dmake: do not set MAKEFLAGS=k

[unleashed/tickless.git] / kernel / vm / seg_kmem.c

/*
 * 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 (c) 1998, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2016 Joyent, Inc.
 */

#include <sys/types.h>
#include <sys/t_lock.h>
#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/tuneable.h>
#include <sys/systm.h>
#include <sys/vm.h>
#include <sys/kmem.h>
#include <sys/vmem.h>
#include <sys/mman.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/dumphdr.h>
#include <sys/bootconf.h>
#include <sys/lgrp.h>
#include <vm/seg_kmem.h>
#include <vm/hat.h>
#include <vm/page.h>
#include <vm/vm_dep.h>
#include <vm/faultcode.h>
#include <sys/promif.h>
#include <vm/seg_kp.h>
#include <sys/bitmap.h>
#include <sys/mem_cage.h>


/*
 * seg_kmem is the primary kernel memory segment driver.  It
 * maps the kernel heap [kernelheap, ekernelheap), module text,
 * and all memory which was allocated before the VM was initialized
 * into kas.
 *
 * Pages which belong to seg_kmem are hashed into &kvp vnode at
 * an offset equal to (uoff_t)virt_addr, and have p_lckcnt >= 1.
 * They must never be paged out since segkmem_fault() is a no-op to
 * prevent recursive faults.
 *
 * Currently, seg_kmem pages are sharelocked (p_sharelock == 1) on
 * __x86 and are unlocked (p_sharelock == 0) on __sparc.  Once __x86
 * supports relocation the #ifdef kludges can be removed.
 *
 * seg_kmem pages may be subject to relocation by page_relocate(),
 * provided that the HAT supports it; if this is so, segkmem_reloc
 * will be set to a nonzero value. All boot time allocated memory as
 * well as static memory is considered off limits to relocation.
 * Pages are "relocatable" if p_state does not have P_NORELOC set, so
 * we request P_NORELOC pages for memory that isn't safe to relocate.
 *
 * The kernel heap is logically divided up into four pieces:
 *
 *   heap32_arena is for allocations that require 32-bit absolute
 *   virtual addresses (e.g. code that uses 32-bit pointers/offsets).
 *
 *   heap_core is for allocations that require 2GB *relative*
 *   offsets; in other words all memory from heap_core is within
 *   2GB of all other memory from the same arena. This is a requirement
 *   of the addressing modes of some processors in supervisor code.
 *
 *   heap_arena is the general heap arena.
 *
 *   static_arena is the static memory arena.  Allocations from it
 *   are not subject to relocation so it is safe to use the memory
 *   physical address as well as the virtual address (e.g. the VA to
 *   PA translations are static).  Caches may import from static_arena;
 *   all other static memory allocations should use static_alloc_arena.
 *
 * On some platforms which have limited virtual address space, seg_kmem
 * may share [kernelheap, ekernelheap) with seg_kp; if this is so,
 * segkp_bitmap is non-NULL, and each bit represents a page of virtual
 * address space which is actually seg_kp mapped.
 */

extern ulong_t *segkp_bitmap;   /* Is set if segkp is from the kernel heap */

char *kernelheap;               /* start of primary kernel heap */
char *ekernelheap;              /* end of primary kernel heap */
struct seg kvseg;               /* primary kernel heap segment */
struct seg kvseg_core;          /* "core" kernel heap segment */
struct seg kzioseg;             /* Segment for zio mappings */
vmem_t *heap_arena;             /* primary kernel heap arena */
vmem_t *heap_core_arena;        /* core kernel heap arena */
char *heap_core_base;           /* start of core kernel heap arena */
char *heap_lp_base;             /* start of kernel large page heap arena */
char *heap_lp_end;              /* end of kernel large page heap arena */
vmem_t *hat_memload_arena;      /* HAT translation data */
struct seg kvseg32;             /* 32-bit kernel heap segment */
vmem_t *heap32_arena;           /* 32-bit kernel heap arena */
vmem_t *heaptext_arena;         /* heaptext arena */
struct as kas;                  /* kernel address space */
int segkmem_reloc;              /* enable/disable relocatable segkmem pages */
vmem_t *static_arena;           /* arena for caches to import static memory */
vmem_t *static_alloc_arena;     /* arena for allocating static memory */
vmem_t *zio_arena = NULL;       /* arena for allocating zio memory */
vmem_t *zio_alloc_arena = NULL; /* arena for allocating zio memory */

/*
 * seg_kmem driver can map part of the kernel heap with large pages.
 * Currently this functionality is implemented for sparc platforms only.
 *
 * The large page size "segkmem_lpsize" for kernel heap is selected in the
 * platform specific code. It can also be modified via /etc/system file.
 * Setting segkmem_lpsize to PAGESIZE in /etc/system disables usage of large
 * pages for kernel heap. "segkmem_lpshift" is adjusted appropriately to
 * match segkmem_lpsize.
 *
 * At boot time we carve from kernel heap arena a range of virtual addresses
 * that will be used for large page mappings. This range [heap_lp_base,
 * heap_lp_end) is set up as a separate vmem arena - "heap_lp_arena". We also
 * create "kmem_lp_arena" that caches memory already backed up by large
 * pages. kmem_lp_arena imports virtual segments from heap_lp_arena.
 */

size_t  segkmem_lpsize;
static  uint_t  segkmem_lpshift = PAGESHIFT;
int     segkmem_lpszc = 0;

size_t  segkmem_kmemlp_quantum = 0x400000;      /* 4MB */
size_t  segkmem_heaplp_quantum;
vmem_t *heap_lp_arena;
static  vmem_t *kmem_lp_arena;
static  vmem_t *segkmem_ppa_arena;
static  segkmem_lpcb_t segkmem_lpcb;

/*
 * We use "segkmem_kmemlp_max" to limit the total amount of physical memory
 * consumed by the large page heap. By default this parameter is set to 1/8 of
 * physmem but can be adjusted through /etc/system either directly or
 * indirectly by setting "segkmem_kmemlp_pcnt" to the percent of physmem
 * we allow for large page heap.
 */
size_t  segkmem_kmemlp_max;
static  uint_t  segkmem_kmemlp_pcnt;

