4938d7e023
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>
140 lines
3.5 KiB
C
140 lines
3.5 KiB
C
#ifndef _LINUX_POLL_H
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#define _LINUX_POLL_H
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#include <asm/poll.h>
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#ifdef __KERNEL__
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#include <linux/compiler.h>
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#include <linux/wait.h>
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#include <linux/string.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <asm/uaccess.h>
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/* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
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additional memory. */
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#define MAX_STACK_ALLOC 832
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#define FRONTEND_STACK_ALLOC 256
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#define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC
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#define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC
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#define WQUEUES_STACK_ALLOC (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
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#define N_INLINE_POLL_ENTRIES (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
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#define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
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struct poll_table_struct;
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/*
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* structures and helpers for f_op->poll implementations
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*/
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typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
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typedef struct poll_table_struct {
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poll_queue_proc qproc;
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unsigned long key;
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} poll_table;
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static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
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{
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if (p && wait_address)
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p->qproc(filp, wait_address, p);
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}
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static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
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{
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pt->qproc = qproc;
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pt->key = ~0UL; /* all events enabled */
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}
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struct poll_table_entry {
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struct file *filp;
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unsigned long key;
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wait_queue_t wait;
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wait_queue_head_t *wait_address;
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};
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/*
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* Structures and helpers for sys_poll/sys_poll
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*/
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struct poll_wqueues {
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poll_table pt;
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struct poll_table_page *table;
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struct task_struct *polling_task;
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int triggered;
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int error;
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int inline_index;
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struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
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};
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extern void poll_initwait(struct poll_wqueues *pwq);
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extern void poll_freewait(struct poll_wqueues *pwq);
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extern int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
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ktime_t *expires, unsigned long slack);
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static inline int poll_schedule(struct poll_wqueues *pwq, int state)
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{
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return poll_schedule_timeout(pwq, state, NULL, 0);
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}
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/*
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* Scaleable version of the fd_set.
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*/
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typedef struct {
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unsigned long *in, *out, *ex;
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unsigned long *res_in, *res_out, *res_ex;
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} fd_set_bits;
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/*
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* How many longwords for "nr" bits?
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*/
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#define FDS_BITPERLONG (8*sizeof(long))
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#define FDS_LONGS(nr) (((nr)+FDS_BITPERLONG-1)/FDS_BITPERLONG)
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#define FDS_BYTES(nr) (FDS_LONGS(nr)*sizeof(long))
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/*
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* We do a VERIFY_WRITE here even though we are only reading this time:
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* we'll write to it eventually..
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*
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* Use "unsigned long" accesses to let user-mode fd_set's be long-aligned.
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*/
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static inline
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int get_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
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{
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nr = FDS_BYTES(nr);
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if (ufdset)
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return copy_from_user(fdset, ufdset, nr) ? -EFAULT : 0;
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memset(fdset, 0, nr);
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return 0;
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}
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static inline unsigned long __must_check
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set_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
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{
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if (ufdset)
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return __copy_to_user(ufdset, fdset, FDS_BYTES(nr));
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return 0;
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}
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static inline
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void zero_fd_set(unsigned long nr, unsigned long *fdset)
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{
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memset(fdset, 0, FDS_BYTES(nr));
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}
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#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
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extern int do_select(int n, fd_set_bits *fds, struct timespec *end_time);
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extern int do_sys_poll(struct pollfd __user * ufds, unsigned int nfds,
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struct timespec *end_time);
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extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
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fd_set __user *exp, struct timespec *end_time);
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extern int poll_select_set_timeout(struct timespec *to, long sec, long nsec);
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#endif /* KERNEL */
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#endif /* _LINUX_POLL_H */
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