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vmem.c
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vmem.c
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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2008 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/* #pragma ident "@(#)vmem.c 1.10 05/06/08 SMI" */
/*
* For a more complete description of the main ideas, see:
*
* Jeff Bonwick and Jonathan Adams,
*
* Magazines and vmem: Extending the Slab Allocator to Many CPUs and
* Arbitrary Resources.
*
* Proceedings of the 2001 Usenix Conference.
* Available as /shared/sac/PSARC/2000/550/materials/vmem.pdf.
*
* For the "Big Theory Statement", see usr/src/uts/common/os/vmem.c
*
* 1. Overview of changes
* ------------------------------
* There have been a few changes to vmem in order to support umem. The
* main areas are:
*
* * VM_SLEEP unsupported
*
* * Reaping changes
*
* * initialization changes
*
* * _vmem_extend_alloc
*
*
* 2. VM_SLEEP Removed
* -------------------
* Since VM_SLEEP allocations can hold locks (in vmem_populate()) for
* possibly infinite amounts of time, they are not supported in this
* version of vmem. Sleep-like behavior can be achieved through
* UMEM_NOFAIL umem allocations.
*
*
* 3. Reaping changes
* ------------------
* Unlike kmem_reap(), which just asynchronously schedules work, umem_reap()
* can do allocations and frees synchronously. This is a problem if it
* occurs during a vmem_populate() allocation.
*
* Instead, we delay reaps while populates are active.
*
*
* 4. Initialization changes
* -------------------------
* In the kernel, vmem_init() allows you to create a single, top-level arena,
* which has vmem_internal_arena as a child. For umem, we want to be able
* to extend arenas dynamically. It is much easier to support this if we
* allow a two-level "heap" arena:
*
* +----------+
* | "fake" |
* +----------+
* |
* +----------+
* | "heap" |
* +----------+
* | \ \
* | +-+-- ... <other children>
* |
* +---------------+
* | vmem_internal |
* +---------------+
* | | | |
* <children>
*
* The new vmem_init() allows you to specify a "parent" of the heap, along
* with allocation functions.
*
*
* 5. _vmem_extend_alloc
* ---------------------
* The other part of extending is _vmem_extend_alloc. This function allows
* you to extend (expand current spans, if possible) an arena and allocate
* a chunk of the newly extened span atomically. This is needed to support
* extending the heap while vmem_populate()ing it.
*
* In order to increase the usefulness of extending, non-imported spans are
* sorted in address order.
*/
#include "config.h"
/* #include "mtlib.h" */
#include <sys/vmem_impl_user.h>
#if HAVE_ALLOCA_H
#include <alloca.h>
#endif
#ifdef HAVE_SYS_SYSMACROS_H
#include <sys/sysmacros.h>
#endif
#include <stdio.h>
#if HAVE_STRINGS_H
#include <strings.h>
#endif
#if HAVE_ATOMIC_H
#include <atomic.h>
#endif
#include "vmem_base.h"
#include "umem_base.h"
#define VMEM_INITIAL 6 /* early vmem arenas */
#define VMEM_SEG_INITIAL 100 /* early segments */
/*
* Adding a new span to an arena requires two segment structures: one to
* represent the span, and one to represent the free segment it contains.
*/
#define VMEM_SEGS_PER_SPAN_CREATE 2
/*
* Allocating a piece of an existing segment requires 0-2 segment structures
* depending on how much of the segment we're allocating.
*
* To allocate the entire segment, no new segment structures are needed; we
* simply move the existing segment structure from the freelist to the
* allocation hash table.
*
* To allocate a piece from the left or right end of the segment, we must
* split the segment into two pieces (allocated part and remainder), so we
* need one new segment structure to represent the remainder.
*
* To allocate from the middle of a segment, we need two new segment strucures
* to represent the remainders on either side of the allocated part.
*/
#define VMEM_SEGS_PER_EXACT_ALLOC 0
#define VMEM_SEGS_PER_LEFT_ALLOC 1
#define VMEM_SEGS_PER_RIGHT_ALLOC 1
#define VMEM_SEGS_PER_MIDDLE_ALLOC 2
/*
* vmem_populate() preallocates segment structures for vmem to do its work.
* It must preallocate enough for the worst case, which is when we must import
* a new span and then allocate from the middle of it.
