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Date:      Fri, 28 Jun 2013 03:51:21 +0000 (UTC)
From:      Jeff Roberson <jeff@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r252330 - in head/sys: conf geom kern sys vm
Message-ID:  <201306280351.r5S3pLAm098083@svn.freebsd.org>

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Author: jeff
Date: Fri Jun 28 03:51:20 2013
New Revision: 252330
URL: http://svnweb.freebsd.org/changeset/base/252330

Log:
   - Add a general purpose resource allocator, vmem, from NetBSD.  It was
     originally inspired by the Solaris vmem detailed in the proceedings
     of usenix 2001.  The NetBSD version was heavily refactored for bugs
     and simplicity.
   - Use this resource allocator to allocate the buffer and transient maps.
     Buffer cache defrags are reduced by 25% when used by filesystems with
     mixed block sizes.  Ultimately this may permit dynamic buffer cache
     sizing on low KVA machines.
  
  Discussed with:	alc, kib, attilio
  Tested by:	pho
  Sponsored by:	EMC / Isilon Storage Division

Added:
  head/sys/kern/subr_vmem.c   (contents, props changed)
  head/sys/sys/vmem.h   (contents, props changed)
Modified:
  head/sys/conf/files
  head/sys/geom/geom_io.c
  head/sys/kern/vfs_bio.c
  head/sys/sys/malloc.h
  head/sys/vm/vm.h
  head/sys/vm/vm_init.c
  head/sys/vm/vm_kern.c
  head/sys/vm/vm_kern.h
  head/sys/vm/vm_object.c
  head/sys/vm/vm_pager.c
  head/sys/vm/vm_pager.h

Modified: head/sys/conf/files
==============================================================================
--- head/sys/conf/files	Fri Jun 28 03:41:23 2013	(r252329)
+++ head/sys/conf/files	Fri Jun 28 03:51:20 2013	(r252330)
@@ -2797,6 +2797,7 @@ kern/subr_trap.c		standard
 kern/subr_turnstile.c		standard
 kern/subr_uio.c			standard
 kern/subr_unit.c		standard
+kern/subr_vmem.c		standard
 kern/subr_witness.c		optional witness
 kern/sys_capability.c		standard
 kern/sys_generic.c		standard

Modified: head/sys/geom/geom_io.c
==============================================================================
--- head/sys/geom/geom_io.c	Fri Jun 28 03:41:23 2013	(r252329)
+++ head/sys/geom/geom_io.c	Fri Jun 28 03:51:20 2013	(r252330)
@@ -49,6 +49,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/proc.h>
 #include <sys/stack.h>
 #include <sys/sysctl.h>
+#include <sys/vmem.h>
 
 #include <sys/errno.h>
 #include <geom/geom.h>
@@ -626,7 +627,6 @@ g_io_transient_map_bio(struct bio *bp)
 	vm_offset_t addr;
 	long size;
 	u_int retried;
-	int rv;
 
 	KASSERT(unmapped_buf_allowed, ("unmapped disabled"));
 
@@ -636,10 +636,7 @@ g_io_transient_map_bio(struct bio *bp)
 	retried = 0;
 	atomic_add_long(&transient_maps, 1);
 retry:
-	vm_map_lock(bio_transient_map);
-	if (vm_map_findspace(bio_transient_map, vm_map_min(bio_transient_map),
-	    size, &addr)) {
-		vm_map_unlock(bio_transient_map);
+	if (vmem_alloc(transient_arena, size, M_BESTFIT | M_NOWAIT, &addr)) {
 		if (transient_map_retries != 0 &&
 		    retried >= transient_map_retries) {
 			g_io_deliver(bp, EDEADLK/* XXXKIB */);
@@ -651,7 +648,7 @@ retry:
 			/*
 			 * Naive attempt to quisce the I/O to get more
 			 * in-flight requests completed and defragment
-			 * the bio_transient_map.
+			 * the transient_arena.
 			 */
 			CTR3(KTR_GEOM, "g_down retrymap bp %p provider %s r %d",
 			    bp, bp->bio_to->name, retried);
@@ -661,12 +658,6 @@ retry:
 			goto retry;
 		}
 	}
-	rv = vm_map_insert(bio_transient_map, NULL, 0, addr, addr + size,
-	    VM_PROT_RW, VM_PROT_RW, MAP_NOFAULT);
-	KASSERT(rv == KERN_SUCCESS,
-	    ("vm_map_insert(bio_transient_map) rv %d %jx %lx",
-	    rv, (uintmax_t)addr, size));
-	vm_map_unlock(bio_transient_map);
 	atomic_add_int(&inflight_transient_maps, 1);
 	pmap_qenter((vm_offset_t)addr, bp->bio_ma, OFF_TO_IDX(size));
 	bp->bio_data = (caddr_t)addr + bp->bio_ma_offset;

Added: head/sys/kern/subr_vmem.c
==============================================================================
--- /dev/null	00:00:00 1970	(empty, because file is newly added)
+++ head/sys/kern/subr_vmem.c	Fri Jun 28 03:51:20 2013	(r252330)
@@ -0,0 +1,1372 @@
+/*-
+ * Copyright (c)2006,2007,2008,2009 YAMAMOTO Takashi,
+ * Copyright (c) 2013 EMC Corp.
