From 4938d7e0233a455f04507bac81d0886c71529537 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 16 Jun 2009 15:33:36 -0700 Subject: poll: avoid extra wakeups in select/poll After introduction of keyed wakeups Davide Libenzi did on epoll, we are able to avoid spurious wakeups in poll()/select() code too. For example, typical use of poll()/select() is to wait for incoming network frames on many sockets. But TX completion for UDP/TCP frames call sock_wfree() which in turn schedules thread. When scheduled, thread does a full scan of all polled fds and can sleep again, because nothing is really available. If number of fds is large, this cause significant load. This patch makes select()/poll() aware of keyed wakeups and useless wakeups are avoided. This reduces number of context switches by about 50% on some setups, and work performed by sofirq handlers. Signed-off-by: Eric Dumazet Acked-by: David S. Miller Acked-by: Andi Kleen Acked-by: Ingo Molnar Acked-by: Davide Libenzi Cc: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/poll.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux') diff --git a/include/linux/poll.h b/include/linux/poll.h index 8c24ef8d9976..fa287f25138d 100644 --- a/include/linux/poll.h +++ b/include/linux/poll.h @@ -32,6 +32,7 @@ typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_ typedef struct poll_table_struct { poll_queue_proc qproc; + unsigned long key; } poll_table; static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p) @@ -43,10 +44,12 @@ static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_addres static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc) { pt->qproc = qproc; + pt->key = ~0UL; /* all events enabled */ } struct poll_table_entry { struct file *filp; + unsigned long key; wait_queue_t wait; wait_queue_head_t *wait_address; }; -- cgit v1.2.3-59-g8ed1b