[unix-history] / sys / kern / kern_malloc.c

/*
 * Copyright (c) 1987, 1991 The Regents of the University of California.
 * 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 the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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: @(#)kern_malloc.c	7.25 (Berkeley) 5/8/91
 *	$Id: kern_malloc.c,v 1.8 1994/02/10 08:04:07 davidg Exp $
 */

#include "param.h"
#include "systm.h"
#include "proc.h"
#include "kernel.h"
#include "malloc.h"
#include "vm/vm.h"
#include "vm/vm_kern.h"

extern int vm_page_count;

struct kmembuckets bucket[MINBUCKET + 16];
struct kmemstats kmemstats[M_LAST];
struct kmemusage *kmemusage;
char *kmembase, *kmemlimit;
char *memname[] = INITKMEMNAMES;

/*
 * Allocate a block of memory
 */
void *
malloc(size, type, flags)
	unsigned long size;
	int type, flags;
{
	register struct kmembuckets *kbp;
	register struct kmemusage *kup;
	long indx, npg, alloc, allocsize;
	int s;
	caddr_t va, cp, savedlist;
#ifdef KMEMSTATS
	register struct kmemstats *ksp = &kmemstats[type];

	if (((unsigned long)type) >= M_LAST)
		panic("malloc - bogus type");
#endif

	indx = BUCKETINDX(size);
	kbp = &bucket[indx];
	s = splimp();
#ifdef KMEMSTATS
	while (ksp->ks_memuse >= ksp->ks_limit) {
		if (flags & M_NOWAIT) {
			splx(s);
			return ((void *) NULL);
		}
		if (ksp->ks_limblocks < 65535)
			ksp->ks_limblocks++;
		tsleep((caddr_t)ksp, PSWP+2, memname[type], 0);
	}
#endif
	if (kbp->kb_next == NULL) {
		if (size > MAXALLOCSAVE)
			allocsize = roundup(size, CLBYTES);
		else
			allocsize = 1 << indx;
		npg = clrnd(btoc(allocsize));
		va = (caddr_t) kmem_malloc(kmem_map, (vm_size_t)ctob(npg),
					   !(flags & M_NOWAIT));
		if (va == NULL) {
			splx(s);
			return ((void *) NULL);
		}
#ifdef KMEMSTATS
		kbp->kb_total += kbp->kb_elmpercl;
#endif
		kup = btokup(va);
		kup->ku_indx = indx;
		if (allocsize > MAXALLOCSAVE) {
			if (npg > 65535)
				panic("malloc: allocation too large");
			kup->ku_pagecnt = npg;
#ifdef KMEMSTATS
			ksp->ks_memuse += allocsize;
#endif
			goto out;
		}
#ifdef KMEMSTATS
		kup->ku_freecnt = kbp->kb_elmpercl;
		kbp->kb_totalfree += kbp->kb_elmpercl;
#endif
		/*
		 * Just in case we blocked while allocating memory,
		 * and someone else also allocated memory for this
		 * bucket, don't assume the list is still empty.
		 */
		savedlist = kbp->kb_next;
		kbp->kb_next = va + (npg * NBPG) - allocsize;
		for (cp = kbp->kb_next; cp > va; cp -= allocsize)
			*(caddr_t *)cp = cp - allocsize;
		*(caddr_t *)cp = savedlist;
	}
	va = kbp->kb_next;
	kbp->kb_next = *(caddr_t *)va;
#ifdef KMEMSTATS
	kup = btokup(va);
	if (kup->ku_indx != indx)
		panic("malloc: wrong bucket");
	if (kup->ku_freecnt == 0)
		panic("malloc: lost data");
	kup->ku_freecnt--;
	kbp->kb_totalfree--;
	ksp->ks_memuse += 1 << indx;
out:
	kbp->kb_calls++;
	ksp->ks_inuse++;
	ksp->ks_calls++;
	if (ksp->ks_memuse > ksp->ks_maxused)
		ksp->ks_maxused = ksp->ks_memuse;
#else
out:
#endif
	splx(s);
	return ((void *) va);
}