/*
 * Getting large pages for kernel heap could be problematic due to
 * physical memory fragmentation. That's why we allow to preallocate
 * "segkmem_kmemlp_min" bytes at boot time.
 */
static  size_t  segkmem_kmemlp_min;

/*
 * Throttling is used to avoid expensive tries to allocate large pages
 * for kernel heap when a lot of succesive attempts to do so fail.
 */
static  ulong_t segkmem_lpthrottle_max = 0x400000;
static  ulong_t segkmem_lpthrottle_start = 0x40;
static  ulong_t segkmem_use_lpthrottle = 1;

/*
 * Freed pages accumulate on a garbage list until segkmem is ready,
 * at which point we call segkmem_gc() to free it all.
 */
typedef struct segkmem_gc_list {
        struct segkmem_gc_list  *gc_next;
        vmem_t                  *gc_arena;
        size_t                  gc_size;
} segkmem_gc_list_t;

static segkmem_gc_list_t *segkmem_gc_list;

/*
 * Allocations from the hat_memload arena add VM_MEMLOAD to their
 * vmflags so that segkmem_xalloc() can inform the hat layer that it needs
 * to take steps to prevent infinite recursion.  HAT allocations also
 * must be non-relocatable to prevent recursive page faults.
 */
static void *
hat_memload_alloc(vmem_t *vmp, size_t size, int flags)
{
        flags |= (VM_MEMLOAD | VM_NORELOC);
        return (segkmem_alloc(vmp, size, flags));
}

/*
 * Allocations from static_arena arena (or any other arena that uses
 * segkmem_alloc_permanent()) require non-relocatable (permanently
 * wired) memory pages, since these pages are referenced by physical
 * as well as virtual address.
 */
void *
segkmem_alloc_permanent(vmem_t *vmp, size_t size, int flags)
{
        return (segkmem_alloc(vmp, size, flags | VM_NORELOC));
}

/*
 * Initialize kernel heap boundaries.
 */
void
kernelheap_init(
        void *heap_start,
        void *heap_end,
        char *first_avail,
        void *core_start,
        void *core_end)
{
        uintptr_t textbase;
        size_t core_size;
        size_t heap_size;
        vmem_t *heaptext_parent;
        size_t  heap_lp_size = 0;

        kernelheap = heap_start;
        ekernelheap = heap_end;


        /*
         * If this platform has a 'core' heap area, then the space for
         * overflow module text should be carved out of the end of that
         * heap.  Otherwise, it gets carved out of the general purpose
         * heap.
         */
        core_size = (uintptr_t)core_end - (uintptr_t)core_start;
        if (core_size > 0) {
                ASSERT(core_size >= HEAPTEXT_SIZE);
                textbase = (uintptr_t)core_end - HEAPTEXT_SIZE;
                core_size -= HEAPTEXT_SIZE;
        }
        else {
                ekernelheap -= HEAPTEXT_SIZE;
                textbase = (uintptr_t)ekernelheap;
        }

        heap_size = (uintptr_t)ekernelheap - (uintptr_t)kernelheap;
        heap_arena = vmem_init("heap", kernelheap, heap_size, PAGESIZE,
            segkmem_alloc, segkmem_free);

        if (core_size > 0) {
                heap_core_arena = vmem_create("heap_core", core_start,
                    core_size, PAGESIZE, NULL, NULL, NULL, 0, VM_SLEEP);
                heap_core_base = core_start;
        } else {
                heap_core_arena = heap_arena;
                heap_core_base = kernelheap;
        }

        /*
         * reserve space for the large page heap. If large pages for kernel
         * heap is enabled large page heap arean will be created later in the
         * boot sequence in segkmem_heap_lp_init(). Otherwise the allocated
         * range will be returned back to the heap_arena.
         */
        if (heap_lp_size) {
                (void) vmem_xalloc(heap_arena, heap_lp_size, PAGESIZE, 0, 0,
                    heap_lp_base, heap_lp_end,
                    VM_NOSLEEP | VM_BESTFIT | VM_PANIC);
        }

        /*
         * Remove the already-spoken-for memory range [kernelheap, first_avail).
         */
        (void) vmem_xalloc(heap_arena, first_avail - kernelheap, PAGESIZE,
            0, 0, kernelheap, first_avail, VM_NOSLEEP | VM_BESTFIT | VM_PANIC);

        heap32_arena = heap_core_arena;
        heaptext_parent = heap_core_arena;

        heaptext_arena = vmem_create("heaptext", (void *)textbase,
            HEAPTEXT_SIZE, PAGESIZE, NULL, NULL, heaptext_parent, 0, VM_SLEEP);

        /*
         * Create a set of arenas for memory with static translations
         * (e.g. VA -> PA translations cannot change).  Since using
         * kernel pages by physical address implies it isn't safe to
         * walk across page boundaries, the static_arena quantum must
         * be PAGESIZE.  Any kmem caches that require static memory
         * should source from static_arena, while direct allocations
         * should only use static_alloc_arena.
         */
        static_arena = vmem_create("static", NULL, 0, PAGESIZE,
            segkmem_alloc_permanent, segkmem_free, heap_arena, 0, VM_SLEEP);
        static_alloc_arena = vmem_create("static_alloc", NULL, 0,
            sizeof (uint64_t), vmem_alloc, vmem_free, static_arena,
            0, VM_SLEEP);

        /*
         * Create an arena for translation data (ptes, hmes, or hblks).
         * We need an arena for this because hat_memload() is essential
         * to vmem_populate() (see comments in kernel/os/vmem.c).
         *
         * Note: any kmem cache that allocates from hat_memload_arena
         * must be created as a KMC_NOHASH cache (i.e. no external slab
         * and bufctl structures to allocate) so that slab creation doesn't
         * require anything more than a single vmem_alloc().
         */
        hat_memload_arena = vmem_create("hat_memload", NULL, 0, PAGESIZE,
            hat_memload_alloc, segkmem_free, heap_arena, 0,
            VM_SLEEP | VMC_POPULATOR | VMC_DUMPSAFE);
}

void
boot_mapin(caddr_t addr, size_t size)
{
        caddr_t  eaddr;
        page_t  *pp;
        pfn_t    pfnum;

        if (page_resv(btop(size), KM_NOSLEEP) == 0)
                panic("boot_mapin: page_resv failed");

        for (eaddr = addr + size; addr < eaddr; addr += PAGESIZE) {
                pfnum = va_to_pfn(addr);
                if (pfnum == PFN_INVALID)
                        continue;
                if ((pp = page_numtopp_nolock(pfnum)) == NULL)
                        panic("boot_mapin(): No pp for pfnum = %lx", pfnum);