*/
#define VMEM_SEGS_PER_ALLOC_MAX \
(VMEM_SEGS_PER_SPAN_CREATE + VMEM_SEGS_PER_MIDDLE_ALLOC)
/*
* The segment structures themselves are allocated from vmem_seg_arena, so
* we have a recursion problem when vmem_seg_arena needs to populate itself.
* We address this by working out the maximum number of segment structures
* this act will require, and multiplying by the maximum number of threads
* that we'll allow to do it simultaneously.
*
* The worst-case segment consumption to populate vmem_seg_arena is as
* follows (depicted as a stack trace to indicate why events are occurring):
*
* vmem_alloc(vmem_seg_arena) -> 2 segs (span create + exact alloc)
* vmem_alloc(vmem_internal_arena) -> 2 segs (span create + exact alloc)
* heap_alloc(heap_arena)
* vmem_alloc(heap_arena) -> 4 seg (span create + alloc)
* parent_alloc(parent_arena)
* _vmem_extend_alloc(parent_arena) -> 3 seg (span create + left alloc)
*
* Note: The reservation for heap_arena must be 4, since vmem_xalloc()
* is overly pessimistic on allocations where parent_arena has a stricter
* alignment than heap_arena.
*
* The worst-case consumption for any arena is 4 segment structures.
* For now, we only support VM_NOSLEEP allocations, so as long as we
* serialize all vmem_populates, a 4-seg reserve is sufficient.
*/
#define VMEM_POPULATE_SEGS_PER_ARENA 4
#define VMEM_POPULATE_LOCKS 1
#define VMEM_POPULATE_RESERVE \
(VMEM_POPULATE_SEGS_PER_ARENA * VMEM_POPULATE_LOCKS)
/*
* vmem_populate() ensures that each arena has VMEM_MINFREE seg structures
* so that it can satisfy the worst-case allocation *and* participate in
* worst-case allocation from vmem_seg_arena.
*/
#define VMEM_MINFREE (VMEM_POPULATE_RESERVE + VMEM_SEGS_PER_ALLOC_MAX)
/* Don't assume new statics are zeroed - see vmem_startup() */
static vmem_t vmem0[VMEM_INITIAL];
static vmem_t *vmem_populator[VMEM_INITIAL];
static uint32_t vmem_id;
static uint32_t vmem_populators;
static vmem_seg_t vmem_seg0[VMEM_SEG_INITIAL];
static vmem_seg_t *vmem_segfree;
static mutex_t vmem_list_lock = DEFAULTMUTEX;
static mutex_t vmem_segfree_lock = DEFAULTMUTEX;
static vmem_populate_lock_t vmem_nosleep_lock = {
DEFAULTMUTEX,
0
};
#define IN_POPULATE() (vmem_nosleep_lock.vmpl_thr == thr_self())
static vmem_t *vmem_list;
static vmem_t *vmem_internal_arena;
static vmem_t *vmem_seg_arena;
static vmem_t *vmem_hash_arena;
static vmem_t *vmem_vmem_arena;
vmem_t *vmem_heap;
vmem_alloc_t *vmem_heap_alloc;
vmem_free_t *vmem_heap_free;
uint32_t vmem_mtbf; /* mean time between failures [default: off] */
size_t vmem_seg_size = sizeof (vmem_seg_t);
/*
* Insert/delete from arena list (type 'a') or next-of-kin list (type 'k').
*/
#define VMEM_INSERT(vprev, vsp, type) \
{ \
vmem_seg_t *vnext = (vprev)->vs_##type##next; \
(vsp)->vs_##type##next = (vnext); \
(vsp)->vs_##type##prev = (vprev); \
(vprev)->vs_##type##next = (vsp); \
(vnext)->vs_##type##prev = (vsp); \
}
#define VMEM_DELETE(vsp, type) \
{ \
vmem_seg_t *vprev = (vsp)->vs_##type##prev; \
vmem_seg_t *vnext = (vsp)->vs_##type##next; \
(vprev)->vs_##type##next = (vnext); \
(vnext)->vs_##type##prev = (vprev); \
}
/*
* Get a vmem_seg_t from the global segfree list.
*/
static vmem_seg_t *
vmem_getseg_global(void)
{
vmem_seg_t *vsp;
(void) mutex_lock(&vmem_segfree_lock);
if ((vsp = vmem_segfree) != NULL)
vmem_segfree = vsp->vs_knext;
(void) mutex_unlock(&vmem_segfree_lock);
return (vsp);
}
/*
* Put a vmem_seg_t on the global segfree list.