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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:
+ *	$NetBSD: vmem_impl.h,v 1.2 2013/01/29 21:26:24 para Exp $
+ *	$NetBSD: subr_vmem.c,v 1.83 2013/03/06 11:20:10 yamt Exp $
+ */
+
+/*
+ * reference:
+ * -	Magazines and Vmem: Extending the Slab Allocator
+ *	to Many CPUs and Arbitrary Resources
+ *	http://www.usenix.org/event/usenix01/bonwick.html
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "opt_ddb.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/queue.h>
+#include <sys/callout.h>
+#include <sys/hash.h>
+#include <sys/lock.h>
+#include <sys/malloc.h>
+#include <sys/mutex.h>
+#include <sys/smp.h>
+#include <sys/condvar.h>
+#include <sys/taskqueue.h>
+#include <sys/vmem.h>
+
+#include <vm/uma.h>
+#include <vm/vm.h>
+#include <vm/pmap.h>
+#include <vm/vm_map.h>
+#include <vm/vm_kern.h>
+#include <vm/vm_extern.h>
+#include <vm/vm_param.h>
+#include <vm/vm_pageout.h>
+
+#define	VMEM_MAXORDER		(sizeof(vmem_size_t) * NBBY)
+
+#define	VMEM_HASHSIZE_MIN	16
+#define	VMEM_HASHSIZE_MAX	131072
+
+#define	VMEM_QCACHE_IDX_MAX	16
+
+#define	VMEM_FITMASK	(M_BESTFIT | M_FIRSTFIT)
+
+#define	VMEM_FLAGS						\
+    (M_NOWAIT | M_WAITOK | M_USE_RESERVE | M_NOVM | M_BESTFIT | M_FIRSTFIT)
+
+#define	BT_FLAGS	(M_NOWAIT | M_WAITOK | M_USE_RESERVE | M_NOVM)
+
+#define	QC_NAME_MAX	16
+
+/*
+ * Data structures private to vmem.
+ */
+MALLOC_DEFINE(M_VMEM, "vmem", "vmem internal structures");
+
+typedef struct vmem_btag bt_t;
+
+TAILQ_HEAD(vmem_seglist, vmem_btag);
+LIST_HEAD(vmem_freelist, vmem_btag);
+LIST_HEAD(vmem_hashlist, vmem_btag);
+
+struct qcache {
+	uma_zone_t	qc_cache;
+	vmem_t 		*qc_vmem;
+	vmem_size_t	qc_size;
+	char		qc_name[QC_NAME_MAX];
+};
+typedef struct qcache qcache_t;
+#define	QC_POOL_TO_QCACHE(pool)	((qcache_t *)(pool->pr_qcache))
+
+#define	VMEM_NAME_MAX	16
+
+/* vmem arena */
+struct vmem {
+	struct mtx_padalign	vm_lock;
+	struct cv		vm_cv;
+	char			vm_name[VMEM_NAME_MAX+1];
+	LIST_ENTRY(vmem)	vm_alllist;
+	struct vmem_hashlist	vm_hash0[VMEM_HASHSIZE_MIN];
+	struct vmem_freelist	vm_freelist[VMEM_MAXORDER];
+	struct vmem_seglist	vm_seglist;
+	struct vmem_hashlist	*vm_hashlist;
+	vmem_size_t		vm_hashsize;
+
+	/* Constant after init */
+	vmem_size_t		vm_qcache_max;
+	vmem_size_t		vm_quantum_mask;
+	vmem_size_t		vm_import_quantum;
+	int			vm_quantum_shift;
+
+	/* Written on alloc/free */
+	LIST_HEAD(, vmem_btag)	vm_freetags;
+	int			vm_nfreetags;
+	int			vm_nbusytag;
+	vmem_size_t		vm_inuse;
+	vmem_size_t		vm_size;
+
+	/* Used on import. */
+	vmem_import_t		*vm_importfn;
+	vmem_release_t		*vm_releasefn;
+	void			*vm_arg;
+
+	/* Space exhaustion callback. */
+	vmem_reclaim_t		*vm_reclaimfn;
+
+	/* quantum cache */
+	qcache_t		vm_qcache[VMEM_QCACHE_IDX_MAX];
+};
+
+/* boundary tag */
+struct vmem_btag {
+	TAILQ_ENTRY(vmem_btag) bt_seglist;
+	union {
+		LIST_ENTRY(vmem_btag) u_freelist; /* BT_TYPE_FREE */