                /*
                 * must break up any large pages that may have constituent
                 * pages being utilized for BOP_ALLOC()'s before calling
                 * page_numtopp().The locking code (ie. page_reclaim())
                 * can't handle them
                 */
                if (pp->p_szc != 0)
                        page_boot_demote(pp);

                pp = page_numtopp(pfnum, SE_EXCL);
                if (pp == NULL || PP_ISFREE(pp))
                        panic("boot_alloc: pp is NULL or free");

                /*
                 * If the cage is on but doesn't yet contain this page,
                 * mark it as non-relocatable.
                 */
                if (kcage_on && !PP_ISNORELOC(pp)) {
                        PP_SETNORELOC(pp);
                        PLCNT_XFER_NORELOC(pp);
                }

                (void) page_hashin(pp, &kvp.v_object, (uoff_t)(uintptr_t)addr,
                                   false);
                pp->p_lckcnt = 1;
#if defined(__x86)
                page_downgrade(pp);
#else
                page_unlock(pp);
#endif
        }
}

/*
 * Get pages from boot and hash them into the kernel's vp.
 * Used after page structs have been allocated, but before segkmem is ready.
 */
void *
boot_alloc(void *inaddr, size_t size, uint_t align)
{
        caddr_t addr = inaddr;

        if (bootops == NULL)
                prom_panic("boot_alloc: attempt to allocate memory after "
                    "BOP_GONE");

        size = ptob(btopr(size));
        if (BOP_ALLOC(bootops, addr, size, align) != addr)
                panic("boot_alloc: BOP_ALLOC failed");
        boot_mapin((caddr_t)addr, size);
        return (addr);
}

static void
segkmem_badop()
{
        panic("segkmem_badop");
}

#define SEGKMEM_BADOP(t)        (t(*)())segkmem_badop

/*ARGSUSED*/
static faultcode_t
segkmem_fault(struct hat *hat, struct seg *seg, caddr_t addr, size_t size,
        enum fault_type type, enum seg_rw rw)
{
        pgcnt_t npages;
        spgcnt_t pg;
        page_t *pp;
        struct vnode *vp = seg->s_data;

        ASSERT(RW_READ_HELD(&seg->s_as->a_lock));

        if (seg->s_as != &kas || size > seg->s_size ||
            addr < seg->s_base || addr + size > seg->s_base + seg->s_size)
                panic("segkmem_fault: bad args");

        /*
         * If it is one of segkp pages, call segkp_fault.
         */
        if (segkp_bitmap && seg == &kvseg &&
            BT_TEST(segkp_bitmap, btop((uintptr_t)(addr - seg->s_base))))
                return (segop_fault(hat, segkp, addr, size, type, rw));

        if (rw != S_READ && rw != S_WRITE && rw != S_OTHER)
                return (FC_NOSUPPORT);

        npages = btopr(size);

        switch (type) {
        case F_SOFTLOCK:        /* lock down already-loaded translations */
                for (pg = 0; pg < npages; pg++) {
                        pp = page_lookup(&vp->v_object, (uoff_t)(uintptr_t)addr,
                            SE_SHARED);
                        if (pp == NULL) {
                                /*
                                 * Hmm, no page. Does a kernel mapping
                                 * exist for it?
                                 */
                                if (!hat_probe(kas.a_hat, addr)) {
                                        addr -= PAGESIZE;
                                        while (--pg >= 0) {
                                                pp = page_find(&vp->v_object,
                                                    (uoff_t)(uintptr_t)addr);
                                                if (pp)
                                                        page_unlock(pp);
                                                addr -= PAGESIZE;
                                        }
                                        return (FC_NOMAP);
                                }
                        }
                        addr += PAGESIZE;
                }
                if (rw == S_OTHER)
                        hat_reserve(seg->s_as, addr, size);
                return (0);
        case F_SOFTUNLOCK:
                while (npages--) {
                        pp = page_find(&vp->v_object, (uoff_t)(uintptr_t)addr);
                        if (pp)
                                page_unlock(pp);
                        addr += PAGESIZE;
                }
                return (0);
        default:
                return (FC_NOSUPPORT);
        }
        /*NOTREACHED*/
}

static int
segkmem_setprot(struct seg *seg, caddr_t addr, size_t size, uint_t prot)
{
        ASSERT(RW_LOCK_HELD(&seg->s_as->a_lock));

        if (seg->s_as != &kas || size > seg->s_size ||
            addr < seg->s_base || addr + size > seg->s_base + seg->s_size)
                panic("segkmem_setprot: bad args");

        /*
         * If it is one of segkp pages, call segkp.
         */
        if (segkp_bitmap && seg == &kvseg &&
            BT_TEST(segkp_bitmap, btop((uintptr_t)(addr - seg->s_base))))
                return (segop_setprot(segkp, addr, size, prot));

        if (prot == 0)
                hat_unload(kas.a_hat, addr, size, HAT_UNLOAD);
        else
                hat_chgprot(kas.a_hat, addr, size, prot);
        return (0);
}

/*
 * This is a dummy segkmem function overloaded to call segkp
 * when segkp is under the heap.
 */
/* ARGSUSED */
static int
segkmem_checkprot(struct seg *seg, caddr_t addr, size_t size, uint_t prot)
{
        ASSERT(RW_LOCK_HELD(&seg->s_as->a_lock));

        if (seg->s_as != &kas)
                segkmem_badop();

        /*
         * If it is one of segkp pages, call into segkp.
         */
        if (segkp_bitmap && seg == &kvseg &&
            BT_TEST(segkp_bitmap, btop((uintptr_t)(addr - seg->s_base))))
                return (segop_checkprot(segkp, addr, size, prot));

        segkmem_badop();
        return (0);
}

/*
 * This is a dummy segkmem function overloaded to call segkp
 * when segkp is under the heap.
 */
/* ARGSUSED */
static int
segkmem_kluster(struct seg *seg, caddr_t addr, ssize_t delta)
{
        ASSERT(RW_LOCK_HELD(&seg->s_as->a_lock));

        if (seg->s_as != &kas)
                segkmem_badop();