#ifdef DIAGNOSTIC
long addrmask[] = { 0x00000000,
	0x00000001, 0x00000003, 0x00000007, 0x0000000f,
	0x0000001f, 0x0000003f, 0x0000007f, 0x000000ff,
	0x000001ff, 0x000003ff, 0x000007ff, 0x00000fff,
	0x00001fff, 0x00003fff, 0x00007fff, 0x0000ffff,
};
#endif /* DIAGNOSTIC */

/*
 * Free a block of memory allocated by malloc.
 */
void
free(addr, type)
	void *addr;
	int type;
{
	register struct kmembuckets *kbp;
	register struct kmemusage *kup;
	long alloc, size;
	int s;
#ifdef KMEMSTATS
	register struct kmemstats *ksp = &kmemstats[type];
#endif

	kup = btokup(addr);
	size = 1 << kup->ku_indx;
#ifdef DIAGNOSTIC
	if (size > NBPG * CLSIZE)
		alloc = addrmask[BUCKETINDX(NBPG * CLSIZE)];
	else
		alloc = addrmask[kup->ku_indx];
	if (((u_long)addr & alloc) != 0) {
		printf("free: unaligned addr 0x%x, size %d, type %d, mask %d\n",
			addr, size, type, alloc);
		panic("free: unaligned addr");
	}
#endif /* DIAGNOSTIC */
	kbp = &bucket[kup->ku_indx];
	s = splimp();
	if (size > MAXALLOCSAVE) {
		kmem_free(kmem_map, (vm_offset_t)addr, ctob(kup->ku_pagecnt));
#ifdef KMEMSTATS
		size = kup->ku_pagecnt << PGSHIFT;
		ksp->ks_memuse -= size;
		kup->ku_indx = 0;
		kup->ku_pagecnt = 0;
		if (ksp->ks_memuse + size >= ksp->ks_limit &&
		    ksp->ks_memuse < ksp->ks_limit)
			wakeup((caddr_t)ksp);
		ksp->ks_inuse--;
		kbp->kb_total -= 1;
#endif
		splx(s);
		return;
	}
#ifdef KMEMSTATS
	kup->ku_freecnt++;
	if (kup->ku_freecnt >= kbp->kb_elmpercl)
		if (kup->ku_freecnt > kbp->kb_elmpercl)
			panic("free: multiple frees");
		else if (kbp->kb_totalfree > kbp->kb_highwat)
			kbp->kb_couldfree++;
	kbp->kb_totalfree++;
	ksp->ks_memuse -= size;
	if (ksp->ks_memuse + size >= ksp->ks_limit &&
	    ksp->ks_memuse < ksp->ks_limit)
		wakeup((caddr_t)ksp);
	ksp->ks_inuse--;
#endif
	*(caddr_t *)addr = kbp->kb_next;
	kbp->kb_next = addr;
	splx(s);
}

/*
 * Initialize the kernel memory allocator
 */
void
kmeminit()
{
	register long indx;
	int npg;

#if	(MAXALLOCSAVE > MINALLOCSIZE * 32768)
#  error "kmeminit: MAXALLOCSAVE too big"
#endif
#if	(MAXALLOCSAVE < CLBYTES-1)
#  error "kmeminit: MAXALLOCSAVE too small"
#endif
	npg = (VM_KMEM_SIZE + VM_MBUF_SIZE) / NBPG;
	kmemusage = (struct kmemusage *) kmem_alloc(kernel_map,
		(vm_size_t)(npg * sizeof(struct kmemusage)));
	kmem_map = kmem_suballoc(kernel_map, (vm_offset_t *)&kmembase,
		(vm_offset_t *)&kmemlimit, (vm_size_t)(npg * NBPG), FALSE);
#ifdef KMEMSTATS
	for (indx = 0; indx < MINBUCKET + 16; indx++) {
		if (1 << indx >= CLBYTES)
			bucket[indx].kb_elmpercl = 1;
		else
			bucket[indx].kb_elmpercl = CLBYTES / (1 << indx);
		bucket[indx].kb_highwat = 5 * bucket[indx].kb_elmpercl;
	}
	for (indx = 0; indx < M_LAST; indx++)
		kmemstats[indx].ks_limit = npg * NBPG * 6 / 10;