+		LIST_ENTRY(vmem_btag) u_hashlist; /* BT_TYPE_BUSY */
+	} bt_u;
+#define	bt_hashlist	bt_u.u_hashlist
+#define	bt_freelist	bt_u.u_freelist
+	vmem_addr_t	bt_start;
+	vmem_size_t	bt_size;
+	int		bt_type;
+};
+
+#define	BT_TYPE_SPAN		1	/* Allocated from importfn */
+#define	BT_TYPE_SPAN_STATIC	2	/* vmem_add() or create. */
+#define	BT_TYPE_FREE		3	/* Available space. */
+#define	BT_TYPE_BUSY		4	/* Used space. */
+#define	BT_ISSPAN_P(bt)	((bt)->bt_type <= BT_TYPE_SPAN_STATIC)
+
+#define	BT_END(bt)	((bt)->bt_start + (bt)->bt_size - 1)
+
+#if defined(DIAGNOSTIC)
+static void vmem_check(vmem_t *);
+#endif
+
+static struct callout	vmem_periodic_ch;
+static int		vmem_periodic_interval;
+static struct task	vmem_periodic_wk;
+
+static struct mtx_padalign vmem_list_lock;
+static LIST_HEAD(, vmem) vmem_list = LIST_HEAD_INITIALIZER(vmem_list);
+
+/* ---- misc */
+#define	VMEM_CONDVAR_INIT(vm, wchan)	cv_init(&vm->vm_cv, wchan)
+#define	VMEM_CONDVAR_DESTROY(vm)	cv_destroy(&vm->vm_cv)
+#define	VMEM_CONDVAR_WAIT(vm)		cv_wait(&vm->vm_cv, &vm->vm_lock)
+#define	VMEM_CONDVAR_BROADCAST(vm)	cv_broadcast(&vm->vm_cv)
+
+
+#define	VMEM_LOCK(vm)		mtx_lock(&vm->vm_lock)
+#define	VMEM_TRYLOCK(vm)	mtx_trylock(&vm->vm_lock)
+#define	VMEM_UNLOCK(vm)		mtx_unlock(&vm->vm_lock)
+#define	VMEM_LOCK_INIT(vm, name) mtx_init(&vm->vm_lock, (name), NULL, MTX_DEF)
+#define	VMEM_LOCK_DESTROY(vm)	mtx_destroy(&vm->vm_lock)
+#define	VMEM_ASSERT_LOCKED(vm)	mtx_assert(&vm->vm_lock, MA_OWNED);
+
+#define	VMEM_ALIGNUP(addr, align)	(-(-(addr) & -(align)))
+
+#define	VMEM_CROSS_P(addr1, addr2, boundary) \
+	((((addr1) ^ (addr2)) & -(boundary)) != 0)
+
+#define	ORDER2SIZE(order)	((vmem_size_t)1 << (order))
+#define	SIZE2ORDER(size)	((int)flsl(size) - 1)
+
+/*
+ * Maximum number of boundary tags that may be required to satisfy an
+ * allocation.  Two may be required to import.  Another two may be
+ * required to clip edges.
+ */
+#define	BT_MAXALLOC	4
+
+/*
+ * Max free limits the number of locally cached boundary tags.  We
+ * just want to avoid hitting the zone allocator for every call.
+ */
+#define BT_MAXFREE	(BT_MAXALLOC * 8)
+
+/* Allocator for boundary tags. */
+static uma_zone_t vmem_bt_zone;
+
+/* boot time arena storage. */
+static struct vmem buffer_arena_storage;
+static struct vmem transient_arena_storage;
+vmem_t *buffer_arena = &buffer_arena_storage;
+vmem_t *transient_arena = &transient_arena_storage;
+
+/*
+ * Fill the vmem's boundary tag cache.  We guarantee that boundary tag
+ * allocation will not fail once bt_fill() passes.  To do so we cache
+ * at least the maximum possible tag allocations in the arena.
+ */
+static int
+bt_fill(vmem_t *vm, int flags)
+{
+	bt_t *bt;
+
+	VMEM_ASSERT_LOCKED(vm);
+
+	/*
+	 * Loop until we meet the reserve.  To minimize the lock shuffle
+	 * and prevent simultaneous fills we first try a NOWAIT regardless
+	 * of the caller's flags.  Specify M_NOVM so we don't recurse while
+	 * holding a vmem lock.