        /*
         * If it is one of segkp pages, call into segkp.
         */
        if (segkp_bitmap && seg == &kvseg &&
            BT_TEST(segkp_bitmap, btop((uintptr_t)(addr - seg->s_base))))
                return (segop_kluster(segkp, addr, delta));

        segkmem_badop();
        return (0);
}

static void
segkmem_xdump_range(void *arg, void *start, size_t size)
{
        struct as *as = arg;
        caddr_t addr = start;
        caddr_t addr_end = addr + size;

        while (addr < addr_end) {
                pfn_t pfn = hat_getpfnum(kas.a_hat, addr);
                if (pfn != PFN_INVALID && pfn <= physmax && pf_is_memory(pfn))
                        dump_addpage(as, addr, pfn);
                addr += PAGESIZE;
                dump_timeleft = dump_timeout;
        }
}

static void
segkmem_dump_range(void *arg, void *start, size_t size)
{
        caddr_t addr = start;
        caddr_t addr_end = addr + size;

        /*
         * If we are about to start dumping the range of addresses we
         * carved out of the kernel heap for the large page heap walk
         * heap_lp_arena to find what segments are actually populated
         */
        if (SEGKMEM_USE_LARGEPAGES &&
            addr == heap_lp_base && addr_end == heap_lp_end &&
            vmem_size(heap_lp_arena, VMEM_ALLOC) < size) {
                vmem_walk(heap_lp_arena, VMEM_ALLOC | VMEM_REENTRANT,
                    segkmem_xdump_range, arg);
        } else {
                segkmem_xdump_range(arg, start, size);
        }
}

static void
segkmem_dump(struct seg *seg)
{
        /*
         * The kernel's heap_arena (represented by kvseg) is a very large
         * VA space, most of which is typically unused.  To speed up dumping
         * we use vmem_walk() to quickly find the pieces of heap_arena that
         * are actually in use.  We do the same for heap32_arena and
         * heap_core.
         *
         * We specify VMEM_REENTRANT to vmem_walk() because dump_addpage()
         * may ultimately need to allocate memory.  Reentrant walks are
         * necessarily imperfect snapshots.  The kernel heap continues
         * to change during a live crash dump, for example.  For a normal
         * crash dump, however, we know that there won't be any other threads
         * messing with the heap.  Therefore, at worst, we may fail to dump
         * the pages that get allocated by the act of dumping; but we will
         * always dump every page that was allocated when the walk began.
         *
         * The other segkmem segments are dense (fully populated), so there's
         * no need to use this technique when dumping them.
         *
         * Note: when adding special dump handling for any new sparsely-
         * populated segments, be sure to add similar handling to the ::kgrep
         * code in mdb.
         */
        if (seg == &kvseg) {
                vmem_walk(heap_arena, VMEM_ALLOC | VMEM_REENTRANT,
                    segkmem_dump_range, seg->s_as);
                vmem_walk(heaptext_arena, VMEM_ALLOC | VMEM_REENTRANT,
                    segkmem_dump_range, seg->s_as);
        } else if (seg == &kvseg_core) {
                vmem_walk(heap_core_arena, VMEM_ALLOC | VMEM_REENTRANT,
                    segkmem_dump_range, seg->s_as);
        } else if (seg == &kvseg32) {
                vmem_walk(heap32_arena, VMEM_ALLOC | VMEM_REENTRANT,
                    segkmem_dump_range, seg->s_as);
                vmem_walk(heaptext_arena, VMEM_ALLOC | VMEM_REENTRANT,
                    segkmem_dump_range, seg->s_as);
        } else if (seg == &kzioseg) {
                /*
                 * We don't want to dump pages attached to kzioseg since they
                 * contain file data from ZFS.  If this page's segment is
                 * kzioseg return instead of writing it to the dump device.
                 */
                return;
        } else {
                segkmem_dump_range(seg->s_as, seg->s_base, seg->s_size);
        }
}

/*
 * lock/unlock kmem pages over a given range [addr, addr+len).
 * Returns a shadow list of pages in ppp. If there are holes
 * in the range (e.g. some of the kernel mappings do not have
 * underlying page_ts) returns ENOTSUP so that as_pagelock()
 * will handle the range via as_fault(F_SOFTLOCK).
 */
/*ARGSUSED*/
static int
segkmem_pagelock(struct seg *seg, caddr_t addr, size_t len,
        page_t ***ppp, enum lock_type type, enum seg_rw rw)
{
        page_t **pplist, *pp;
        pgcnt_t npages;
        spgcnt_t pg;
        size_t nb;
        struct vnode *vp = seg->s_data;

        ASSERT(ppp != NULL);

        /*
         * If it is one of segkp pages, call into segkp.
         */
        if (segkp_bitmap && seg == &kvseg &&
            BT_TEST(segkp_bitmap, btop((uintptr_t)(addr - seg->s_base))))
                return (segop_pagelock(segkp, addr, len, ppp, type, rw));

        npages = btopr(len);
        nb = sizeof (page_t *) * npages;

        if (type == L_PAGEUNLOCK) {
                pplist = *ppp;
                ASSERT(pplist != NULL);

                for (pg = 0; pg < npages; pg++) {
                        pp = pplist[pg];
                        page_unlock(pp);
                }
                kmem_free(pplist, nb);
                return (0);
        }

        ASSERT(type == L_PAGELOCK);

        pplist = kmem_alloc(nb, KM_NOSLEEP);
        if (pplist == NULL) {
                *ppp = NULL;
                return (ENOTSUP);       /* take the slow path */
        }

        for (pg = 0; pg < npages; pg++) {
                pp = page_lookup(&vp->v_object, (uoff_t)(uintptr_t)addr,
                                 SE_SHARED);
                if (pp == NULL) {
                        while (--pg >= 0)
                                page_unlock(pplist[pg]);
                        kmem_free(pplist, nb);
                        *ppp = NULL;
                        return (ENOTSUP);
                }
                pplist[pg] = pp;
                addr += PAGESIZE;
        }

        *ppp = pplist;
        return (0);
}

/*
 * This is a dummy segkmem function overloaded to call segkp
 * when segkp is under the heap.
 */
/* ARGSUSED */
static int
segkmem_getmemid(struct seg *seg, caddr_t addr, memid_t *memidp)
{
        ASSERT(RW_LOCK_HELD(&seg->s_as->a_lock));

        if (seg->s_as != &kas)
                segkmem_badop();

