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Events: support for EPOLLEXCLUSIVE.

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This flag appeared in Linux 4.5 and is useful for avoiding thundering herd
problem.

The current Linux kernel implementation walks the list of exclusive waiters,
and queues an event to each epfd, until it finds the first waiter that has
threads blocked on it via epoll_wait().
This commit is contained in:
Valentin Bartenev 2016-07-15 15:18:57 +03:00
parent b60534e0d8
commit 5c2dd3913a
5 changed files with 60 additions and 5 deletions
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1
auto/modules
View File

@ -43,6 +43,7 @@ fi
if [ $NGX_TEST_BUILD_EPOLL = YES ]; then
have=NGX_HAVE_EPOLL . auto/have
have=NGX_HAVE_EPOLLRDHUP . auto/have
have=NGX_HAVE_EPOLLEXCLUSIVE . auto/have
have=NGX_HAVE_EVENTFD . auto/have
have=NGX_TEST_BUILD_EPOLL . auto/have
EVENT_MODULES="$EVENT_MODULES $EPOLL_MODULE"

16
auto/os/linux
View File

@ -70,6 +70,22 @@ if [ $ngx_found = yes ]; then
ee.data.ptr = NULL;
epoll_ctl(efd, EPOLL_CTL_ADD, fd, &ee)"
. auto/feature
# EPOLLEXCLUSIVE appeared in Linux 4.5, glibc 2.24
ngx_feature="EPOLLEXCLUSIVE"
ngx_feature_name="NGX_HAVE_EPOLLEXCLUSIVE"
ngx_feature_run=no
ngx_feature_incs="#include <sys/epoll.h>"
ngx_feature_path=
ngx_feature_libs=
ngx_feature_test="int efd = 0, fd = 0;
struct epoll_event ee;
ee.events = EPOLLIN|EPOLLEXCLUSIVE;
ee.data.ptr = NULL;
epoll_ctl(efd, EPOLL_CTL_ADD, fd, &ee)"
. auto/feature
fi

7
src/event/modules/ngx_epoll_module.c
View File

@ -27,6 +27,7 @@
#define EPOLLRDHUP 0x2000
#define EPOLLEXCLUSIVE 0x10000000
#define EPOLLONESHOT 0x40000000
#define EPOLLET 0x80000000
@ -610,6 +611,12 @@ ngx_epoll_add_event(ngx_event_t *ev, ngx_int_t event, ngx_uint_t flags)
op = EPOLL_CTL_ADD;
}
#if (NGX_HAVE_EPOLLEXCLUSIVE && NGX_HAVE_EPOLLRDHUP)
if (flags & NGX_EXCLUSIVE_EVENT) {
events &= ~EPOLLRDHUP;
}
#endif
ee.events = events | (uint32_t) flags;
ee.data.ptr = (void *) ((uintptr_t) c | ev->instance);

33
src/event/ngx_event.c
View File

@ -822,15 +822,38 @@ ngx_event_process_init(ngx_cycle_t *cycle)
rev->handler = (c->type == SOCK_STREAM) ? ngx_event_accept
: ngx_event_recvmsg;
if (ngx_use_accept_mutex
#if (NGX_HAVE_REUSEPORT)
&& !ls[i].reuseport
#endif
)
{
if (ls[i].reuseport) {
if (ngx_add_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
return NGX_ERROR;
}
continue;
}
#endif
if (ngx_use_accept_mutex) {
continue;
}
#if (NGX_HAVE_EPOLLEXCLUSIVE)
if ((ngx_event_flags & NGX_USE_EPOLL_EVENT)
&& ccf->worker_processes > 1)
{
if (ngx_add_event(rev, NGX_READ_EVENT, NGX_EXCLUSIVE_EVENT)
== NGX_ERROR)
{
return NGX_ERROR;
}
continue;
}
#endif
if (ngx_add_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
return NGX_ERROR;
}

8
src/event/ngx_event.h
View File

@ -367,6 +367,9 @@ extern ngx_uint_t ngx_use_epoll_rdhup;
#define NGX_ONESHOT_EVENT EPOLLONESHOT
#endif
#if (NGX_HAVE_EPOLLEXCLUSIVE)
#define NGX_EXCLUSIVE_EVENT EPOLLEXCLUSIVE
#endif
#elif (NGX_HAVE_POLL)
@ -395,6 +398,11 @@ extern ngx_uint_t ngx_use_epoll_rdhup;
#endif
#if (NGX_TEST_BUILD_EPOLL)
#define NGX_EXCLUSIVE_EVENT 0
#endif
#ifndef NGX_CLEAR_EVENT
#define NGX_CLEAR_EVENT 0 /* dummy declaration */
#endif