+	 */
+	while (vm->vm_nfreetags < BT_MAXALLOC) {
+		bt = uma_zalloc(vmem_bt_zone,
+		    (flags & M_USE_RESERVE) | M_NOWAIT | M_NOVM);
+		if (bt == NULL) {
+			VMEM_UNLOCK(vm);
+			bt = uma_zalloc(vmem_bt_zone, flags);
+			VMEM_LOCK(vm);
+			if (bt == NULL && (flags & M_NOWAIT) != 0)
+				break;
+		}
+		LIST_INSERT_HEAD(&vm->vm_freetags, bt, bt_freelist);
+		vm->vm_nfreetags++;
+	}
+
+	if (vm->vm_nfreetags < BT_MAXALLOC)
+		return ENOMEM;
+
+	return 0;
+}
+
+/*
+ * Pop a tag off of the freetag stack.
+ */
+static bt_t *
+bt_alloc(vmem_t *vm)
+{
+	bt_t *bt;
+
+	VMEM_ASSERT_LOCKED(vm);
+	bt = LIST_FIRST(&vm->vm_freetags);
+	MPASS(bt != NULL);
+	LIST_REMOVE(bt, bt_freelist);
+	vm->vm_nfreetags--;
+
+	return bt;
+}
+
+/*
+ * Trim the per-vmem free list.  Returns with the lock released to
+ * avoid allocator recursions.
+ */
+static void
+bt_freetrim(vmem_t *vm, int freelimit)
+{
+	LIST_HEAD(, vmem_btag) freetags;
+	bt_t *bt;
+
+	LIST_INIT(&freetags);
+	VMEM_ASSERT_LOCKED(vm);
+	while (vm->vm_nfreetags > freelimit) {
+		bt = LIST_FIRST(&vm->vm_freetags);
+		LIST_REMOVE(bt, bt_freelist);
+		vm->vm_nfreetags--;
+		LIST_INSERT_HEAD(&freetags, bt, bt_freelist);
+	}
+	VMEM_UNLOCK(vm);
+	while ((bt = LIST_FIRST(&freetags)) != NULL) {
+		LIST_REMOVE(bt, bt_freelist);
+		uma_zfree(vmem_bt_zone, bt);
+	}
+}
+
+static inline void
+bt_free(vmem_t *vm, bt_t *bt)
+{
+
+	VMEM_ASSERT_LOCKED(vm);
+	MPASS(LIST_FIRST(&vm->vm_freetags) != bt);
+	LIST_INSERT_HEAD(&vm->vm_freetags, bt, bt_freelist);
+	vm->vm_nfreetags++;
+}
+
+/*
+ * freelist[0] ... [1, 1]
+ * freelist[1] ... [2, 3]
+ * freelist[2] ... [4, 7]
+ * freelist[3] ... [8, 15]
+ *  :
+ * freelist[n] ... [(1 << n), (1 << (n + 1)) - 1]
+ *  :
+ */
+
+static struct vmem_freelist *
+bt_freehead_tofree(vmem_t *vm, vmem_size_t size)
+{
+	const vmem_size_t qsize = size >> vm->vm_quantum_shift;
+	const int idx = SIZE2ORDER(qsize);
+
+	MPASS(size != 0 && qsize != 0);
+	MPASS((size & vm->vm_quantum_mask) == 0);
+	MPASS(idx >= 0);
+	MPASS(idx < VMEM_MAXORDER);
+
+	return &vm->vm_freelist[idx];
+}
+
+/*
+ * bt_freehead_toalloc: return the freelist for the given size and allocation
+ * strategy.
+ *
+ * For M_FIRSTFIT, return the list in which any blocks are large enough
+ * for the requested size.  otherwise, return the list which can have blocks
+ * large enough for the requested size.
+ */
+static struct vmem_freelist *
+bt_freehead_toalloc(vmem_t *vm, vmem_size_t size, int strat)
+{
+	const vmem_size_t qsize = size >> vm->vm_quantum_shift;
+	int idx = SIZE2ORDER(qsize);
+
+	MPASS(size != 0 && qsize != 0);
+	MPASS((size & vm->vm_quantum_mask) == 0);
+
+	if (strat == M_FIRSTFIT && ORDER2SIZE(idx) != qsize) {
+		idx++;
+		/* check too large request? */
+	}
+	MPASS(idx >= 0);
+	MPASS(idx < VMEM_MAXORDER);
+
+	return &vm->vm_freelist[idx];
+}
+
+/* ---- boundary tag hash */
+
+static struct vmem_hashlist *
+bt_hashhead(vmem_t *vm, vmem_addr_t addr)
+{
+	struct vmem_hashlist *list;
+	unsigned int hash;
+
+	hash = hash32_buf(&addr, sizeof(addr), 0);
+	list = &vm->vm_hashlist[hash % vm->vm_hashsize];
+
+	return list;
+}
+
+static bt_t *
+bt_lookupbusy(vmem_t *vm, vmem_addr_t addr)
+{
+	struct vmem_hashlist *list;