        /*
         * If it is one of segkp pages, call into segkp.
         */
        if (segkp_bitmap && seg == &kvseg &&
            BT_TEST(segkp_bitmap, btop((uintptr_t)(addr - seg->s_base))))
                return (segop_getmemid(segkp, addr, memidp));

        segkmem_badop();
        return (0);
}

/*ARGSUSED*/
static int
segkmem_capable(struct seg *seg, segcapability_t capability)
{
        if (capability == S_CAPABILITY_NOMINFLT)
                return (1);
        return (0);
}

const struct seg_ops segkmem_ops = {
        .dup            = SEGKMEM_BADOP(int),
        .unmap          = SEGKMEM_BADOP(int),
        .free           = SEGKMEM_BADOP(void),
        .fault          = segkmem_fault,
        .faulta         = SEGKMEM_BADOP(faultcode_t),
        .setprot        = segkmem_setprot,
        .checkprot      = segkmem_checkprot,
        .kluster        = segkmem_kluster,
        .sync           = SEGKMEM_BADOP(int),
        .incore         = SEGKMEM_BADOP(size_t),
        .lockop         = SEGKMEM_BADOP(int),
        .getprot        = SEGKMEM_BADOP(int),
        .getoffset      = SEGKMEM_BADOP(uoff_t),
        .gettype        = SEGKMEM_BADOP(int),
        .getvp          = SEGKMEM_BADOP(int),
        .advise         = SEGKMEM_BADOP(int),
        .dump           = segkmem_dump,
        .pagelock       = segkmem_pagelock,
        .setpagesize    = SEGKMEM_BADOP(int),
        .getmemid       = segkmem_getmemid,
        .capable        = segkmem_capable,
};

int
segkmem_zio_create(struct seg *seg)
{
        ASSERT(seg->s_as == &kas && RW_WRITE_HELD(&kas.a_lock));
        seg->s_ops = &segkmem_ops;
        seg->s_data = &zvp;
        kas.a_size += seg->s_size;
        return (0);
}

int
segkmem_create(struct seg *seg)
{
        ASSERT(seg->s_as == &kas && RW_WRITE_HELD(&kas.a_lock));
        seg->s_ops = &segkmem_ops;
        seg->s_data = &kvp;
        kas.a_size += seg->s_size;
        return (0);
}

/*ARGSUSED*/
page_t *
segkmem_page_create(void *addr, size_t size, int vmflag, void *arg)
{
        struct seg kseg;
        int pgflags;
        struct vnode *vp = arg;

        if (vp == NULL)
                vp = &kvp;

        kseg.s_as = &kas;
        pgflags = PG_EXCL;

        if (segkmem_reloc == 0 || (vmflag & VM_NORELOC))
                pgflags |= PG_NORELOC;
        if ((vmflag & VM_NOSLEEP) == 0)
                pgflags |= PG_WAIT;
        if (vmflag & VM_PANIC)
                pgflags |= PG_PANIC;
        if (vmflag & VM_PUSHPAGE)
                pgflags |= PG_PUSHPAGE;
        if (vmflag & VM_NORMALPRI) {
                ASSERT(vmflag & VM_NOSLEEP);
                pgflags |= PG_NORMALPRI;
        }

        return (page_create_va(&vp->v_object, (uoff_t)(uintptr_t)addr, size,
            pgflags, &kseg, addr));
}

/*
 * Allocate pages to back the virtual address range [addr, addr + size).
 * If addr is NULL, allocate the virtual address space as well.
 */
void *
segkmem_xalloc(vmem_t *vmp, void *inaddr, size_t size, int vmflag, uint_t attr,
        page_t *(*page_create_func)(void *, size_t, int, void *), void *pcarg)
{
        page_t *ppl;
        caddr_t addr = inaddr;
        pgcnt_t npages = btopr(size);
        int allocflag;

        if (inaddr == NULL && (addr = vmem_alloc(vmp, size, vmflag)) == NULL)
                return (NULL);

        ASSERT(((uintptr_t)addr & PAGEOFFSET) == 0);

        if (page_resv(npages, vmflag & VM_KMFLAGS) == 0) {
                if (inaddr == NULL)
                        vmem_free(vmp, addr, size);
                return (NULL);
        }

        ppl = page_create_func(addr, size, vmflag, pcarg);
        if (ppl == NULL) {
                if (inaddr == NULL)
                        vmem_free(vmp, addr, size);
                page_unresv(npages);
                return (NULL);
        }

        /*
         * Under certain conditions, we need to let the HAT layer know
         * that it cannot safely allocate memory.  Allocations from
         * the hat_memload vmem arena always need this, to prevent
         * infinite recursion.
         *
         * In addition, the x86 hat cannot safely do memory
         * allocations while in vmem_populate(), because there
         * is no simple bound on its usage.
         */
        if (vmflag & VM_MEMLOAD)
                allocflag = HAT_NO_KALLOC;
#if defined(__x86)
        else if (vmem_is_populator())
                allocflag = HAT_NO_KALLOC;
#endif
        else
                allocflag = 0;

        while (ppl != NULL) {
                page_t *pp = ppl;
                page_sub(&ppl, pp);
                ASSERT(page_iolock_assert(pp));
                ASSERT(PAGE_EXCL(pp));
                page_io_unlock(pp);
                hat_memload(kas.a_hat, (caddr_t)(uintptr_t)pp->p_offset, pp,
                    (PROT_ALL & ~PROT_USER) | HAT_NOSYNC | attr,
                    HAT_LOAD_LOCK | allocflag);
                pp->p_lckcnt = 1;
#if defined(__x86)
                page_downgrade(pp);
#else
                if (vmflag & SEGKMEM_SHARELOCKED)
                        page_downgrade(pp);
                else
                        page_unlock(pp);
#endif
        }

        return (addr);
}

static void *
segkmem_alloc_vn(vmem_t *vmp, size_t size, int vmflag, struct vnode *vp)
{
        void *addr;
        segkmem_gc_list_t *gcp, **prev_gcpp;

