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/*
 * Copyright (C) 2005-2006, Tobias Klauser <tklauser@distanz.ch>
 *
 * Licensed under the terms of the GNU General Public License; version 2 or later.
 */

#ifndef _INOTAIL_H
#define _INOTAIL_H

/* Number of items to tail. */
#define DEFAULT_N_LINES 10

/* tail modes */
enum { M_LINES, M_BYTES };

/* Every tailed file is represented as a file_struct */
struct file_struct {
	char *name;		/* Name of file (or '-' for stdin) */
	int fd;			/* File descriptor (or -1 if file is not open */
	off_t st_size;		/* File size */
	unsigned ignore;	/* Whether to ignore the file in further processing */
	int i_watch;		/* Inotify watch associated with file_struct */
};

#define IS_PIPELIKE(mode) \
	(S_ISFIFO(mode) || S_ISSOCK(mode))

/* inotail works on these file types */
#define IS_TAILABLE(mode) \
	(S_ISREG(mode) || IS_PIPELIKE(mode) || S_ISCHR(mode))

#ifdef DEBUG
# define dprintf(fmt, args...) fprintf(stderr, fmt, ##args)
#else
# define dprintf(fmt, args...)
#endif /* DEBUG */

#ifdef __GNUC__
# define unlikely(x) __builtin_expect(!!(x), 0)
#else
# define unlikely(x) (x)
#endif /* __GNUC__ */

#endif /* _INOTAIL_H */
ff)
blk-mq: implement hybrid poll mode for sync O_DIRECT
This patch enables a hybrid polling mode. Instead of polling after IO submission, we can induce an artificial delay, and then poll after that. For example, if the IO is presumed to complete in 8 usecs from now, we can sleep for 4 usecs, wake up, and then do our polling. This still puts a sleep/wakeup cycle in the IO path, but instead of the wakeup happening after the IO has completed, it'll happen before. With this hybrid scheme, we can achieve big latency reductions while still using the same (or less) amount of CPU. Signed-off-by: Jens Axboe <axboe@fb.com> Tested-By: Stephen Bates <sbates@raithlin.com> Reviewed-By: Stephen Bates <sbates@raithlin.com>
Diffstat (limited to 'block')