*/
static void
vmem_putseg_global(vmem_seg_t *vsp)
{
(void) mutex_lock(&vmem_segfree_lock);
vsp->vs_knext = vmem_segfree;
vmem_segfree = vsp;
(void) mutex_unlock(&vmem_segfree_lock);
}
/*
* Get a vmem_seg_t from vmp's segfree list.
*/
static vmem_seg_t *
vmem_getseg(vmem_t *vmp)
{
vmem_seg_t *vsp;
ASSERT(vmp->vm_nsegfree > 0);
vsp = vmp->vm_segfree;
vmp->vm_segfree = vsp->vs_knext;
vmp->vm_nsegfree--;
return (vsp);
}
/*
* Put a vmem_seg_t on vmp's segfree list.
*/
static void
vmem_putseg(vmem_t *vmp, vmem_seg_t *vsp)
{
vsp->vs_knext = vmp->vm_segfree;
vmp->vm_segfree = vsp;
vmp->vm_nsegfree++;
}
/*
* Add vsp to the appropriate freelist.
*/
static void
vmem_freelist_insert(vmem_t *vmp, vmem_seg_t *vsp)
{
vmem_seg_t *vprev;
ASSERT(*VMEM_HASH(vmp, vsp->vs_start) != vsp);
vprev = (vmem_seg_t *)&vmp->vm_freelist[highbit(VS_SIZE(vsp)) - 1];
vsp->vs_type = VMEM_FREE;
vmp->vm_freemap |= VS_SIZE(vprev);
VMEM_INSERT(vprev, vsp, k);
(void) cond_broadcast(&vmp->vm_cv);
}
/*
* Take vsp from the freelist.
*/
static void
vmem_freelist_delete(vmem_t *vmp, vmem_seg_t *vsp)
{
ASSERT(*VMEM_HASH(vmp, vsp->vs_start) != vsp);
ASSERT(vsp->vs_type == VMEM_FREE);
if (vsp->vs_knext->vs_start == 0 && vsp->vs_kprev->vs_start == 0) {
/*
* The segments on both sides of 'vsp' are freelist heads,
* so taking vsp leaves the freelist at vsp->vs_kprev empty.
*/
ASSERT(vmp->vm_freemap & VS_SIZE(vsp->vs_kprev));
vmp->vm_freemap ^= VS_SIZE(vsp->vs_kprev);
}
VMEM_DELETE(vsp, k);
}
/*
* Add vsp to the allocated-segment hash table and update kstats.
*/
static void
vmem_hash_insert(vmem_t *vmp, vmem_seg_t *vsp)
{
vmem_seg_t **bucket;
vsp->vs_type = VMEM_ALLOC;
bucket = VMEM_HASH(vmp, vsp->vs_start);
vsp->vs_knext = *bucket;
*bucket = vsp;
if (vmem_seg_size == sizeof (vmem_seg_t)) {
vsp->vs_depth = (uint8_t)getpcstack(vsp->vs_stack,
VMEM_STACK_DEPTH, 0);
vsp->vs_thread = thr_self();
vsp->vs_timestamp = gethrtime();
} else {
vsp->vs_depth = 0;
}
vmp->vm_kstat.vk_alloc++;
vmp->vm_kstat.vk_mem_inuse += VS_SIZE(vsp);
}
/*
* Remove vsp from the allocated-segment hash table and update kstats.
*/
static vmem_seg_t *
vmem_hash_delete(vmem_t *vmp, uintptr_t addr, size_t size)
{
vmem_seg_t *vsp, **prev_vspp;
prev_vspp = VMEM_HASH(vmp, addr);
while ((vsp = *prev_vspp) != NULL) {
if (vsp->vs_start == addr) {
*prev_vspp = vsp->vs_knext;
break;
}
vmp->vm_kstat.vk_lookup++;
prev_vspp = &vsp->vs_knext;
}
if (vsp == NULL) {
umem_panic("vmem_hash_delete(%p, %lx, %lu): bad free",
vmp, addr, size);
}
if (VS_SIZE(vsp) != size) {
umem_panic("vmem_hash_delete(%p, %lx, %lu): wrong size "
"(expect %lu)", vmp, addr, size, VS_SIZE(vsp));
}
vmp->vm_kstat.vk_free++;
vmp->vm_kstat.vk_mem_inuse -= size;
return (vsp);
}
/*
* Create a segment spanning the range [start, end) and add it to the arena.