        ASSERT(vp != NULL);

        if (kvseg.s_base == NULL) {
                if (bootops->bsys_alloc == NULL)
                        halt("Memory allocation between bop_alloc() and "
                            "kmem_alloc().\n");

                /*
                 * There's not a lot of memory to go around during boot,
                 * so recycle it if we can.
                 */
                for (prev_gcpp = &segkmem_gc_list; (gcp = *prev_gcpp) != NULL;
                    prev_gcpp = &gcp->gc_next) {
                        if (gcp->gc_arena == vmp && gcp->gc_size == size) {
                                *prev_gcpp = gcp->gc_next;
                                return (gcp);
                        }
                }

                addr = vmem_alloc(vmp, size, vmflag | VM_PANIC);
                if (boot_alloc(addr, size, BO_NO_ALIGN) != addr)
                        panic("segkmem_alloc: boot_alloc failed");
                return (addr);
        }
        return (segkmem_xalloc(vmp, NULL, size, vmflag, 0,
            segkmem_page_create, vp));
}

void *
segkmem_alloc(vmem_t *vmp, size_t size, int vmflag)
{
        return (segkmem_alloc_vn(vmp, size, vmflag, &kvp));
}

void *
segkmem_zio_alloc(vmem_t *vmp, size_t size, int vmflag)
{
        return (segkmem_alloc_vn(vmp, size, vmflag, &zvp));
}

/*
 * Any changes to this routine must also be carried over to
 * devmap_free_pages() in the seg_dev driver. This is because
 * we currently don't have a special kernel segment for non-paged
 * kernel memory that is exported by drivers to user space.
 */
static void
segkmem_free_vn(vmem_t *vmp, void *inaddr, size_t size, struct vnode *vp,
    void (*func)(page_t *))
{
        page_t *pp;
        caddr_t addr = inaddr;
        caddr_t eaddr;
        pgcnt_t npages = btopr(size);

        ASSERT(((uintptr_t)addr & PAGEOFFSET) == 0);
        ASSERT(vp != NULL);

        if (kvseg.s_base == NULL) {
                segkmem_gc_list_t *gc = inaddr;
                gc->gc_arena = vmp;
                gc->gc_size = size;
                gc->gc_next = segkmem_gc_list;
                segkmem_gc_list = gc;
                return;
        }

        hat_unload(kas.a_hat, addr, size, HAT_UNLOAD_UNLOCK);

        for (eaddr = addr + size; addr < eaddr; addr += PAGESIZE) {
#if defined(__x86)
                pp = page_find(&vp->v_object, (uoff_t)(uintptr_t)addr);
                if (pp == NULL)
                        panic("segkmem_free: page not found");
                if (!page_tryupgrade(pp)) {
                        /*
                         * Some other thread has a sharelock. Wait for
                         * it to drop the lock so we can free this page.
                         */
                        page_unlock(pp);
                        pp = page_lookup(&vp->v_object, (uoff_t)(uintptr_t)addr,
                            SE_EXCL);
                }
#else
                pp = page_lookup(&vp->v_object, (uoff_t)(uintptr_t)addr,
                                 SE_EXCL);
#endif
                if (pp == NULL)
                        panic("segkmem_free: page not found");
                /* Clear p_lckcnt so page_destroy() doesn't update availrmem */
                pp->p_lckcnt = 0;
                if (func)
                        func(pp);
                else
                        page_destroy(pp, 0);
        }
        if (func == NULL)
                page_unresv(npages);

        if (vmp != NULL)
                vmem_free(vmp, inaddr, size);

}

void
segkmem_xfree(vmem_t *vmp, void *inaddr, size_t size, void (*func)(page_t *))
{
        segkmem_free_vn(vmp, inaddr, size, &kvp, func);
}

void
segkmem_free(vmem_t *vmp, void *inaddr, size_t size)
{
        segkmem_free_vn(vmp, inaddr, size, &kvp, NULL);
}

void
segkmem_zio_free(vmem_t *vmp, void *inaddr, size_t size)
{
        segkmem_free_vn(vmp, inaddr, size, &zvp, NULL);
}

void
segkmem_gc(void)
{
        ASSERT(kvseg.s_base != NULL);
        while (segkmem_gc_list != NULL) {
                segkmem_gc_list_t *gc = segkmem_gc_list;
                segkmem_gc_list = gc->gc_next;
                segkmem_free(gc->gc_arena, gc, gc->gc_size);
        }
}

/*
 * Legacy entry points from here to end of file.
 */
void
segkmem_mapin(struct seg *seg, void *addr, size_t size, uint_t vprot,
    pfn_t pfn, uint_t flags)
{
        hat_unload(seg->s_as->a_hat, addr, size, HAT_UNLOAD_UNLOCK);
        hat_devload(seg->s_as->a_hat, addr, size, pfn, vprot,
            flags | HAT_LOAD_LOCK);
}

void
segkmem_mapout(struct seg *seg, void *addr, size_t size)
{
        hat_unload(seg->s_as->a_hat, addr, size, HAT_UNLOAD_UNLOCK);
}

void *
kmem_getpages(pgcnt_t npages, int kmflag)
{
        return (kmem_alloc(ptob(npages), kmflag));
}

void
kmem_freepages(void *addr, pgcnt_t npages)
{
        kmem_free(addr, ptob(npages));
}

/*
 * segkmem_page_create_large() allocates a large page to be used for the kmem
 * caches. If kpr is enabled we ask for a relocatable page unless requested
 * otherwise. If kpr is disabled we have to ask for a non-reloc page
 */
static page_t *
segkmem_page_create_large(void *addr, size_t size, int vmflag, void *arg)
{
        int pgflags;

        pgflags = PG_EXCL;

        if (segkmem_reloc == 0 || (vmflag & VM_NORELOC))
                pgflags |= PG_NORELOC;
        if (!(vmflag & VM_NOSLEEP))
                pgflags |= PG_WAIT;
        if (vmflag & VM_PUSHPAGE)
                pgflags |= PG_PUSHPAGE;
        if (vmflag & VM_NORMALPRI)
                pgflags |= PG_NORMALPRI;

        return (page_create_va_large(&kvp.v_object, (uoff_t)(uintptr_t)addr,
                                     size, pgflags, &kvseg, addr, arg));
}

