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author | 2009-06-16 15:33:36 -0700 | |
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committer | 2009-06-16 19:47:48 -0700 | |
commit | 4938d7e0233a455f04507bac81d0886c71529537 (patch) | |
tree | 6e0c6f0e8623ef44270890519f08b98e9db8afee /include/linux/poll.h | |
parent | ntfs: use is_power_of_2() function for clarity. (diff) | |
download | linux-4938d7e0233a455f04507bac81d0886c71529537.tar.gz linux-4938d7e0233a455f04507bac81d0886c71529537.tar.bz2 linux-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.h | 3 |
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; }; |