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Events: fixed balancing between workers with EPOLLEXCLUSIVE.

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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.
This commit is contained in:
Maxim Dounin 2021-12-30 01:08:46 +03:00
parent 7d591be08f
commit d29c0a2728
3 changed files with 64 additions and 0 deletions
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5
src/event/ngx_event.c
View file

@ -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 *cycle)
#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 *cycle)
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)
{

1
src/event/ngx_event.h
View file

@ -462,6 +462,7 @@ extern ngx_uint_t ngx_accept_events;
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)

58
src/event/ngx_event_accept.c
View file

@ -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 *cycle, ngx_uint_t all)
}
#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)
{