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authorEric Dumazet <dada1@cosmosbay.com>2009-06-16 15:33:36 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:48 -0700
commit4938d7e0233a455f04507bac81d0886c71529537 (patch)
tree6e0c6f0e8623ef44270890519f08b98e9db8afee /include/linux/poll.h
parent02d5341ae53d32681241b27a40397475caef1c83 (diff)
downloadlwn-4938d7e0233a455f04507bac81d0886c71529537.tar.gz
lwn-4938d7e0233a455f04507bac81d0886c71529537.zip
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 <dada1@cosmosbay.com> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Andi Kleen <ak@linux.intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Davide Libenzi <davidel@xmailserver.org> Cc: Christoph Lameter <cl@linux-foundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/poll.h')
-rw-r--r--include/linux/poll.h3
1 files changed, 3 insertions, 0 deletions
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;
};