| /* |
| * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC. |
| * Copyright (C) 2007 The Regents of the University of California. |
| * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER). |
| * Written by Brian Behlendorf <behlendorf1@llnl.gov>. |
| * UCRL-CODE-235197 |
| * |
| * This file is part of the SPL, Solaris Porting Layer. |
| * For details, see <http://zfsonlinux.org/>. |
| * |
| * The SPL is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License as published by the |
| * Free Software Foundation; either version 2 of the License, or (at your |
| * option) any later version. |
| * |
| * The SPL is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * for more details. |
| * |
| * You should have received a copy of the GNU General Public License along |
| * with the SPL. If not, see <http://www.gnu.org/licenses/>. |
| */ |
| |
| #ifndef _SPL_VMEM_H |
| #define _SPL_VMEM_H |
| |
| #include <sys/kmem.h> |
| #include <linux/sched.h> |
| #include <linux/vmalloc.h> |
| |
| typedef struct vmem { } vmem_t; |
| |
| extern vmem_t *heap_arena; |
| extern vmem_t *zio_alloc_arena; |
| extern vmem_t *zio_arena; |
| |
| extern size_t vmem_size(vmem_t *vmp, int typemask); |
| |
| /* |
| * Memory allocation interfaces |
| */ |
| #define VMEM_ALLOC 0x01 |
| #define VMEM_FREE 0x02 |
| |
| #ifndef VMALLOC_TOTAL |
| #define VMALLOC_TOTAL (VMALLOC_END - VMALLOC_START) |
| #endif |
| |
| /* |
| * vmem_* is an interface to a low level arena-based memory allocator on |
| * Illumos that is used to allocate virtual address space. The kmem SLAB |
| * allocator allocates slabs from it. Then the generic allocation functions |
| * kmem_{alloc,zalloc,free}() are layered on top of SLAB allocators. |
| * |
| * On Linux, the primary means of doing allocations is via kmalloc(), which |
| * is similarly layered on top of something called the buddy allocator. The |
| * buddy allocator is not available to kernel modules, it uses physical |
| * memory addresses rather than virtual memory addresses and is prone to |
| * fragmentation. |
| * |
| * Linux sets aside a relatively small address space for in-kernel virtual |
| * memory from which allocations can be done using vmalloc(). It might seem |
| * like a good idea to use vmalloc() to implement something similar to |
| * Illumos' allocator. However, this has the following problems: |
| * |
| * 1. Page directory table allocations are hard coded to use GFP_KERNEL. |
| * Consequently, any KM_PUSHPAGE or KM_NOSLEEP allocations done using |
| * vmalloc() will not have proper semantics. |
| * |
| * 2. Address space exhaustion is a real issue on 32-bit platforms where |
| * only a few 100MB are available. The kernel will handle it by spinning |
| * when it runs out of address space. |
| * |
| * 3. All vmalloc() allocations and frees are protected by a single global |
| * lock which serializes all allocations. |
| * |
| * 4. Accessing /proc/meminfo and /proc/vmallocinfo will iterate the entire |
| * list. The former will sum the allocations while the latter will print |
| * them to user space in a way that user space can keep the lock held |
| * indefinitely. When the total number of mapped allocations is large |
| * (several 100,000) a large amount of time will be spent waiting on locks. |
| * |
| * 5. Linux has a wait_on_bit() locking primitive that assumes physical |
| * memory is used, it simply does not work on virtual memory. Certain |
| * Linux structures (e.g. the superblock) use them and might be embedded |
| * into a structure from Illumos. This makes using Linux virtual memory |
| * unsafe in certain situations. |
| * |
| * It follows that we cannot obtain identical semantics to those on Illumos. |
| * Consequently, we implement the kmem_{alloc,zalloc,free}() functions in |
| * such a way that they can be used as drop-in replacements for small vmem_* |
| * allocations (8MB in size or smaller) and map vmem_{alloc,zalloc,free}() |
| * to them. |
| */ |
| |
| #define vmem_alloc(sz, fl) spl_vmem_alloc((sz), (fl), __func__, __LINE__) |
| #define vmem_zalloc(sz, fl) spl_vmem_zalloc((sz), (fl), __func__, __LINE__) |
| #define vmem_free(ptr, sz) spl_vmem_free((ptr), (sz)) |
| #define vmem_qcache_reap(ptr) ((void)0) |
| |
| extern void *spl_vmem_alloc(size_t sz, int fl, const char *func, int line); |
| extern void *spl_vmem_zalloc(size_t sz, int fl, const char *func, int line); |
| extern void spl_vmem_free(const void *ptr, size_t sz); |
| |
| int spl_vmem_init(void); |
| void spl_vmem_fini(void); |
| |
| #endif /* _SPL_VMEM_H */ |