+	bt_t *bt;
+
+	VMEM_ASSERT_LOCKED(vm);
+	list = bt_hashhead(vm, addr); 
+	LIST_FOREACH(bt, list, bt_hashlist) {
+		if (bt->bt_start == addr) {
+			break;
+		}
+	}
+
+	return bt;
+}
+
+static void
+bt_rembusy(vmem_t *vm, bt_t *bt)
+{
+
+	VMEM_ASSERT_LOCKED(vm);
+	MPASS(vm->vm_nbusytag > 0);
+	vm->vm_inuse -= bt->bt_size;
+	vm->vm_nbusytag--;
+	LIST_REMOVE(bt, bt_hashlist);
+}
+
+static void
+bt_insbusy(vmem_t *vm, bt_t *bt)
+{
+	struct vmem_hashlist *list;
+
+	VMEM_ASSERT_LOCKED(vm);
+	MPASS(bt->bt_type == BT_TYPE_BUSY);
+
+	list = bt_hashhead(vm, bt->bt_start);
+	LIST_INSERT_HEAD(list, bt, bt_hashlist);
+	vm->vm_nbusytag++;
+	vm->vm_inuse += bt->bt_size;
+}
+
+/* ---- boundary tag list */
+
+static void
+bt_remseg(vmem_t *vm, bt_t *bt)
+{
+
+	TAILQ_REMOVE(&vm->vm_seglist, bt, bt_seglist);
+	bt_free(vm, bt);
+}
+
+static void
+bt_insseg(vmem_t *vm, bt_t *bt, bt_t *prev)
+{
+
+	TAILQ_INSERT_AFTER(&vm->vm_seglist, prev, bt, bt_seglist);
+}
+
+static void
+bt_insseg_tail(vmem_t *vm, bt_t *bt)
+{
+
+	TAILQ_INSERT_TAIL(&vm->vm_seglist, bt, bt_seglist);
+}
+
+static void
+bt_remfree(vmem_t *vm, bt_t *bt)
+{
+
+	MPASS(bt->bt_type == BT_TYPE_FREE);
+
+	LIST_REMOVE(bt, bt_freelist);
+}
+
+static void
+bt_insfree(vmem_t *vm, bt_t *bt)
+{
+	struct vmem_freelist *list;
+
+	list = bt_freehead_tofree(vm, bt->bt_size);
+	LIST_INSERT_HEAD(list, bt, bt_freelist);
+}
+
+/* ---- vmem internal functions */
+
+/*
+ * Import from the arena into the quantum cache in UMA.
+ */
+static int
+qc_import(void *arg, void **store, int cnt, int flags)
+{
+	qcache_t *qc;
+	vmem_addr_t addr;
+	int i;
+
+	qc = arg;
+	flags |= M_BESTFIT;
+	for (i = 0; i < cnt; i++) {
+		if (vmem_xalloc(qc->qc_vmem, qc->qc_size, 0, 0, 0,
+		    VMEM_ADDR_MIN, VMEM_ADDR_MAX, flags, &addr) != 0)
+			break;
+		store[i] = (void *)addr;
+		/* Only guarantee one allocation. */
+		flags &= ~M_WAITOK;
+		flags |= M_NOWAIT;
+	}
+	return i;
+}
+
+/*
+ * Release memory from the UMA cache to the arena.
+ */
+static void
+qc_release(void *arg, void **store, int cnt)
+{
+	qcache_t *qc;
+	int i;
+
+	qc = arg;
+	for (i = 0; i < cnt; i++)
+		vmem_xfree(qc->qc_vmem, (vmem_addr_t)store[i], qc->qc_size);
+}
+
+static void
+qc_init(vmem_t *vm, vmem_size_t qcache_max)
+{
+	qcache_t *qc;
+	vmem_size_t size;
+	int qcache_idx_max;
+	int i;
+
+	MPASS((qcache_max & vm->vm_quantum_mask) == 0);
+	qcache_idx_max = MIN(qcache_max >> vm->vm_quantum_shift,
+	    VMEM_QCACHE_IDX_MAX);
+	vm->vm_qcache_max = qcache_idx_max << vm->vm_quantum_shift;
+	for (i = 0; i < qcache_idx_max; i++) {
+		qc = &vm->vm_qcache[i];
+		size = (i + 1) << vm->vm_quantum_shift;
+		snprintf(qc->qc_name, sizeof(qc->qc_name), "%s-%zu",
+		    vm->vm_name, size);
+		qc->qc_vmem = vm;
+		qc->qc_size = size;
+		qc->qc_cache = uma_zcache_create(qc->qc_name, size,
+		    NULL, NULL, NULL, NULL, qc_import, qc_release, qc,
+		    UMA_ZONE_VM);
+		MPASS(qc->qc_cache);
+	}
+}
+
+static void
+qc_destroy(vmem_t *vm)
+{
+	int qcache_idx_max;
+	int i;
+
+	qcache_idx_max = vm->vm_qcache_max >> vm->vm_quantum_shift;
+	for (i = 0; i < qcache_idx_max; i++)
+		uma_zdestroy(vm->vm_qcache[i].qc_cache);
+}
+
+static void
+qc_drain(vmem_t *vm)
+{
+	int qcache_idx_max;
