linux-stable/include/linux/poll.h
Eric Dumazet 4938d7e023 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>
2009-06-16 19:47:48 -07:00

139 lines
3.5 KiB
C

#ifndef _LINUX_POLL_H
#define _LINUX_POLL_H
#include <asm/poll.h>
#ifdef __KERNEL__
#include <linux/compiler.h>
#include <linux/wait.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <asm/uaccess.h>
/* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
additional memory. */
#define MAX_STACK_ALLOC 832
#define FRONTEND_STACK_ALLOC 256
#define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC
#define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC
#define WQUEUES_STACK_ALLOC (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
#define N_INLINE_POLL_ENTRIES (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
#define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
struct poll_table_struct;
/*
* structures and helpers for f_op->poll implementations
*/
typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
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)
{
if (p && wait_address)
p->qproc(filp, wait_address, p);
}
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;
};
/*
* Structures and helpers for sys_poll/sys_poll
*/
struct poll_wqueues {
poll_table pt;
struct poll_table_page *table;
struct task_struct *polling_task;
int triggered;
int error;
int inline_index;
struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
};
extern void poll_initwait(struct poll_wqueues *pwq);
extern void poll_freewait(struct poll_wqueues *pwq);
extern int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
ktime_t *expires, unsigned long slack);
static inline int poll_schedule(struct poll_wqueues *pwq, int state)
{
return poll_schedule_timeout(pwq, state, NULL, 0);
}
/*
* Scaleable version of the fd_set.
*/
typedef struct {
unsigned long *in, *out, *ex;
unsigned long *res_in, *res_out, *res_ex;
} fd_set_bits;
/*
* How many longwords for "nr" bits?
*/
#define FDS_BITPERLONG (8*sizeof(long))
#define FDS_LONGS(nr) (((nr)+FDS_BITPERLONG-1)/FDS_BITPERLONG)
#define FDS_BYTES(nr) (FDS_LONGS(nr)*sizeof(long))
/*
* We do a VERIFY_WRITE here even though we are only reading this time:
* we'll write to it eventually..
*
* Use "unsigned long" accesses to let user-mode fd_set's be long-aligned.
*/
static inline
int get_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
{
nr = FDS_BYTES(nr);
if (ufdset)
return copy_from_user(fdset, ufdset, nr) ? -EFAULT : 0;
memset(fdset, 0, nr);
return 0;
}
static inline unsigned long __must_check
set_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
{
if (ufdset)
return __copy_to_user(ufdset, fdset, FDS_BYTES(nr));
return 0;
}
static inline
void zero_fd_set(unsigned long nr, unsigned long *fdset)
{
memset(fdset, 0, FDS_BYTES(nr));
}
#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
extern int do_select(int n, fd_set_bits *fds, struct timespec *end_time);
extern int do_sys_poll(struct pollfd __user * ufds, unsigned int nfds,
struct timespec *end_time);
extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
fd_set __user *exp, struct timespec *end_time);
extern int poll_select_set_timeout(struct timespec *to, long sec, long nsec);
#endif /* KERNEL */
#endif /* _LINUX_POLL_H */