Messages in this thread Patch in this message | | | From | Hagen Paul Pfeifer <> | Subject | [PATCH Resend] epoll: add EPOLLEXCLUSIVE support | Date | Wed, 28 Mar 2012 15:57:40 +0200 |
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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 <hagen@jauu.net> --- Dave rejected the patch and said not network specific. Because there is no epoll maintainer this time directly.
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 629e9ed..16d787f 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 @@ -969,7 +969,10 @@ 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) -- 1.7.9.1
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