+	int i;
+
+	qcache_idx_max = vm->vm_qcache_max >> vm->vm_quantum_shift;
+	for (i = 0; i < qcache_idx_max; i++)
+		zone_drain(vm->vm_qcache[i].qc_cache);
+}
+
+void
+vmem_startup(void)
+{
+
+	mtx_init(&vmem_list_lock, "vmem list lock", NULL, MTX_DEF);
+	vmem_bt_zone = uma_zcreate("vmem btag",
+	    sizeof(struct vmem_btag), NULL, NULL, NULL, NULL,
+	    UMA_ALIGN_PTR, UMA_ZONE_VM);
+}
+
+/* ---- rehash */
+
+static int
+vmem_rehash(vmem_t *vm, vmem_size_t newhashsize)
+{
+	bt_t *bt;
+	int i;
+	struct vmem_hashlist *newhashlist;
+	struct vmem_hashlist *oldhashlist;
+	vmem_size_t oldhashsize;
+
+	MPASS(newhashsize > 0);
+
+	newhashlist = malloc(sizeof(struct vmem_hashlist) * newhashsize,
+	    M_VMEM, M_NOWAIT);
+	if (newhashlist == NULL)
+		return ENOMEM;
+	for (i = 0; i < newhashsize; i++) {
+		LIST_INIT(&newhashlist[i]);
+	}
+
+	VMEM_LOCK(vm);
+	oldhashlist = vm->vm_hashlist;
+	oldhashsize = vm->vm_hashsize;
+	vm->vm_hashlist = newhashlist;
+	vm->vm_hashsize = newhashsize;
+	if (oldhashlist == NULL) {
+		VMEM_UNLOCK(vm);
+		return 0;
+	}
+	for (i = 0; i < oldhashsize; i++) {
+		while ((bt = LIST_FIRST(&oldhashlist[i])) != NULL) {
+			bt_rembusy(vm, bt);
+			bt_insbusy(vm, bt);
+		}
+	}
+	VMEM_UNLOCK(vm);
+
+	if (oldhashlist != vm->vm_hash0) {
+		free(oldhashlist, M_VMEM);
+	}
+
+	return 0;
+}
+
+static void
+vmem_periodic_kick(void *dummy)
+{
+
+	taskqueue_enqueue(taskqueue_thread, &vmem_periodic_wk);
+}
+
+static void
+vmem_periodic(void *unused, int pending)
+{
+	vmem_t *vm;
+	vmem_size_t desired;
+	vmem_size_t current;
+
+	mtx_lock(&vmem_list_lock);
+	LIST_FOREACH(vm, &vmem_list, vm_alllist) {
+#ifdef DIAGNOSTIC
+		/* Convenient time to verify vmem state. */
+		VMEM_LOCK(vm);
+		vmem_check(vm);
+		VMEM_UNLOCK(vm);
+#endif
+		desired = 1 << flsl(vm->vm_nbusytag);
+		desired = MIN(MAX(desired, VMEM_HASHSIZE_MIN),
+		    VMEM_HASHSIZE_MAX);
+		current = vm->vm_hashsize;
+
+		/* Grow in powers of two.  Shrink less aggressively. */
+		if (desired >= current * 2 || desired * 4 <= current)
+			vmem_rehash(vm, desired);
+	}
+	mtx_unlock(&vmem_list_lock);
+
+	callout_reset(&vmem_periodic_ch, vmem_periodic_interval,
+	    vmem_periodic_kick, NULL);
+}
+
+static void
+vmem_start_callout(void *unused)
+{
+
+	TASK_INIT(&vmem_periodic_wk, 0, vmem_periodic, NULL);
+	vmem_periodic_interval = hz * 10;
+	callout_init(&vmem_periodic_ch, CALLOUT_MPSAFE);
+	callout_reset(&vmem_periodic_ch, vmem_periodic_interval,
+	    vmem_periodic_kick, NULL);
+}
+SYSINIT(vfs, SI_SUB_CONFIGURE, SI_ORDER_ANY, vmem_start_callout, NULL);
+
+static void
+vmem_add1(vmem_t *vm, vmem_addr_t addr, vmem_size_t size, int flags, int type)
+{
+	bt_t *btspan;
+	bt_t *btfree;
+
+	MPASS(type == BT_TYPE_SPAN || type == BT_TYPE_SPAN_STATIC);
+
+	btspan = bt_alloc(vm);
+	btspan->bt_type = type;
+	btspan->bt_start = addr;
+	btspan->bt_size = size;
+
+	btfree = bt_alloc(vm);
+	btfree->bt_type = BT_TYPE_FREE;
+	btfree->bt_start = addr;
+	btfree->bt_size = size;
+
+	bt_insseg_tail(vm, btspan);
+	bt_insseg(vm, btfree, btspan);
+	bt_insfree(vm, btfree);
+	vm->vm_size += size;
+}
+
+static void
+vmem_destroy1(vmem_t *vm)
+{
+	bt_t *bt;
+
+	/*
+	 * Drain per-cpu quantum caches.
