uvm_aobj.c

来自「基于组件方式开发操作系统的OSKIT源代码」· C语言 代码 · 共 1,553 行 · 第 1/3 页

/*	$NetBSD: uvm_aobj.c,v 1.37 2000/11/25 06:27:59 chs Exp $	*/

/*
 * Copyright (c) 1998 Chuck Silvers, Charles D. Cranor and
 *                    Washington University.
 * 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, 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Charles D. Cranor and
 *      Washington University.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * from: Id: uvm_aobj.c,v 1.1.2.5 1998/02/06 05:14:38 chs Exp
 */
/*
 * uvm_aobj.c: anonymous memory uvm_object pager
 *
 * author: Chuck Silvers <[e-mail]>
 * started: Jan-1998
 *
 * - design mostly from Chuck Cranor
 */



#include "opt_uvmhist.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/kernel.h>
#include <sys/pool.h>
#include <sys/kernel.h>

#include <uvm/uvm.h>

/*
 * an aobj manages anonymous-memory backed uvm_objects.   in addition
 * to keeping the list of resident pages, it also keeps a list of
 * allocated swap blocks.  depending on the size of the aobj this list
 * of allocated swap blocks is either stored in an array (small objects)
 * or in a hash table (large objects).
 */

/*
 * local structures
 */

/*
 * for hash tables, we break the address space of the aobj into blocks
 * of UAO_SWHASH_CLUSTER_SIZE pages.   we require the cluster size to
 * be a power of two.
 */

#define UAO_SWHASH_CLUSTER_SHIFT 4
#define UAO_SWHASH_CLUSTER_SIZE (1 << UAO_SWHASH_CLUSTER_SHIFT)

/* get the "tag" for this page index */
#define UAO_SWHASH_ELT_TAG(PAGEIDX) \
	((PAGEIDX) >> UAO_SWHASH_CLUSTER_SHIFT)

/* given an ELT and a page index, find the swap slot */
#define UAO_SWHASH_ELT_PAGESLOT(ELT, PAGEIDX) \
	((ELT)->slots[(PAGEIDX) & (UAO_SWHASH_CLUSTER_SIZE - 1)])

/* given an ELT, return its pageidx base */
#define UAO_SWHASH_ELT_PAGEIDX_BASE(ELT) \
	((ELT)->tag << UAO_SWHASH_CLUSTER_SHIFT)

/*
 * the swhash hash function
 */
#define UAO_SWHASH_HASH(AOBJ, PAGEIDX) \
	(&(AOBJ)->u_swhash[(((PAGEIDX) >> UAO_SWHASH_CLUSTER_SHIFT) \
			    & (AOBJ)->u_swhashmask)])

/*
 * the swhash threshhold determines if we will use an array or a
 * hash table to store the list of allocated swap blocks.
 */

#define UAO_SWHASH_THRESHOLD (UAO_SWHASH_CLUSTER_SIZE * 4)
#define UAO_USES_SWHASH(AOBJ) \
	((AOBJ)->u_pages > UAO_SWHASH_THRESHOLD)	/* use hash? */

/*
 * the number of buckets in a swhash, with an upper bound
 */
#define UAO_SWHASH_MAXBUCKETS 256
#define UAO_SWHASH_BUCKETS(AOBJ) \
	(min((AOBJ)->u_pages >> UAO_SWHASH_CLUSTER_SHIFT, \
	     UAO_SWHASH_MAXBUCKETS))


/*
 * uao_swhash_elt: when a hash table is being used, this structure defines
 * the format of an entry in the bucket list.
 */

struct uao_swhash_elt {
	LIST_ENTRY(uao_swhash_elt) list;	/* the hash list */
	voff_t tag;				/* our 'tag' */
	int count;				/* our number of active slots */
	int slots[UAO_SWHASH_CLUSTER_SIZE];	/* the slots */
};

/*
 * uao_swhash: the swap hash table structure
 */

LIST_HEAD(uao_swhash, uao_swhash_elt);

/*
 * uao_swhash_elt_pool: pool of uao_swhash_elt structures
 */

struct pool uao_swhash_elt_pool;

/*
 * uvm_aobj: the actual anon-backed uvm_object
 *
 * => the uvm_object is at the top of the structure, this allows
 *   (struct uvm_device *) == (struct uvm_object *)
 * => only one of u_swslots and u_swhash is used in any given aobj
 */

struct uvm_aobj {
	struct uvm_object u_obj; /* has: lock, pgops, memq, #pages, #refs */
	int u_pages;		 /* number of pages in entire object */
	int u_flags;		 /* the flags (see uvm_aobj.h) */
	int *u_swslots;		 /* array of offset->swapslot mappings */
				 /*
				  * hashtable of offset->swapslot mappings
				  * (u_swhash is an array of bucket heads)
				  */
	struct uao_swhash *u_swhash;
	u_long u_swhashmask;		/* mask for hashtable */
	LIST_ENTRY(uvm_aobj) u_list;	/* global list of aobjs */
};

/*
 * uvm_aobj_pool: pool of uvm_aobj structures
 */

struct pool uvm_aobj_pool;