*/
static vmem_seg_t *
vmem_seg_create(vmem_t *vmp, vmem_seg_t *vprev, uintptr_t start, uintptr_t end)
{
vmem_seg_t *newseg = vmem_getseg(vmp);
newseg->vs_start = start;
newseg->vs_end = end;
newseg->vs_type = 0;
newseg->vs_import = 0;
VMEM_INSERT(vprev, newseg, a);
return (newseg);
}
/*
* Remove segment vsp from the arena.
*/
static void
vmem_seg_destroy(vmem_t *vmp, vmem_seg_t *vsp)
{
ASSERT(vsp->vs_type != VMEM_ROTOR);
VMEM_DELETE(vsp, a);
vmem_putseg(vmp, vsp);
}
/*
* Add the span [vaddr, vaddr + size) to vmp and update kstats.
*/
static vmem_seg_t *
vmem_span_create(vmem_t *vmp, void *vaddr, size_t size, uint8_t import)
{
vmem_seg_t *knext;
vmem_seg_t *newseg, *span;
uintptr_t start = (uintptr_t)vaddr;
uintptr_t end = start + size;
knext = &vmp->vm_seg0;
if (!import && vmp->vm_source_alloc == NULL) {
vmem_seg_t *kend, *kprev;
/*
* non-imported spans are sorted in address order. This
* makes vmem_extend_unlocked() much more effective.
*
* We search in reverse order, since new spans are
* generally at higher addresses.
*/
kend = &vmp->vm_seg0;
for (kprev = kend->vs_kprev; kprev != kend;
kprev = kprev->vs_kprev) {
if (!kprev->vs_import && (kprev->vs_end - 1) < start)
break;
}
knext = kprev->vs_knext;
}
ASSERT(MUTEX_HELD(&vmp->vm_lock));
if ((start | end) & (vmp->vm_quantum - 1)) {
umem_panic("vmem_span_create(%p, %p, %lu): misaligned",
vmp, vaddr, size);
}
span = vmem_seg_create(vmp, knext->vs_aprev, start, end);
span->vs_type = VMEM_SPAN;
VMEM_INSERT(knext->vs_kprev, span, k);
newseg = vmem_seg_create(vmp, span, start, end);
vmem_freelist_insert(vmp, newseg);
newseg->vs_import = import;
if (import)
vmp->vm_kstat.vk_mem_import += size;
vmp->vm_kstat.vk_mem_total += size;
return (newseg);
}
/*
* Remove span vsp from vmp and update kstats.
*/
static void
vmem_span_destroy(vmem_t *vmp, vmem_seg_t *vsp)
{
vmem_seg_t *span = vsp->vs_aprev;
size_t size = VS_SIZE(vsp);
ASSERT(MUTEX_HELD(&vmp->vm_lock));
ASSERT(span->vs_type == VMEM_SPAN);
if (vsp->vs_import)
vmp->vm_kstat.vk_mem_import -= size;
vmp->vm_kstat.vk_mem_total -= size;
VMEM_DELETE(span, k);
vmem_seg_destroy(vmp, vsp);
vmem_seg_destroy(vmp, span);
}
/*
* Allocate the subrange [addr, addr + size) from segment vsp.
* If there are leftovers on either side, place them on the freelist.
* Returns a pointer to the segment representing [addr, addr + size).
*/
static vmem_seg_t *
vmem_seg_alloc(vmem_t *vmp, vmem_seg_t *vsp, uintptr_t addr, size_t size)
{
uintptr_t vs_start = vsp->vs_start;
uintptr_t vs_end = vsp->vs_end;
size_t vs_size = vs_end - vs_start;
size_t realsize = P2ROUNDUP(size, vmp->vm_quantum);
uintptr_t addr_end = addr + realsize;
ASSERT(P2PHASE(vs_start, vmp->vm_quantum) == 0);
ASSERT(P2PHASE(addr, vmp->vm_quantum) == 0);
ASSERT(vsp->vs_type == VMEM_FREE);
ASSERT(addr >= vs_start && addr_end - 1 <= vs_end - 1);
ASSERT(addr - 1 <= addr_end - 1);
/*
* If we're allocating from the start of the segment, and the
* remainder will be on the same freelist, we can save quite
* a bit of work.