+	 */
+	qc_destroy(vm);
+
+	/*
+	 * The vmem should now only contain empty segments.
+	 */
+	VMEM_LOCK(vm);
+	MPASS(vm->vm_nbusytag == 0);
+
+	while ((bt = TAILQ_FIRST(&vm->vm_seglist)) != NULL)
+		bt_remseg(vm, bt);
+
+	if (vm->vm_hashlist != NULL && vm->vm_hashlist != vm->vm_hash0)
+		free(vm->vm_hashlist, M_VMEM);
+
+	bt_freetrim(vm, 0);
+
+	VMEM_CONDVAR_DESTROY(vm);
+	VMEM_LOCK_DESTROY(vm);
+	free(vm, M_VMEM);
+}
+
+static int
+vmem_import(vmem_t *vm, vmem_size_t size, int flags)
+{
+	vmem_addr_t addr;
+	int error;
+
+	if (vm->vm_importfn == NULL)
+		return EINVAL;
+
+	size = roundup(size, vm->vm_import_quantum);
+
+	/*
+	 * Hide MAXALLOC tags so we're guaranteed to be able to add this
+	 * span and the tag we want to allocate from it.
+	 */
+	MPASS(vm->vm_nfreetags >= BT_MAXALLOC);
+	vm->vm_nfreetags -= BT_MAXALLOC;
+	VMEM_UNLOCK(vm);
+	error = (vm->vm_importfn)(vm->vm_arg, size, flags, &addr);
+	VMEM_LOCK(vm);
+	vm->vm_nfreetags += BT_MAXALLOC;
+	if (error)
+		return ENOMEM;
+
+	vmem_add1(vm, addr, size, flags, BT_TYPE_SPAN);
+
+	return 0;
+}
+
+/*
+ * vmem_fit: check if a bt can satisfy the given restrictions.
+ *
+ * it's a caller's responsibility to ensure the region is big enough
+ * before calling us.
+ */
+static int
+vmem_fit(const bt_t *bt, vmem_size_t size, vmem_size_t align,
+    vmem_size_t phase, vmem_size_t nocross, vmem_addr_t minaddr,
+    vmem_addr_t maxaddr, vmem_addr_t *addrp)
+{
+	vmem_addr_t start;
+	vmem_addr_t end;
+
+	MPASS(size > 0);
+	MPASS(bt->bt_size >= size); /* caller's responsibility */
+
+	/*
+	 * XXX assumption: vmem_addr_t and vmem_size_t are
+	 * unsigned integer of the same size.
+	 */
+
+	start = bt->bt_start;
+	if (start < minaddr) {
+		start = minaddr;
+	}
+	end = BT_END(bt);
+	if (end > maxaddr)
+		end = maxaddr;
+	if (start > end) 
+		return (ENOMEM);
+
+	start = VMEM_ALIGNUP(start - phase, align) + phase;
+	if (start < bt->bt_start)
+		start += align;
+	if (VMEM_CROSS_P(start, start + size - 1, nocross)) {
+		MPASS(align < nocross);
+		start = VMEM_ALIGNUP(start - phase, nocross) + phase;
+	}
+	if (start <= end && end - start >= size - 1) {
+		MPASS((start & (align - 1)) == phase);
+		MPASS(!VMEM_CROSS_P(start, start + size - 1, nocross));
+		MPASS(minaddr <= start);
+		MPASS(maxaddr == 0 || start + size - 1 <= maxaddr);
+		MPASS(bt->bt_start <= start);
+		MPASS(BT_END(bt) - start >= size - 1);
+		*addrp = start;
+
+		return (0);
+	}
+	return (ENOMEM);
+}
+
+/*
+ * vmem_clip:  Trim the boundary tag edges to the requested start and size.