/*
 * local functions
 */

static struct uao_swhash_elt	*uao_find_swhash_elt __P((struct uvm_aobj *,
							  int, boolean_t));
static int			 uao_find_swslot __P((struct uvm_aobj *, int));
static boolean_t		 uao_flush __P((struct uvm_object *,
						voff_t, voff_t, int));
static void			 uao_free __P((struct uvm_aobj *));
static int			 uao_get __P((struct uvm_object *, voff_t,
					      vm_page_t *, int *, int,
					      vm_prot_t, int, int));
static boolean_t		 uao_releasepg __P((struct vm_page *,
						    struct vm_page **));
static boolean_t		 uao_pagein __P((struct uvm_aobj *, int, int));
static boolean_t		 uao_pagein_page __P((struct uvm_aobj *, int));

/*
 * aobj_pager
 * 
 * note that some functions (e.g. put) are handled elsewhere
 */

struct uvm_pagerops aobj_pager = {
	NULL,			/* init */
	uao_reference,		/* reference */
	uao_detach,		/* detach */
	NULL,			/* fault */
	uao_flush,		/* flush */
	uao_get,		/* get */
	NULL,			/* put (done by pagedaemon) */
	NULL,			/* cluster */
	NULL,			/* mk_pcluster */
	uao_releasepg		/* releasepg */
};

/*
 * uao_list: global list of active aobjs, locked by uao_list_lock
 */

static LIST_HEAD(aobjlist, uvm_aobj) uao_list;
static simple_lock_data_t uao_list_lock;


/*
 * functions
 */

/*
 * hash table/array related functions
 */

/*
 * uao_find_swhash_elt: find (or create) a hash table entry for a page
 * offset.
 *
 * => the object should be locked by the caller
 */

static struct uao_swhash_elt *
uao_find_swhash_elt(aobj, pageidx, create)
	struct uvm_aobj *aobj;
	int pageidx;
	boolean_t create;
{
	struct uao_swhash *swhash;
	struct uao_swhash_elt *elt;
	voff_t page_tag;

	swhash = UAO_SWHASH_HASH(aobj, pageidx); /* first hash to get bucket */
	page_tag = UAO_SWHASH_ELT_TAG(pageidx);	/* tag to search for */

	/*
	 * now search the bucket for the requested tag
	 */
	LIST_FOREACH(elt, swhash, list) {
		if (elt->tag == page_tag)
			return(elt);
	}

	/* fail now if we are not allowed to create a new entry in the bucket */
	if (!create)
		return NULL;


	/*
	 * allocate a new entry for the bucket and init/insert it in
	 */
	elt = pool_get(&uao_swhash_elt_pool, PR_WAITOK);
	LIST_INSERT_HEAD(swhash, elt, list);
	elt->tag = page_tag;
	elt->count = 0;
	memset(elt->slots, 0, sizeof(elt->slots));

	return(elt);
}

/*
 * uao_find_swslot: find the swap slot number for an aobj/pageidx
 *
 * => object must be locked by caller 
 */
__inline static int
uao_find_swslot(aobj, pageidx)
	struct uvm_aobj *aobj;
	int pageidx;
{

	/*
	 * if noswap flag is set, then we never return a slot
	 */

	if (aobj->u_flags & UAO_FLAG_NOSWAP)
		return(0);

	/*
	 * if hashing, look in hash table.
	 */

	if (UAO_USES_SWHASH(aobj)) {
		struct uao_swhash_elt *elt =
		    uao_find_swhash_elt(aobj, pageidx, FALSE);

		if (elt)
			return(UAO_SWHASH_ELT_PAGESLOT(elt, pageidx));
		else
			return(0);
	}

	/* 
	 * otherwise, look in the array
	 */
	return(aobj->u_swslots[pageidx]);
}

/*
 * uao_set_swslot: set the swap slot for a page in an aobj.
 *
 * => setting a slot to zero frees the slot
 * => object must be locked by caller
 */
int
uao_set_swslot(uobj, pageidx, slot)
	struct uvm_object *uobj;
	int pageidx, slot;
{
	struct uvm_aobj *aobj = (struct uvm_aobj *)uobj;
	int oldslot;
	UVMHIST_FUNC("uao_set_swslot"); UVMHIST_CALLED(pdhist);
	UVMHIST_LOG(pdhist, "aobj %p pageidx %d slot %d",
	    aobj, pageidx, slot, 0);

	/*
	 * if noswap flag is set, then we can't set a slot
	 */

	if (aobj->u_flags & UAO_FLAG_NOSWAP) {

		if (slot == 0)
			return(0);		/* a clear is ok */

		/* but a set is not */
		printf("uao_set_swslot: uobj = %p\n", uobj);
	    panic("uao_set_swslot: attempt to set a slot on a NOSWAP object");
	}