/*
 * Allocate a large page to back the virtual address range
 * [addr, addr + size).  If addr is NULL, allocate the virtual address
 * space as well.
 */
static void *
segkmem_xalloc_lp(vmem_t *vmp, void *inaddr, size_t size, int vmflag,
    uint_t attr, page_t *(*page_create_func)(void *, size_t, int, void *),
    void *pcarg)
{
        caddr_t addr = inaddr, pa;
        size_t  lpsize = segkmem_lpsize;
        pgcnt_t npages = btopr(size);
        pgcnt_t nbpages = btop(lpsize);
        pgcnt_t nlpages = size >> segkmem_lpshift;
        size_t  ppasize = nbpages * sizeof (page_t *);
        page_t *pp, *rootpp, **ppa, *pplist = NULL;
        int i;

        vmflag |= VM_NOSLEEP;

        if (page_resv(npages, vmflag & VM_KMFLAGS) == 0) {
                return (NULL);
        }

        /*
         * allocate an array we need for hat_memload_array.
         * we use a separate arena to avoid recursion.
         * we will not need this array when hat_memload_array learns pp++
         */
        if ((ppa = vmem_alloc(segkmem_ppa_arena, ppasize, vmflag)) == NULL) {
                goto fail_array_alloc;
        }

        if (inaddr == NULL && (addr = vmem_alloc(vmp, size, vmflag)) == NULL)
                goto fail_vmem_alloc;

        ASSERT(((uintptr_t)addr & (lpsize - 1)) == 0);

        /* create all the pages */
        for (pa = addr, i = 0; i < nlpages; i++, pa += lpsize) {
                if ((pp = page_create_func(pa, lpsize, vmflag, pcarg)) == NULL)
                        goto fail_page_create;
                page_list_concat(&pplist, &pp);
        }

        /* at this point we have all the resource to complete the request */
        while ((rootpp = pplist) != NULL) {
                for (i = 0; i < nbpages; i++) {
                        ASSERT(pplist != NULL);
                        pp = pplist;
                        page_sub(&pplist, pp);
                        ASSERT(page_iolock_assert(pp));
                        page_io_unlock(pp);
                        ppa[i] = pp;
                }
                /*
                 * Load the locked entry. It's OK to preload the entry into the
                 * TSB since we now support large mappings in the kernel TSB.
                 */
                hat_memload_array(kas.a_hat,
                    (caddr_t)(uintptr_t)rootpp->p_offset, lpsize,
                    ppa, (PROT_ALL & ~PROT_USER) | HAT_NOSYNC | attr,
                    HAT_LOAD_LOCK);

                for (--i; i >= 0; --i) {
                        ppa[i]->p_lckcnt = 1;
                        page_unlock(ppa[i]);
                }
        }

        vmem_free(segkmem_ppa_arena, ppa, ppasize);
        return (addr);

fail_page_create:
        while ((rootpp = pplist) != NULL) {
                for (i = 0, pp = pplist; i < nbpages; i++, pp = pplist) {
                        ASSERT(pp != NULL);
                        page_sub(&pplist, pp);
                        ASSERT(page_iolock_assert(pp));
                        page_io_unlock(pp);
                }
                page_destroy_pages(rootpp);
        }

        if (inaddr == NULL)
                vmem_free(vmp, addr, size);

fail_vmem_alloc:
        vmem_free(segkmem_ppa_arena, ppa, ppasize);

fail_array_alloc:
        page_unresv(npages);

        return (NULL);
}

static void
segkmem_free_one_lp(caddr_t addr, size_t size)
{
        page_t          *pp, *rootpp = NULL;
        pgcnt_t         pgs_left = btopr(size);

        ASSERT(size == segkmem_lpsize);

        hat_unload(kas.a_hat, addr, size, HAT_UNLOAD_UNLOCK);

        for (; pgs_left > 0; addr += PAGESIZE, pgs_left--) {
                pp = page_lookup(&kvp.v_object, (uoff_t)(uintptr_t)addr, SE_EXCL);
                if (pp == NULL)
                        panic("segkmem_free_one_lp: page not found");
                ASSERT(PAGE_EXCL(pp));
                pp->p_lckcnt = 0;
                if (rootpp == NULL)
                        rootpp = pp;
        }
        ASSERT(rootpp != NULL);
        page_destroy_pages(rootpp);

        /* page_unresv() is done by the caller */
}

/*
 * This function is called to import new spans into the vmem arenas like
 * kmem_default_arena and kmem_oversize_arena. It first tries to import
 * spans from large page arena - kmem_lp_arena. In order to do this it might
 * have to "upgrade the requested size" to kmem_lp_arena quantum. If
 * it was not able to satisfy the upgraded request it then calls regular
 * segkmem_alloc() that satisfies the request by importing from "*vmp" arena
 */
/*ARGSUSED*/
void *
segkmem_alloc_lp(vmem_t *vmp, size_t *sizep, size_t align, int vmflag)
{
        size_t size;
        kthread_t *t = curthread;
        segkmem_lpcb_t *lpcb = &segkmem_lpcb;

        ASSERT(sizep != NULL);

        size = *sizep;

        if (lpcb->lp_uselp && !(t->t_flag & T_PANIC) &&
            !(vmflag & SEGKMEM_SHARELOCKED)) {

                size_t kmemlp_qnt = segkmem_kmemlp_quantum;
                size_t asize = P2ROUNDUP(size, kmemlp_qnt);
                void  *addr = NULL;
                ulong_t *lpthrtp = &lpcb->lp_throttle;
                ulong_t lpthrt = *lpthrtp;
                int     dowakeup = 0;
                int     doalloc = 1;

                ASSERT(kmem_lp_arena != NULL);
                ASSERT(asize >= size);

                if (lpthrt != 0) {
                        /* try to update the throttle value */
                        lpthrt = atomic_inc_ulong_nv(lpthrtp);
                        if (lpthrt >= segkmem_lpthrottle_max) {
                                lpthrt = atomic_cas_ulong(lpthrtp, lpthrt,
                                    segkmem_lpthrottle_max / 4);
                        }