	/* limit the amount of mbuf space to 1/16 of system memory */
	kmemstats[M_MBUF].ks_limit = (vm_page_count * NBPG) / 16;
#endif
}

void *
contigmalloc(size, type, flags, maxpa, alignmask, boundarymask)
	unsigned long size;
	int type;
	int flags;
	unsigned long maxpa;		/* e.g. 16M - 1 for isa dma */
	unsigned long alignmask;	/* e.g. 1M - 1 for M boundary */
	unsigned long boundarymask;	/* e.g. 64K - 1 for 8-bit isa dma */
{
	unsigned long skipsize;
	void *skipva;

	size = round_page(size);
	if (size == 0 || size > boundarymask + 1)
		return (NULL);

	/*
	 * Attempt to push the physical address to a suitable boundary by
	 * skipping some memory.  We could be cleverer here.  E.g., mallocate
	 * lots of single pages and then free the ones that we hope to use.
	 * flags == M_WAIT is likely to hang the system.
	 */
	for (skipsize = 0, skipva = NULL; ; skipsize += NBPG) {
		unsigned long off;
		unsigned long pa;
		unsigned long prevpa;
		void *va;

		if (skipsize != 0) {
			skipva = malloc(skipsize, type, flags);
			if (skipva == NULL) {
#ifdef DEBUG
				printf("contigmalloc: skipva NULL on try %d\n",
				       1 + skipsize / NBPG);
#endif
				return (NULL);
			}
		}
		va = malloc(size, type, flags);
		if (skipsize != 0)
			free(skipva, type);
		if (va == NULL) {
#ifdef DEBUG
			printf("contigmalloc: va NULL on try %d\n",
			       1 + skipsize / NBPG);
#endif
			return (NULL);
		}
		for (off = 0, prevpa = 0; off < size; off += NBPG, prevpa = pa)
		{
			pa = pmap_extract(pmap_kernel(), (vm_offset_t)va + off);
			if (pa + NBPG - 1 > maxpa
			    || off == 0 && pa & alignmask
			    || off != 0
			       && (pa != prevpa + NBPG
				   || (pa & boundarymask) == 0))
				goto fail;
		}
#ifdef DEBUG
		printf("contigmalloc: success at va %lx pa %lx on try %d\n",
		       (unsigned long)va,
		       pmap_extract(pmap_kernel(), (unsigned long)va),
		       1 + skipsize / NBPG);
#endif
		return (va);
fail:
		free(va, type);
	}
}
Commit	Line	Data
15637ed4 RG	1	/*
	2	* Copyright (c) 1987, 1991 The Regents of the University of California.
	3	* All rights reserved.
	4	*
	5	* Redistribution and use in source and binary forms, with or without
	6	* modification, are permitted provided that the following conditions
	7	* are met:
	8	* 1. Redistributions of source code must retain the above copyright
	9	* notice, this list of conditions and the following disclaimer.
	10	* 2. Redistributions in binary form must reproduce the above copyright
	11	* notice, this list of conditions and the following disclaimer in the
	12	* documentation and/or other materials provided with the distribution.
	13	* 3. All advertising materials mentioning features or use of this software
	14	* must display the following acknowledgement:
	15	* This product includes software developed by the University of
	16	* California, Berkeley and its contributors.
	17	* 4. Neither the name of the University nor the names of its contributors
	18	* may be used to endorse or promote products derived from this software
	19	* without specific prior written permission.