*/
if (P2SAMEHIGHBIT(vs_size, vs_size - realsize) && addr == vs_start) {
ASSERT(highbit(vs_size) == highbit(vs_size - realsize));
vsp->vs_start = addr_end;
vsp = vmem_seg_create(vmp, vsp->vs_aprev, addr, addr + size);
vmem_hash_insert(vmp, vsp);
return (vsp);
}
vmem_freelist_delete(vmp, vsp);
if (vs_end != addr_end)
vmem_freelist_insert(vmp,
vmem_seg_create(vmp, vsp, addr_end, vs_end));
if (vs_start != addr)
vmem_freelist_insert(vmp,
vmem_seg_create(vmp, vsp->vs_aprev, vs_start, addr));
vsp->vs_start = addr;
vsp->vs_end = addr + size;
vmem_hash_insert(vmp, vsp);
return (vsp);
}
/*
* We cannot reap if we are in the middle of a vmem_populate().
*/
void
vmem_reap(void)
{
if (!IN_POPULATE())
umem_reap();
}
/*
* Populate vmp's segfree list with VMEM_MINFREE vmem_seg_t structures.
*/
static int
vmem_populate(vmem_t *vmp, int vmflag)
{
char *p;
vmem_seg_t *vsp;
ssize_t nseg;
size_t size;
vmem_populate_lock_t *lp;
int i;
while (vmp->vm_nsegfree < VMEM_MINFREE &&
(vsp = vmem_getseg_global()) != NULL)
vmem_putseg(vmp, vsp);
if (vmp->vm_nsegfree >= VMEM_MINFREE)
return (1);
/*
* If we're already populating, tap the reserve.
*/
if (vmem_nosleep_lock.vmpl_thr == thr_self()) {
ASSERT(vmp->vm_cflags & VMC_POPULATOR);
return (1);
}
(void) mutex_unlock(&vmp->vm_lock);
ASSERT(vmflag & VM_NOSLEEP); /* we do not allow sleep allocations */
lp = &vmem_nosleep_lock;
/*
* Cannot be just a mutex_lock(), since that has no effect if
* libthread is not linked.
*/
(void) mutex_lock(&lp->vmpl_mutex);
ASSERT(lp->vmpl_thr == 0);
lp->vmpl_thr = thr_self();
nseg = VMEM_MINFREE + vmem_populators * VMEM_POPULATE_RESERVE;
size = P2ROUNDUP(nseg * vmem_seg_size, vmem_seg_arena->vm_quantum);
nseg = size / vmem_seg_size;
/*
* The following vmem_alloc() may need to populate vmem_seg_arena
* and all the things it imports from. When doing so, it will tap
* each arena's reserve to prevent recursion (see the block comment
* above the definition of VMEM_POPULATE_RESERVE).
*
* During this allocation, vmem_reap() is a no-op. If the allocation
* fails, we call vmem_reap() after dropping the population lock.
*/
p = vmem_alloc(vmem_seg_arena, size, vmflag & VM_UMFLAGS);
if (p == NULL) {
lp->vmpl_thr = 0;
(void) mutex_unlock(&lp->vmpl_mutex);
vmem_reap();
(void) mutex_lock(&vmp->vm_lock);
vmp->vm_kstat.vk_populate_fail++;
return (0);
}
/*
* Restock the arenas that may have been depleted during population.
*/
for (i = 0; i < vmem_populators; i++) {
(void) mutex_lock(&vmem_populator[i]->vm_lock);
while (vmem_populator[i]->vm_nsegfree < VMEM_POPULATE_RESERVE)
vmem_putseg(vmem_populator[i],
(vmem_seg_t *)(p + --nseg * vmem_seg_size));
(void) mutex_unlock(&vmem_populator[i]->vm_lock);
}
lp->vmpl_thr = 0;
(void) mutex_unlock(&lp->vmpl_mutex);
(void) mutex_lock(&vmp->vm_lock);
/*
* Now take our own segments.
*/
ASSERT(nseg >= VMEM_MINFREE);
while (vmp->vm_nsegfree < VMEM_MINFREE)
vmem_putseg(vmp, (vmem_seg_t *)(p + --nseg * vmem_seg_size));
/*
* Give the remainder to charity.
*/
while (nseg > 0)
vmem_putseg_global((vmem_seg_t *)(p + --nseg * vmem_seg_size));
return (1);
}
/*
* Advance a walker from its previous position to 'afterme'.