                        /*
                         * when we get above throttle start do an exponential
                         * backoff at trying large pages and reaping
                         */
                        if (lpthrt > segkmem_lpthrottle_start &&
                            !ISP2(lpthrt)) {
                                lpcb->allocs_throttled++;
                                lpthrt--;
                                if (ISP2(lpthrt))
                                        kmem_reap();
                                return (segkmem_alloc(vmp, size, vmflag));
                        }
                }

                if (!(vmflag & VM_NOSLEEP) &&
                    segkmem_heaplp_quantum >= (8 * kmemlp_qnt) &&
                    vmem_size(kmem_lp_arena, VMEM_FREE) <= kmemlp_qnt &&
                    asize < (segkmem_heaplp_quantum - kmemlp_qnt)) {

                        /*
                         * we are low on free memory in kmem_lp_arena
                         * we let only one guy to allocate heap_lp
                         * quantum size chunk that everybody is going to
                         * share
                         */
                        mutex_enter(&lpcb->lp_lock);

                        if (lpcb->lp_wait) {

                                /* we are not the first one - wait */
                                cv_wait(&lpcb->lp_cv, &lpcb->lp_lock);
                                if (vmem_size(kmem_lp_arena, VMEM_FREE) <
                                    kmemlp_qnt)  {
                                        doalloc = 0;
                                }
                        } else if (vmem_size(kmem_lp_arena, VMEM_FREE) <=
                            kmemlp_qnt) {

                                /*
                                 * we are the first one, make sure we import
                                 * a large page
                                 */
                                if (asize == kmemlp_qnt)
                                        asize += kmemlp_qnt;
                                dowakeup = 1;
                                lpcb->lp_wait = 1;
                        }

                        mutex_exit(&lpcb->lp_lock);
                }

                /*
                 * VM_ABORT flag prevents sleeps in vmem_xalloc when
                 * large pages are not available. In that case this allocation
                 * attempt will fail and we will retry allocation with small
                 * pages. We also do not want to panic if this allocation fails
                 * because we are going to retry.
                 */
                if (doalloc) {
                        addr = vmem_alloc(kmem_lp_arena, asize,
                            (vmflag | VM_ABORT) & ~VM_PANIC);

                        if (dowakeup) {
                                mutex_enter(&lpcb->lp_lock);
                                ASSERT(lpcb->lp_wait != 0);
                                lpcb->lp_wait = 0;
                                cv_broadcast(&lpcb->lp_cv);
                                mutex_exit(&lpcb->lp_lock);
                        }
                }

                if (addr != NULL) {
                        *sizep = asize;
                        *lpthrtp = 0;
                        return (addr);
                }

                if (vmflag & VM_NOSLEEP)
                        lpcb->nosleep_allocs_failed++;
                else
                        lpcb->sleep_allocs_failed++;
                lpcb->alloc_bytes_failed += size;

                /* if large page throttling is not started yet do it */
                if (segkmem_use_lpthrottle && lpthrt == 0) {
                        lpthrt = atomic_cas_ulong(lpthrtp, lpthrt, 1);
                }
        }
        return (segkmem_alloc(vmp, size, vmflag));
}

void
segkmem_free_lp(vmem_t *vmp, void *inaddr, size_t size)
{
        if (kmem_lp_arena == NULL || !IS_KMEM_VA_LARGEPAGE((caddr_t)inaddr)) {
                segkmem_free(vmp, inaddr, size);
        } else {
                vmem_free(kmem_lp_arena, inaddr, size);
        }
}

/*
 * segkmem_alloc_lpi() imports virtual memory from large page heap arena
 * into kmem_lp arena. In the process it maps the imported segment with
 * large pages
 */
static void *
segkmem_alloc_lpi(vmem_t *vmp, size_t size, int vmflag)
{
        segkmem_lpcb_t *lpcb = &segkmem_lpcb;
        void  *addr;

        ASSERT(size != 0);
        ASSERT(vmp == heap_lp_arena);

        /* do not allow large page heap grow beyound limits */
        if (vmem_size(vmp, VMEM_ALLOC) >= segkmem_kmemlp_max) {
                lpcb->allocs_limited++;
                return (NULL);
        }

        addr = segkmem_xalloc_lp(vmp, NULL, size, vmflag, 0,
            segkmem_page_create_large, NULL);
        return (addr);
}

/*
 * segkmem_free_lpi() returns virtual memory back into large page heap arena
 * from kmem_lp arena. Beore doing this it unmaps the segment and frees
 * large pages used to map it.
 */
static void
segkmem_free_lpi(vmem_t *vmp, void *inaddr, size_t size)
{
        pgcnt_t         nlpages = size >> segkmem_lpshift;
        size_t          lpsize = segkmem_lpsize;
        caddr_t         addr = inaddr;
        pgcnt_t         npages = btopr(size);
        int             i;

        ASSERT(vmp == heap_lp_arena);
        ASSERT(IS_KMEM_VA_LARGEPAGE(addr));
        ASSERT(((uintptr_t)inaddr & (lpsize - 1)) == 0);

        for (i = 0; i < nlpages; i++) {
                segkmem_free_one_lp(addr, lpsize);
                addr += lpsize;
        }

        page_unresv(npages);

        vmem_free(vmp, inaddr, size);
}

/*
 * This function is called at system boot time by kmem_init right after
 * /etc/system file has been read. It checks based on hardware configuration
 * and /etc/system settings if system is going to use large pages. The
 * initialiazation necessary to actually start using large pages
 * happens later in the process after segkmem_heap_lp_init() is called.
 */
int
segkmem_lpsetup()
{
        int use_large_pages = 0;

        return (use_large_pages);
}

void
segkmem_zio_init(void *zio_mem_base, size_t zio_mem_size)
{
        ASSERT(zio_mem_base != NULL);
        ASSERT(zio_mem_size != 0);

        /*
         * To reduce VA space fragmentation, we set up quantum caches for the
         * smaller sizes;  we chose 32k because that translates to 128k VA
         * slabs, which matches nicely with the common 128k zio_data bufs.
         */
        zio_arena = vmem_create("zfs_file_data", zio_mem_base, zio_mem_size,
            PAGESIZE, NULL, NULL, NULL, 32 * 1024, VM_SLEEP);

        zio_alloc_arena = vmem_create("zfs_file_data_buf", NULL, 0, PAGESIZE,
            segkmem_zio_alloc, segkmem_zio_free, zio_arena, 0, VM_SLEEP);

        ASSERT(zio_arena != NULL);
        ASSERT(zio_alloc_arena != NULL);
}