	/*
	 * are we using a hash table?  if so, add it in the hash.
	 */

	if (UAO_USES_SWHASH(aobj)) {
		/*
		 * Avoid allocating an entry just to free it again if
		 * the page had not swap slot in the first place, and
		 * we are freeing.
		 */
		struct uao_swhash_elt *elt =
		    uao_find_swhash_elt(aobj, pageidx, slot ? TRUE : FALSE);
		if (elt == NULL) {
#ifdef DIAGNOSTIC
			if (slot)
				panic("uao_set_swslot: didn't create elt");
#endif
			return (0);
		}

		oldslot = UAO_SWHASH_ELT_PAGESLOT(elt, pageidx);
		UAO_SWHASH_ELT_PAGESLOT(elt, pageidx) = slot;

		/*
		 * now adjust the elt's reference counter and free it if we've
		 * dropped it to zero.
		 */

		/* an allocation? */
		if (slot) {
			if (oldslot == 0)
				elt->count++;
		} else {		/* freeing slot ... */
			if (oldslot)	/* to be safe */
				elt->count--;

			if (elt->count == 0) {
				LIST_REMOVE(elt, list);
				pool_put(&uao_swhash_elt_pool, elt);
			}
		}
	} else { 
		/* we are using an array */
		oldslot = aobj->u_swslots[pageidx];
		aobj->u_swslots[pageidx] = slot;
	}
	return (oldslot);
}

/*
 * end of hash/array functions
 */

/*
 * uao_free: free all resources held by an aobj, and then free the aobj
 *
 * => the aobj should be dead
 */
static void
uao_free(aobj)
	struct uvm_aobj *aobj;
{

	simple_unlock(&aobj->u_obj.vmobjlock);

	if (UAO_USES_SWHASH(aobj)) {
		int i, hashbuckets = aobj->u_swhashmask + 1;

		/*
		 * free the swslots from each hash bucket,
		 * then the hash bucket, and finally the hash table itself.
		 */
		for (i = 0; i < hashbuckets; i++) {
			struct uao_swhash_elt *elt, *next;

			for (elt = LIST_FIRST(&aobj->u_swhash[i]);
			     elt != NULL;
			     elt = next) {
				int j;

				for (j = 0; j < UAO_SWHASH_CLUSTER_SIZE; j++) {
					int slot = elt->slots[j];

					if (slot == 0) {
						continue;
					}
					uvm_swap_free(slot, 1);

					/*
					 * this page is no longer
					 * only in swap.
					 */
					simple_lock(&uvm.swap_data_lock);
					uvmexp.swpgonly--;
					simple_unlock(&uvm.swap_data_lock);
				}

				next = LIST_NEXT(elt, list);
				pool_put(&uao_swhash_elt_pool, elt);
			}
		}
		free(aobj->u_swhash, M_UVMAOBJ);
	} else {
		int i;

		/*
		 * free the array
		 */

		for (i = 0; i < aobj->u_pages; i++) {
			int slot = aobj->u_swslots[i];

			if (slot) {
				uvm_swap_free(slot, 1);

				/* this page is no longer only in swap. */
				simple_lock(&uvm.swap_data_lock);
				uvmexp.swpgonly--;
				simple_unlock(&uvm.swap_data_lock);
			}
		}
		free(aobj->u_swslots, M_UVMAOBJ);
	}

	/*
	 * finally free the aobj itself
	 */
	pool_put(&uvm_aobj_pool, aobj);
}

/*
 * pager functions
 */

/*
 * uao_create: create an aobj of the given size and return its uvm_object.
 *
 * => for normal use, flags are always zero
 * => for the kernel object, the flags are:
 *	UAO_FLAG_KERNOBJ - allocate the kernel object (can only happen once)
 *	UAO_FLAG_KERNSWAP - enable swapping of kernel object ("           ")
 */
struct uvm_object *
uao_create(size, flags)
	vsize_t size;
	int flags;
{
	static struct uvm_aobj kernel_object_store; /* home of kernel_object */
	static int kobj_alloced = 0;			/* not allocated yet */
	int pages = round_page(size) >> PAGE_SHIFT;
	struct uvm_aobj *aobj;

	/*
	 * malloc a new aobj unless we are asked for the kernel object
	 */
	if (flags & UAO_FLAG_KERNOBJ) {		/* want kernel object? */
		if (kobj_alloced)
			panic("uao_create: kernel object already allocated");

		aobj = &kernel_object_store;
		aobj->u_pages = pages;
		aobj->u_flags = UAO_FLAG_NOSWAP;	/* no swap to start */
		/* we are special, we never die */
		aobj->u_obj.uo_refs = UVM_OBJ_KERN;
		kobj_alloced = UAO_FLAG_KERNOBJ;
	} else if (flags & UAO_FLAG_KERNSWAP) {
		aobj = &kernel_object_store;
		if (kobj_alloced != UAO_FLAG_KERNOBJ)
		    panic("uao_create: asked to enable swap on kernel object");
		kobj_alloced = UAO_FLAG_KERNSWAP;
	} else {	/* normal object */
		aobj = pool_get(&uvm_aobj_pool, PR_WAITOK);
		aobj->u_pages = pages;
		aobj->u_flags = 0;		/* normal object */
		aobj->u_obj.uo_refs = 1;	/* start with 1 reference */
	}

	/*
 	 * allocate hash/array if necessary
 	 *
 	 * note: in the KERNSWAP case no need to worry about locking since
 	 * we are still booting we should be the only thread around.
 	 */