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Improved EPOLLRDHUP handling.

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When it's known that the kernel supports EPOLLRDHUP, there is no need in
additional recv() call to get EOF or error when the flag is absent in the
event generated by the kernel.  A special runtime test is done at startup
to detect if EPOLLRDHUP is actually supported by the kernel because
epoll_ctl() silently ignores unknown flags.

With this knowledge it's now possible to drop the "ready" flag for partial
read.  Previously, the "ready" flag was kept until the recv() returned EOF
or error.  In particular, this change allows the lingering close heuristics
(which relies on the "ready" flag state) to actually work on Linux, and not
wait for more data in most cases.

The "available" flag is now used in the read event with the semantics similar
to the corresponding counter in kqueue.
This commit is contained in:
Valentin Bartenev 2016-05-13 17:19:23 +03:00
parent cbf6ca98bc
commit 12f4367189
6 changed files with 153 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

72
src/event/modules/ngx_epoll_module.c
View File

@ -123,6 +123,7 @@ static ngx_int_t ngx_epoll_process_events(ngx_cycle_t *cycle, ngx_msec_t timer,
static void ngx_epoll_eventfd_handler(ngx_event_t *ev);
#endif
static ngx_int_t ngx_epoll_module_init(ngx_cycle_t *cycle);
static void *ngx_epoll_create_conf(ngx_cycle_t *cycle);
static char *ngx_epoll_init_conf(ngx_cycle_t *cycle, void *conf);
@ -146,6 +147,10 @@ static ngx_connection_t ngx_eventfd_conn;
#endif
#if (NGX_HAVE_EPOLLRDHUP)
ngx_uint_t ngx_use_epoll_rdhup;
#endif
static ngx_str_t epoll_name = ngx_string("epoll");
static ngx_command_t ngx_epoll_commands[] = {
@ -197,7 +202,7 @@ ngx_module_t ngx_epoll_module = {
ngx_epoll_commands, /* module directives */
NGX_EVENT_MODULE, /* module type */
NULL, /* init master */
NULL, /* init module */
ngx_epoll_module_init, /* init module */
NULL, /* init process */
NULL, /* init thread */
NULL, /* exit thread */
@ -808,6 +813,8 @@ ngx_epoll_process_events(ngx_cycle_t *cycle, ngx_msec_t timer, ngx_uint_t flags)
if (revents & EPOLLRDHUP) {
rev->pending_eof = 1;
}
rev->available = 1;
#endif
rev->ready = 1;
@ -943,6 +950,69 @@ ngx_epoll_eventfd_handler(ngx_event_t *ev)
#endif
static ngx_int_t
ngx_epoll_module_init(ngx_cycle_t *cycle)
{
#if (NGX_HAVE_EPOLLRDHUP)
int epfd, s[2], events;
struct epoll_event ee;
epfd = epoll_create(1);
if (epfd == -1) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"epoll_create() failed");
return NGX_ERROR;
}
if (socketpair(AF_UNIX, SOCK_STREAM, 0, s) == -1) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"socketpair() failed");
return NGX_ERROR;
}
ee.events = EPOLLET|EPOLLIN|EPOLLRDHUP;
if (epoll_ctl(epfd, EPOLL_CTL_ADD, s[0], &ee) == -1) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"epoll_ctl() failed");
return NGX_ERROR;
}
if (close(s[1]) == -1) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"close() failed");
return NGX_ERROR;
}
events = epoll_wait(epfd, &ee, 1, 5000);
if (events == -1) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"epoll_wait() failed");
return NGX_ERROR;
}
(void) close(s[0]);
(void) close(epfd);
if (events) {
ngx_use_epoll_rdhup = ee.events & EPOLLRDHUP;
} else {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"epoll_wait() timedout");
}
ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0,
"testing the EPOLLRDHUP flag: %s",
ngx_use_epoll_rdhup ? "success" : "fail");
#endif
return NGX_OK;
}
static void *
ngx_epoll_create_conf(ngx_cycle_t *cycle)
{

