_connection_t *c)
{
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