	20	*
	21	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	22	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	23	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	24	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	25	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	26	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	27	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	28	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	29	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	30	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	31	* SUCH DAMAGE.
	32	*
600f7f07	33	* from: @(#)kern_malloc.c 7.25 (Berkeley) 5/8/91
e8bbcc37	34	* $Id: kern_malloc.c,v 1.8 1994/02/10 08:04:07 davidg Exp $
15637ed4 RG	35	*/
	36
	37	#include "param.h"
4c45483e	38	#include "systm.h"
15637ed4 RG	39	#include "proc.h"
	40	#include "kernel.h"
	41	#include "malloc.h"
	42	#include "vm/vm.h"
	43	#include "vm/vm_kern.h"
	44
9b9ba645 DG	45	extern int vm_page_count;
9b9ba645 DG	46
15637ed4 RG	47	struct kmembuckets bucket[MINBUCKET + 16];
	48	struct kmemstats kmemstats[M_LAST];
	49	struct kmemusage *kmemusage;
	50	char kmembase, kmemlimit;
	51	char *memname[] = INITKMEMNAMES;
	52
	53	/*
	54	* Allocate a block of memory
	55	*/
	56	void *
	57	malloc(size, type, flags)
	58	unsigned long size;
	59	int type, flags;
	60	{
	61	register struct kmembuckets *kbp;
	62	register struct kmemusage *kup;
	63	long indx, npg, alloc, allocsize;
	64	int s;
	65	caddr_t va, cp, savedlist;
	66	#ifdef KMEMSTATS
	67	register struct kmemstats *ksp = &kmemstats[type];
	68
c138d68d	69	if (((unsigned long)type) >= M_LAST)
15637ed4 RG	70	panic("malloc - bogus type");
	71	#endif
	72
	73	indx = BUCKETINDX(size);
	74	kbp = &bucket[indx];
	75	s = splimp();
	76	#ifdef KMEMSTATS
	77	while (ksp->ks_memuse >= ksp->ks_limit) {
	78	if (flags & M_NOWAIT) {
	79	splx(s);
	80	return ((void *) NULL);
	81	}
	82	if (ksp->ks_limblocks < 65535)
	83	ksp->ks_limblocks++;
	84	tsleep((caddr_t)ksp, PSWP+2, memname[type], 0);
	85	}
	86	#endif
	87	if (kbp->kb_next == NULL) {
	88	if (size > MAXALLOCSAVE)
	89	allocsize = roundup(size, CLBYTES);
	90	else
	91	allocsize = 1 << indx;
	92	npg = clrnd(btoc(allocsize));
	93	va = (caddr_t) kmem_malloc(kmem_map, (vm_size_t)ctob(npg),
	94	!(flags & M_NOWAIT));
	95	if (va == NULL) {
	96	splx(s);
	97	return ((void *) NULL);
	98	}
	99	#ifdef KMEMSTATS
	100	kbp->kb_total += kbp->kb_elmpercl;
	101	#endif
	102	kup = btokup(va);
	103	kup->ku_indx = indx;
	104	if (allocsize > MAXALLOCSAVE) {
	105	if (npg > 65535)
	106	panic("malloc: allocation too large");
	107	kup->ku_pagecnt = npg;
	108	#ifdef KMEMSTATS
	109	ksp->ks_memuse += allocsize;
	110	#endif
	111	goto out;
	112	}
	113	#ifdef KMEMSTATS
	114	kup->ku_freecnt = kbp->kb_elmpercl;
	115	kbp->kb_totalfree += kbp->kb_elmpercl;
	116	#endif
	117	/*
	118	* Just in case we blocked while allocating memory,
	119	* and someone else also allocated memory for this
	120	* bucket, don't assume the list is still empty.
	121	*/