* Note: may drop and reacquire vmp->vm_lock.
*/
static void
vmem_advance(vmem_t *vmp, vmem_seg_t *walker, vmem_seg_t *afterme)
{
vmem_seg_t *vprev = walker->vs_aprev;
vmem_seg_t *vnext = walker->vs_anext;
vmem_seg_t *vsp = NULL;
VMEM_DELETE(walker, a);
if (afterme != NULL)
VMEM_INSERT(afterme, walker, a);
/*
* The walker segment's presence may have prevented its neighbors
* from coalescing. If so, coalesce them now.
*/
if (vprev->vs_type == VMEM_FREE) {
if (vnext->vs_type == VMEM_FREE) {
ASSERT(vprev->vs_end == vnext->vs_start);
vmem_freelist_delete(vmp, vnext);
vmem_freelist_delete(vmp, vprev);
vprev->vs_end = vnext->vs_end;
vmem_freelist_insert(vmp, vprev);
vmem_seg_destroy(vmp, vnext);
}
vsp = vprev;
} else if (vnext->vs_type == VMEM_FREE) {
vsp = vnext;
}
/*
* vsp could represent a complete imported span,
* in which case we must return it to the source.
*/
if (vsp != NULL && vsp->vs_import && vmp->vm_source_free != NULL &&
vsp->vs_aprev->vs_type == VMEM_SPAN &&
vsp->vs_anext->vs_type == VMEM_SPAN) {
void *vaddr = (void *)vsp->vs_start;
size_t size = VS_SIZE(vsp);
ASSERT(size == VS_SIZE(vsp->vs_aprev));
vmem_freelist_delete(vmp, vsp);
vmem_span_destroy(vmp, vsp);
(void) mutex_unlock(&vmp->vm_lock);
vmp->vm_source_free(vmp->vm_source, vaddr, size);
(void) mutex_lock(&vmp->vm_lock);
}
}
/*
* VM_NEXTFIT allocations deliberately cycle through all virtual addresses
* in an arena, so that we avoid reusing addresses for as long as possible.
* This helps to catch used-after-freed bugs. It's also the perfect policy
* for allocating things like process IDs, where we want to cycle through
* all values in order.
*/
static void *
vmem_nextfit_alloc(vmem_t *vmp, size_t size, int vmflag)
{
vmem_seg_t *vsp, *rotor;
uintptr_t addr;
size_t realsize = P2ROUNDUP(size, vmp->vm_quantum);
size_t vs_size;
(void) mutex_lock(&vmp->vm_lock);
if (vmp->vm_nsegfree < VMEM_MINFREE && !vmem_populate(vmp, vmflag)) {
(void) mutex_unlock(&vmp->vm_lock);
return (NULL);
}
/*
* The common case is that the segment right after the rotor is free,
* and large enough that extracting 'size' bytes won't change which
* freelist it's on. In this case we can avoid a *lot* of work.
* Instead of the normal vmem_seg_alloc(), we just advance the start
* address of the victim segment. Instead of moving the rotor, we
* create the new segment structure *behind the rotor*, which has
* the same effect. And finally, we know we don't have to coalesce
* the rotor's neighbors because the new segment lies between them.
*/
rotor = &vmp->vm_rotor;
vsp = rotor->vs_anext;
if (vsp->vs_type == VMEM_FREE && (vs_size = VS_SIZE(vsp)) > realsize &&
P2SAMEHIGHBIT(vs_size, vs_size - realsize)) {
ASSERT(highbit(vs_size) == highbit(vs_size - realsize));
addr = vsp->vs_start;
vsp->vs_start = addr + realsize;
vmem_hash_insert(vmp,
vmem_seg_create(vmp, rotor->vs_aprev, addr, addr + size));
(void) mutex_unlock(&vmp->vm_lock);
return ((void *)addr);
}
/*
* Starting at the rotor, look for a segment large enough to
* satisfy the allocation.
*/
for (;;) {
vmp->vm_kstat.vk_search++;
if (vsp->vs_type == VMEM_FREE && VS_SIZE(vsp) >= size)
break;
vsp = vsp->vs_anext;
if (vsp == rotor) {
int cancel_state;
/*
* We've come full circle. One possibility is that the
* there's actually enough space, but the rotor itself
* is preventing the allocation from succeeding because
* it's sitting between two free segments. Therefore,
* we advance the rotor and see if that liberates a
* suitable segment.
