[PATCH net-next] epoll: add EPOLLEXCLUSIVE support
From: Hagen Paul Pfeifer <hidden>
Date: 2012-02-14 20:48:16
Also in:
lkml
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
High performance server sometimes create one listening socket (e.g. port 80), create a epoll file descriptor and add the socket. Afterwards create SC_NPROCESSORS_ONLN threads and wait for events. This often result in a thundering herd problem because all CPUs are scheduled. This patch add an additional flag to epoll_ctl(2) called EPOLLEXCLUSIVE. If a descriptor is added with this flag only one CPU is scheduled in. Signed-off-by: Hagen Paul Pfeifer <redacted> Reported-by: Li Yu <redacted> Cc: Davide Libenzi <redacted> Cc: Eric Dumazet <redacted> --- fs/eventpoll.c | 7 +++++-- include/linux/eventpoll.h | 3 +++ 2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index aabdfc3..bb442b1 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c@@ -88,7 +88,7 @@ */ /* Epoll private bits inside the event mask */ -#define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET) +#define EP_PRIVATE_BITS (EPOLLONESHOT | EPOLLET | EPOLLEXCLUSIVE) /* Maximum number of nesting allowed inside epoll sets */ #define EP_MAX_NESTS 4
@@ -913,7 +913,10 @@ static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); pwq->whead = whead; pwq->base = epi; - add_wait_queue(whead, &pwq->wait); + if (unlikely(epi->event.events & EPOLLEXCLUSIVE)) + add_wait_queue_exclusive(whead, &pwq->wait); + else + add_wait_queue(whead, &pwq->wait); list_add_tail(&pwq->llink, &epi->pwqlist); epi->nwait++; } else {
diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
index 657ab55..d334389 100644
--- a/include/linux/eventpoll.h
+++ b/include/linux/eventpoll.h@@ -26,6 +26,9 @@ #define EPOLL_CTL_DEL 2 #define EPOLL_CTL_MOD 3 +/* Set Exclusive wake up behaviour for the target file descriptor */ +#define EPOLLEXCLUSIVE (1 << 29) + /* Set the One Shot behaviour for the target file descriptor */ #define EPOLLONESHOT (1 << 30)
--
1.7.9