	122	savedlist = kbp->kb_next;
	123	kbp->kb_next = va + (npg * NBPG) - allocsize;
	124	for (cp = kbp->kb_next; cp > va; cp -= allocsize)
	125	(caddr_t )cp = cp - allocsize;
	126	(caddr_t )cp = savedlist;
	127	}
	128	va = kbp->kb_next;
	129	kbp->kb_next = (caddr_t )va;
	130	#ifdef KMEMSTATS
	131	kup = btokup(va);
	132	if (kup->ku_indx != indx)
	133	panic("malloc: wrong bucket");
134	if (kup->ku_freecnt == 0)
135	panic("malloc: lost data");
136	kup->ku_freecnt--;
137	kbp->kb_totalfree--;
138	ksp->ks_memuse += 1 << indx;
139	out:
140	kbp->kb_calls++;
141	ksp->ks_inuse++;
142	ksp->ks_calls++;
143	if (ksp->ks_memuse > ksp->ks_maxused)
144	ksp->ks_maxused = ksp->ks_memuse;
145	#else
146	out:
147	#endif
148	splx(s);
149	return ((void *) va);
150	}
151
152	#ifdef DIAGNOSTIC
153	long addrmask[] = { 0x00000000,
154	0x00000001, 0x00000003, 0x00000007, 0x0000000f,
155	0x0000001f, 0x0000003f, 0x0000007f, 0x000000ff,
156	0x000001ff, 0x000003ff, 0x000007ff, 0x00000fff,
157	0x00001fff, 0x00003fff, 0x00007fff, 0x0000ffff,
158	};
159	#endif /* DIAGNOSTIC */
160
161	/*
162	* Free a block of memory allocated by malloc.
163	*/
164	void
165	free(addr, type)
166	void *addr;
167	int type;
168	{
169	register struct kmembuckets *kbp;
170	register struct kmemusage *kup;
171	long alloc, size;
172	int s;
173	#ifdef KMEMSTATS
174	register struct kmemstats *ksp = &kmemstats[type];
175	#endif
176
177	kup = btokup(addr);
178	size = 1 << kup->ku_indx;
179	#ifdef DIAGNOSTIC
180	if (size > NBPG * CLSIZE)
181	alloc = addrmask[BUCKETINDX(NBPG * CLSIZE)];
182	else
183	alloc = addrmask[kup->ku_indx];
184	if (((u_long)addr & alloc) != 0) {
185	printf("free: unaligned addr 0x%x, size %d, type %d, mask %d\n",
186	addr, size, type, alloc);
187	panic("free: unaligned addr");
188	}
189	#endif /* DIAGNOSTIC */
190	kbp = &bucket[kup->ku_indx];
191	s = splimp();
192	if (size > MAXALLOCSAVE) {
193	kmem_free(kmem_map, (vm_offset_t)addr, ctob(kup->ku_pagecnt));
194	#ifdef KMEMSTATS
195	size = kup->ku_pagecnt << PGSHIFT;
196	ksp->ks_memuse -= size;
197	kup->ku_indx = 0;
198	kup->ku_pagecnt = 0;
199	if (ksp->ks_memuse + size >= ksp->ks_limit &&
200	ksp->ks_memuse < ksp->ks_limit)
201	wakeup((caddr_t)ksp);
202	ksp->ks_inuse--;
203	kbp->kb_total -= 1;
204	#endif
205	splx(s);
206	return;
207	}
208	#ifdef KMEMSTATS
209	kup->ku_freecnt++;
210	if (kup->ku_freecnt >= kbp->kb_elmpercl)
211	if (kup->ku_freecnt > kbp->kb_elmpercl)
212	panic("free: multiple frees");
213	else if (kbp->kb_totalfree > kbp->kb_highwat)
214	kbp->kb_couldfree++;
215	kbp->kb_totalfree++;
216	ksp->ks_memuse -= size;
217	if (ksp->ks_memuse + size >= ksp->ks_limit &&
218	ksp->ks_memuse < ksp->ks_limit)
219	wakeup((caddr_t)ksp);
220	ksp->ks_inuse--;
221	#endif
222	(caddr_t )addr = kbp->kb_next;
223	kbp->kb_next = addr;
224	splx(s);
225	}
226
227	/*
228	* Initialize the kernel memory allocator
229	*/
4c45483e	230	void
15637ed4 RG	231	kmeminit()
	232	{
	233	register long indx;
	234	int npg;
	235
15637ed4	236	#if (MAXALLOCSAVE > MINALLOCSIZE * 32768)
4c45483e	237	# error "kmeminit: MAXALLOCSAVE too big"