*/
vmem_advance(vmp, rotor, rotor->vs_anext);
vsp = rotor->vs_aprev;
if (vsp->vs_type == VMEM_FREE && VS_SIZE(vsp) >= size)
break;
/*
* If there's a lower arena we can import from, or it's
* a VM_NOSLEEP allocation, let vmem_xalloc() handle it.
* Otherwise, wait until another thread frees something.
*/
if (vmp->vm_source_alloc != NULL ||
(vmflag & VM_NOSLEEP)) {
(void) mutex_unlock(&vmp->vm_lock);
return (vmem_xalloc(vmp, size, vmp->vm_quantum,
0, 0, NULL, NULL, vmflag & VM_UMFLAGS));
}
vmp->vm_kstat.vk_wait++;
(void) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE,
&cancel_state);
(void) cond_wait(&vmp->vm_cv, &vmp->vm_lock);
(void) pthread_setcancelstate(cancel_state, NULL);
vsp = rotor->vs_anext;
}
}
/*
* We found a segment. Extract enough space to satisfy the allocation.
*/
addr = vsp->vs_start;
vsp = vmem_seg_alloc(vmp, vsp, addr, size);
ASSERT(vsp->vs_type == VMEM_ALLOC &&
vsp->vs_start == addr && vsp->vs_end == addr + size);
/*
* Advance the rotor to right after the newly-allocated segment.
* That's where the next VM_NEXTFIT allocation will begin searching.
*/
vmem_advance(vmp, rotor, vsp);
(void) mutex_unlock(&vmp->vm_lock);
return ((void *)addr);
}
/*
* Allocate size bytes at offset phase from an align boundary such that the
* resulting segment [addr, addr + size) is a subset of [minaddr, maxaddr)
* that does not straddle a nocross-aligned boundary.
*/
void *
vmem_xalloc(vmem_t *vmp, size_t size, size_t align, size_t phase,
size_t nocross, void *minaddr, void *maxaddr, int vmflag)
{
vmem_seg_t *vsp;
vmem_seg_t *vbest = NULL;
uintptr_t addr, taddr, start, end;
void *vaddr;
int hb, flist, resv;
uint32_t mtbf;
if (phase > 0 && phase >= align)
umem_panic("vmem_xalloc(%p, %lu, %lu, %lu, %lu, %p, %p, %x): "
"invalid phase",
(void *)vmp, size, align, phase, nocross,
minaddr, maxaddr, vmflag);
if (align == 0)
align = vmp->vm_quantum;
if ((align | phase | nocross) & (vmp->vm_quantum - 1)) {
umem_panic("vmem_xalloc(%p, %lu, %lu, %lu, %lu, %p, %p, %x): "
"parameters not vm_quantum aligned",
(void *)vmp, size, align, phase, nocross,
minaddr, maxaddr, vmflag);
}
if (nocross != 0 &&
(align > nocross || P2ROUNDUP(phase + size, align) > nocross)) {
umem_panic("vmem_xalloc(%p, %lu, %lu, %lu, %lu, %p, %p, %x): "
"overconstrained allocation",
(void *)vmp, size, align, phase, nocross,
minaddr, maxaddr, vmflag);
}
if ((mtbf = vmem_mtbf | vmp->vm_mtbf) != 0 && gethrtime() % mtbf == 0 &&
(vmflag & (VM_NOSLEEP | VM_PANIC)) == VM_NOSLEEP)
return (NULL);
(void) mutex_lock(&vmp->vm_lock);
for (;;) {
int cancel_state;
if (vmp->vm_nsegfree < VMEM_MINFREE &&
!vmem_populate(vmp, vmflag))
break;
/*
* highbit() returns the highest bit + 1, which is exactly
* what we want: we want to search the first freelist whose
* members are *definitely* large enough to satisfy our
* allocation. However, there are certain cases in which we
* want to look at the next-smallest freelist (which *might*
* be able to satisfy the allocation):
*
* (1) The size is exactly a power of 2, in which case
* the smaller freelist is always big enough;
*
* (2) All other freelists are empty;
*
* (3) We're in the highest possible freelist, which is
* always empty (e.g. the 4GB freelist on 32-bit systems);
*
* (4) We're doing a best-fit or first-fit allocation.