7
src/event/ngx_event.h
View File

@ -96,6 +96,10 @@ struct ngx_event_s {
* write: available space in buffer when event is ready
* or lowat when event is set with NGX_LOWAT_EVENT flag
*
* epoll with EPOLLRDHUP:
* accept: 1 if accept many, 0 otherwise
* read: 1 if there can be data to read, 0 otherwise
*
* iocp: TODO
*
* otherwise:
@ -196,6 +200,9 @@ typedef struct {
extern ngx_event_actions_t ngx_event_actions;
#if (NGX_HAVE_EPOLLRDHUP)
extern ngx_uint_t ngx_use_epoll_rdhup;
#endif
/*

6
src/http/ngx_http_request.c
View File

@ -2752,9 +2752,13 @@ ngx_http_test_reading(ngx_http_request_t *r)
#if (NGX_HAVE_EPOLLRDHUP)
if ((ngx_event_flags & NGX_USE_EPOLL_EVENT) && rev->pending_eof) {
if ((ngx_event_flags & NGX_USE_EPOLL_EVENT) && ngx_use_epoll_rdhup) {
socklen_t len;
if (!rev->pending_eof) {
return;
}
rev->eof = 1;
c->error = 1;

6
src/http/ngx_http_upstream.c
View File

@ -1222,9 +1222,13 @@ ngx_http_upstream_check_broken_connection(ngx_http_request_t *r,
#if (NGX_HAVE_EPOLLRDHUP)
if ((ngx_event_flags & NGX_USE_EPOLL_EVENT) && ev->pending_eof) {
if ((ngx_event_flags & NGX_USE_EPOLL_EVENT) && ngx_use_epoll_rdhup) {
socklen_t len;
if (!ev->pending_eof) {
return;
}
ev->eof = 1;
c->error = 1;

32
src/os/unix/ngx_readv_chain.c
View File

@ -51,6 +51,20 @@ ngx_readv_chain(ngx_connection_t *c, ngx_chain_t *chain, off_t limit)
}
}
#endif
#if (NGX_HAVE_EPOLLRDHUP)
if (ngx_event_flags & NGX_USE_EPOLL_EVENT) {
ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
"readv: eof:%d, avail:%d",
rev->pending_eof, rev->available);
if (!rev->available && !rev->pending_eof) {
return NGX_AGAIN;
}
}
#endif
prev = NULL;
@ -149,6 +163,24 @@ ngx_readv_chain(ngx_connection_t *c, ngx_chain_t *chain, off_t limit)
return n;
}
#endif
#if (NGX_HAVE_EPOLLRDHUP)
if ((ngx_event_flags & NGX_USE_EPOLL_EVENT)
&& ngx_use_epoll_rdhup)
{
if (n < size) {
if (!rev->pending_eof) {
rev->ready = 0;
}
rev->available = 0;
}
return n;
}
#endif
if (n < size && !(ngx_event_flags & NGX_USE_GREEDY_EVENT)) {

33
src/os/unix/ngx_recv.c
View File

@ -48,6 +48,21 @@ ngx_unix_recv(ngx_connection_t *c, u_char *buf, size_t size)
}
}
#endif
#if (NGX_HAVE_EPOLLRDHUP)
if (ngx_event_flags & NGX_USE_EPOLL_EVENT) {
ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
"recv: eof:%d, avail:%d",
rev->pending_eof, rev->available);
if (!rev->available && !rev->pending_eof) {
rev->ready = 0;
return NGX_AGAIN;
}
}
#endif
do {
@ -99,6 +114,24 @@ ngx_unix_recv(ngx_connection_t *c, u_char *buf, size_t size)
return n;
}
#endif
#if (NGX_HAVE_EPOLLRDHUP)
if ((ngx_event_flags & NGX_USE_EPOLL_EVENT)
&& ngx_use_epoll_rdhup)
{
if ((size_t) n < size) {
if (!rev->pending_eof) {
rev->ready = 0;
}
rev->available = 0;
}
return n;
}
#endif
if ((size_t) n < size