15637ed4	238	#endif
d8bca54c	239	#if (MAXALLOCSAVE < CLBYTES-1)
4c45483e	240	# error "kmeminit: MAXALLOCSAVE too small"
15637ed4	241	#endif
1d7f5b47	242	npg = (VM_KMEM_SIZE + VM_MBUF_SIZE) / NBPG;
15637ed4 RG	243	kmemusage = (struct kmemusage *) kmem_alloc(kernel_map,
	244	(vm_size_t)(npg * sizeof(struct kmemusage)));
	245	kmem_map = kmem_suballoc(kernel_map, (vm_offset_t *)&kmembase,
	246	(vm_offset_t )&kmemlimit, (vm_size_t)(npg NBPG), FALSE);
	247	#ifdef KMEMSTATS
	248	for (indx = 0; indx < MINBUCKET + 16; indx++) {
	249	if (1 << indx >= CLBYTES)
	250	bucket[indx].kb_elmpercl = 1;
	251	else
	252	bucket[indx].kb_elmpercl = CLBYTES / (1 << indx);
	253	bucket[indx].kb_highwat = 5 * bucket[indx].kb_elmpercl;
	254	}
	255	for (indx = 0; indx < M_LAST; indx++)
	256	kmemstats[indx].ks_limit = npg * NBPG * 6 / 10;
b6e80617 DG	257
	258	/* limit the amount of mbuf space to 1/16 of system memory */
	259	kmemstats[M_MBUF].ks_limit = (vm_page_count * NBPG) / 16;
15637ed4 RG	260	#endif
15637ed4 RG	261	}
e8bbcc37 AC	262
	263	void *
	264	contigmalloc(size, type, flags, maxpa, alignmask, boundarymask)
	265	unsigned long size;
	266	int type;
	267	int flags;
	268	unsigned long maxpa; /* e.g. 16M - 1 for isa dma */
	269	unsigned long alignmask; /* e.g. 1M - 1 for M boundary */
	270	unsigned long boundarymask; /* e.g. 64K - 1 for 8-bit isa dma */
	271	{
	272	unsigned long skipsize;
	273	void *skipva;
	274
	275	size = round_page(size);
	276	if (size == 0 \|\| size > boundarymask + 1)
	277	return (NULL);
	278
	279	/*
	280	* Attempt to push the physical address to a suitable boundary by
	281	* skipping some memory. We could be cleverer here. E.g., mallocate
	282	* lots of single pages and then free the ones that we hope to use.
	283	* flags == M_WAIT is likely to hang the system.
	284	*/
	285	for (skipsize = 0, skipva = NULL; ; skipsize += NBPG) {
	286	unsigned long off;
	287	unsigned long pa;
	288	unsigned long prevpa;
	289	void *va;
	290
	291	if (skipsize != 0) {
	292	skipva = malloc(skipsize, type, flags);
	293	if (skipva == NULL) {
	294	#ifdef DEBUG
	295	printf("contigmalloc: skipva NULL on try %d\n",
	296	1 + skipsize / NBPG);
	297	#endif
	298	return (NULL);
	299	}
	300	}
	301	va = malloc(size, type, flags);
	302	if (skipsize != 0)
	303	free(skipva, type);
	304	if (va == NULL) {
	305	#ifdef DEBUG
	306	printf("contigmalloc: va NULL on try %d\n",
	307	1 + skipsize / NBPG);
	308	#endif
	309	return (NULL);
	310	}
	311	for (off = 0, prevpa = 0; off < size; off += NBPG, prevpa = pa)
	312	{
	313	pa = pmap_extract(pmap_kernel(), (vm_offset_t)va + off);
	314	if (pa + NBPG - 1 > maxpa
	315	\|\| off == 0 && pa & alignmask
	316	\|\| off != 0
	317	&& (pa != prevpa + NBPG
	318	\|\| (pa & boundarymask) == 0))
	319	goto fail;
	320	}
	321	#ifdef DEBUG
	322	printf("contigmalloc: success at va %lx pa %lx on try %d\n",
	323	(unsigned long)va,
	324	pmap_extract(pmap_kernel(), (unsigned long)va),
	325	1 + skipsize / NBPG);
326	#endif
327	return (va);
328	fail:
329	free(va, type);
330	}
331	}
332
333