*/
if ((size & (size - 1)) == 0) {
flist = lowbit(P2ALIGN(vmp->vm_freemap, size));
} else {
hb = highbit(size);
if ((vmp->vm_freemap >> hb) == 0 ||
hb == VMEM_FREELISTS ||
(vmflag & (VM_BESTFIT | VM_FIRSTFIT)))
hb--;
flist = lowbit(P2ALIGN(vmp->vm_freemap, 1UL << hb));
}
for (vbest = NULL, vsp = (flist == 0) ? NULL :
vmp->vm_freelist[flist - 1].vs_knext;
vsp != NULL; vsp = vsp->vs_knext) {
vmp->vm_kstat.vk_search++;
if (vsp->vs_start == 0) {
/*
* We're moving up to a larger freelist,
* so if we've already found a candidate,
* the fit can't possibly get any better.
*/
if (vbest != NULL)
break;
/*
* Find the next non-empty freelist.
*/
flist = lowbit(P2ALIGN(vmp->vm_freemap,
VS_SIZE(vsp)));
if (flist-- == 0)
break;
vsp = (vmem_seg_t *)&vmp->vm_freelist[flist];
ASSERT(vsp->vs_knext->vs_type == VMEM_FREE);
continue;
}
if (vsp->vs_end - 1 < (uintptr_t)minaddr)
continue;
if (vsp->vs_start > (uintptr_t)maxaddr - 1)
continue;
start = MAX(vsp->vs_start, (uintptr_t)minaddr);
end = MIN(vsp->vs_end - 1, (uintptr_t)maxaddr - 1) + 1;
taddr = P2PHASEUP(start, align, phase);
if (P2BOUNDARY(taddr, size, nocross))
taddr +=
P2ROUNDUP(P2NPHASE(taddr, nocross), align);
if ((taddr - start) + size > end - start ||
(vbest != NULL && VS_SIZE(vsp) >= VS_SIZE(vbest)))
continue;
vbest = vsp;
addr = taddr;
if (!(vmflag & VM_BESTFIT) || VS_SIZE(vbest) == size)
break;
}
if (vbest != NULL)
break;
if (size == 0)
umem_panic("vmem_xalloc(): size == 0");
if (vmp->vm_source_alloc != NULL && nocross == 0 &&
minaddr == NULL && maxaddr == NULL) {
size_t asize = P2ROUNDUP(size + phase,
MAX(align, vmp->vm_source->vm_quantum));
if (asize < size) { /* overflow */
(void) mutex_unlock(&vmp->vm_lock);
if (vmflag & VM_NOSLEEP)
return (NULL);
umem_panic("vmem_xalloc(): "
"overflow on VM_SLEEP allocation");
}
/*
* Determine how many segment structures we'll consume.
* The calculation must be presise because if we're
* here on behalf of vmem_populate(), we are taking
* segments from a very limited reserve.
*/
resv = (size == asize) ?
VMEM_SEGS_PER_SPAN_CREATE +
VMEM_SEGS_PER_EXACT_ALLOC :
VMEM_SEGS_PER_ALLOC_MAX;
ASSERT(vmp->vm_nsegfree >= resv);
vmp->vm_nsegfree -= resv; /* reserve our segs */
(void) mutex_unlock(&vmp->vm_lock);
vaddr = vmp->vm_source_alloc(vmp->vm_source, asize,
vmflag & VM_UMFLAGS);
(void) mutex_lock(&vmp->vm_lock);
vmp->vm_nsegfree += resv; /* claim reservation */
if (vaddr != NULL) {
vbest = vmem_span_create(vmp, vaddr, asize, 1);
addr = P2PHASEUP(vbest->vs_start, align, phase);
break;
}
}
(void) mutex_unlock(&vmp->vm_lock);
vmem_reap();
(void) mutex_lock(&vmp->vm_lock);
if (vmflag & VM_NOSLEEP)
break;
vmp->vm_kstat.vk_wait++;
(void) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE,
&cancel_state);
(void) cond_wait(&vmp->vm_cv, &vmp->vm_lock);
(void) pthread_setcancelstate(cancel_state, NULL);
}
if (vbest != NULL) {
ASSERT(vbest->vs_type == VMEM_FREE);
ASSERT(vbest->vs_knext != vbest);
(void) vmem_seg_alloc(vmp, vbest, addr, size);
(void) mutex_unlock(&vmp->vm_lock);
ASSERT(P2PHASE(addr, align) == phase);
ASSERT(!P2BOUNDARY(addr, size, nocross));