File:  [DragonFly] / src / sys / sys / pipe.h
Revision 1.4: download - view: text, annotated - select for diffs
Sun Mar 28 08:25:46 2004 UTC (10 years, 5 months ago) by dillon
Branches: MAIN
CVS tags: HEAD
Import Alan Cox's /usr/src/sys/kern/sys_pipe.c 1.171.  This rips out
writer-side KVA mappings and replaces them with writer-side vm_page wiring
(left intact from before) plus reader-side SF_BUF copies.

Import 1.141, which is a simple patch which removes a blocking condition
when space is available in the pipe's write buffer which was causing
non-blocking I/O select-based writes to spin-wait unnecessarily.  1.171
rips out writer-side KVA mappings and replaces them

Import FreeBSD-5.x's uiomove_fromphys(), which sys_pipe.c now uses.  This
procedure could become very useful in a number of DragonFly subsystems.

This greatly improves PIPE performance for the direct-mapped case (moderate
to large reads and writes).  Additionally, recent scheduler fixes greatly
improve PIPE performance for both the direct-mapped and small-buffer cases.

NOTE: wired page limits for pipes have not yet been imported, and the heavy
use of sf_buf's may require some tuning in the many-pipes case.


    BLKSIZE	BEFORE		AFTER
		MBytes/s	MBytes/s	Tests on AMD64/3200+ FN85 MB
    -------	------		------		(64KB L1, 1MB L2)
    256KB	1900		2200
     64KB	1800		2200
     16KB	1650		2500-3000
      8KB	1400		2300
      4KB	1300		1400-1500	(note 1)

    note 1: The 4KB case is not a direct-write case, the results are due to
    the scheduler fixes only.


Obtained-from: FreeBSD-5.x / FreeBSD's Alan Cox

/*
 * Copyright (c) 1996 John S. Dyson
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice immediately at the beginning of the file, without modification,
 *    this list of conditions, and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Absolutely no warranty of function or purpose is made by the author
 *    John S. Dyson.
 * 4. This work was done expressly for inclusion into FreeBSD.  Other use
 *    is allowed if this notation is included.
 * 5. Modifications may be freely made to this file if the above conditions
 *    are met.
 *
 * $FreeBSD: src/sys/sys/pipe.h,v 1.16 1999/12/29 04:24:45 peter Exp $
 * $DragonFly: src/sys/sys/pipe.h,v 1.4 2004/03/28 08:25:46 dillon Exp $
 */

#ifndef _SYS_PIPE_H_
#define _SYS_PIPE_H_

#ifndef _KERNEL
#include <sys/time.h>			/* for struct timespec */
#include <sys/select.h>			/* for struct selinfo */
#include <vm/vm.h>			/* for vm_page_t */
#include <machine/param.h>		/* for PAGE_SIZE */
#endif

/*
 * Pipe buffer size, keep moderate in value, pipes take kva space.
 */
#ifndef PIPE_SIZE
#define PIPE_SIZE	16384
#endif

#ifndef BIG_PIPE_SIZE
#define BIG_PIPE_SIZE	(64*1024)
#endif

/*
 * PIPE_MINDIRECT MUST be smaller than PIPE_SIZE and MUST be bigger
 * than PIPE_BUF.
 */
#ifndef PIPE_MINDIRECT
#define PIPE_MINDIRECT	8192
#endif

#define PIPENPAGES	(BIG_PIPE_SIZE / PAGE_SIZE + 1)

/*
 * Pipe buffer information.
 * Separate in, out, cnt are used to simplify calculations.
 * Buffered write is active when the buffer.cnt field is set.
 */
struct pipebuf {
	u_int	cnt;		/* number of chars currently in buffer */
	u_int	in;		/* in pointer */
	u_int	out;		/* out pointer */
	u_int	size;		/* size of buffer */
	caddr_t	buffer;		/* kva of buffer */
	struct  vm_object *object;	/* VM object containing buffer */
};

/*
 * Information to support direct transfers between processes for pipes.
 */
struct pipemapping {
	vm_size_t	cnt;		/* number of chars in buffer */
	vm_size_t	pos;		/* current position of transfer */
	int		npages;		/* number of pages */
	vm_page_t	ms[PIPENPAGES];	/* pages in source process */
};

/*
 * Bits in pipe_state.
 */
#define PIPE_ASYNC	0x004	/* Async? I/O. */
#define PIPE_WANTR	0x008	/* Reader wants some characters. */
#define PIPE_WANTW	0x010	/* Writer wants space to put characters. */
#define PIPE_WANT	0x020	/* Pipe is wanted to be run-down. */
#define PIPE_SEL	0x040	/* Pipe has a select active. */
#define PIPE_EOF	0x080	/* Pipe is in EOF condition. */
#define PIPE_LOCK	0x100	/* Process has exclusive access to pointers/data. */
#define PIPE_LWANT	0x200	/* Process wants exclusive access to pointers/data. */
#define PIPE_DIRECTW	0x400	/* Pipe direct write active. */
#define PIPE_DIRECTOK	0x800	/* Direct mode ok. */

/*
 * Per-pipe data structure.
 * Two of these are linked together to produce bi-directional pipes.
 */
struct pipe {
	struct	pipebuf pipe_buffer;	/* data storage */
	struct	pipemapping pipe_map;	/* pipe mapping for direct I/O */
	struct	selinfo pipe_sel;	/* for compat with select */
	struct	timespec pipe_atime;	/* time of last access */
	struct	timespec pipe_mtime;	/* time of last modify */
	struct	timespec pipe_ctime;	/* time of status change */
	struct	sigio *pipe_sigio;	/* information for async I/O */
	struct	pipe *pipe_peer;	/* link with other direction */
	u_int	pipe_state;		/* pipe status info */
	int	pipe_busy;		/* busy flag, mostly to handle rundown sanely */
};

#endif /* !_SYS_PIPE_H_ */