+ */
+static void
+vmem_clip(vmem_t *vm, bt_t *bt, vmem_addr_t start, vmem_size_t size)
+{
+	bt_t *btnew;
+	bt_t *btprev;
+
+	VMEM_ASSERT_LOCKED(vm);
+	MPASS(bt->bt_type == BT_TYPE_FREE);
+	MPASS(bt->bt_size >= size);
+	bt_remfree(vm, bt);
+	if (bt->bt_start != start) {
+		btprev = bt_alloc(vm);
+		btprev->bt_type = BT_TYPE_FREE;
+		btprev->bt_start = bt->bt_start;
+		btprev->bt_size = start - bt->bt_start;
+		bt->bt_start = start;
+		bt->bt_size -= btprev->bt_size;
+		bt_insfree(vm, btprev);
+		bt_insseg(vm, btprev,
+		    TAILQ_PREV(bt, vmem_seglist, bt_seglist));
+	}
+	MPASS(bt->bt_start == start);
+	if (bt->bt_size != size && bt->bt_size - size > vm->vm_quantum_mask) {
+		/* split */
+		btnew = bt_alloc(vm);
+		btnew->bt_type = BT_TYPE_BUSY;
+		btnew->bt_start = bt->bt_start;
+		btnew->bt_size = size;
+		bt->bt_start = bt->bt_start + size;
+		bt->bt_size -= size;
+		bt_insfree(vm, bt);
+		bt_insseg(vm, btnew,
+		    TAILQ_PREV(bt, vmem_seglist, bt_seglist));
+		bt_insbusy(vm, btnew);
+		bt = btnew;
+	} else {
+		bt->bt_type = BT_TYPE_BUSY;
+		bt_insbusy(vm, bt);
+	}
+	MPASS(bt->bt_size >= size);
+	bt->bt_type = BT_TYPE_BUSY;
+}
+
+/* ---- vmem API */
+
+void
+vmem_set_import(vmem_t *vm, vmem_import_t *importfn,
+     vmem_release_t *releasefn, void *arg, vmem_size_t import_quantum)
+{
+
+	VMEM_LOCK(vm);
+	vm->vm_importfn = importfn;
+	vm->vm_releasefn = releasefn;
+	vm->vm_arg = arg;
+	vm->vm_import_quantum = import_quantum;
+	VMEM_UNLOCK(vm);
+}
+
+void
+vmem_set_reclaim(vmem_t *vm, vmem_reclaim_t *reclaimfn)
+{
+
+	VMEM_LOCK(vm);
+	vm->vm_reclaimfn = reclaimfn;
+	VMEM_UNLOCK(vm);
+}
+
+/*
+ * vmem_init: Initializes vmem arena.
+ */
+vmem_t *
+vmem_init(vmem_t *vm, const char *name, vmem_addr_t base, vmem_size_t size,
+    vmem_size_t quantum, vmem_size_t qcache_max, int flags)
+{
+	int i;
+
+	MPASS(quantum > 0);
+
+	bzero(vm, sizeof(*vm));
+
+	VMEM_CONDVAR_INIT(vm, name);
+	VMEM_LOCK_INIT(vm, name);
+	vm->vm_nfreetags = 0;
+	LIST_INIT(&vm->vm_freetags);
+	strlcpy(vm->vm_name, name, sizeof(vm->vm_name));
+	vm->vm_quantum_mask = quantum - 1;
+	vm->vm_quantum_shift = SIZE2ORDER(quantum);
+	MPASS(ORDER2SIZE(vm->vm_quantum_shift) == quantum);
+	vm->vm_nbusytag = 0;
+	vm->vm_size = 0;
+	vm->vm_inuse = 0;
+	qc_init(vm, qcache_max);
+
+	TAILQ_INIT(&vm->vm_seglist);
+	for (i = 0; i < VMEM_MAXORDER; i++) {
+		LIST_INIT(&vm->vm_freelist[i]);
+	}
+	memset(&vm->vm_hash0, 0, sizeof(vm->vm_hash0));
+	vm->vm_hashsize = VMEM_HASHSIZE_MIN;
+	vm->vm_hashlist = vm->vm_hash0;
+
+	if (size != 0) {
+		if (vmem_add(vm, base, size, flags) != 0) {
+			vmem_destroy1(vm);
+			return NULL;
+		}
+	}
+
+	mtx_lock(&vmem_list_lock);
+	LIST_INSERT_HEAD(&vmem_list, vm, vm_alllist);
+	mtx_unlock(&vmem_list_lock);
+
+	return vm;
+}
+
+/*
+ * vmem_create: create an arena.
+ */
+vmem_t *
+vmem_create(const char *name, vmem_addr_t base, vmem_size_t size,
+    vmem_size_t quantum, vmem_size_t qcache_max, int flags)
+{
+
+	vmem_t *vm;
+
+	vm = malloc(sizeof(*vm), M_VMEM, flags & (M_WAITOK|M_NOWAIT));
+	if (vm == NULL)
+		return (NULL);
+	if (vmem_init(vm, name, base, size, quantum, qcache_max,
+	    flags) == NULL) {
+		free(vm, M_VMEM);
+		return (NULL);
+	}
+	return (vm);
+}
+
+void
+vmem_destroy(vmem_t *vm)
+{
+
+	mtx_lock(&vmem_list_lock);
+	LIST_REMOVE(vm, vm_alllist);
+	mtx_unlock(&vmem_list_lock);
+
+	vmem_destroy1(vm);
+}

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