mirror_zfs/include/sys/arc_impl.h
Matthew Macy c9c9c1e213 OpenZFS restructuring - ARC memory pressure
Factor Linux specific memory pressure handling out of ARC.  Each
platform will have different available interfaces for managing memory
pressure.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes #9472
2019-10-18 13:23:19 -04:00

620 lines
22 KiB
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) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2013 by Delphix. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
* Copyright 2013 Nexenta Systems, Inc. All rights reserved.
*/
#ifndef _SYS_ARC_IMPL_H
#define _SYS_ARC_IMPL_H
#include <sys/arc.h>
#include <sys/zio_crypt.h>
#include <sys/zthr.h>
#include <sys/aggsum.h>
#ifdef __cplusplus
extern "C" {
#endif
/*
* Note that buffers can be in one of 6 states:
* ARC_anon - anonymous (discussed below)
* ARC_mru - recently used, currently cached
* ARC_mru_ghost - recently used, no longer in cache
* ARC_mfu - frequently used, currently cached
* ARC_mfu_ghost - frequently used, no longer in cache
* ARC_l2c_only - exists in L2ARC but not other states
* When there are no active references to the buffer, they are
* are linked onto a list in one of these arc states. These are
* the only buffers that can be evicted or deleted. Within each
* state there are multiple lists, one for meta-data and one for
* non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
* etc.) is tracked separately so that it can be managed more
* explicitly: favored over data, limited explicitly.
*
* Anonymous buffers are buffers that are not associated with
* a DVA. These are buffers that hold dirty block copies
* before they are written to stable storage. By definition,
* they are "ref'd" and are considered part of arc_mru
* that cannot be freed. Generally, they will acquire a DVA
* as they are written and migrate onto the arc_mru list.
*
* The ARC_l2c_only state is for buffers that are in the second
* level ARC but no longer in any of the ARC_m* lists. The second
* level ARC itself may also contain buffers that are in any of
* the ARC_m* states - meaning that a buffer can exist in two
* places. The reason for the ARC_l2c_only state is to keep the
* buffer header in the hash table, so that reads that hit the
* second level ARC benefit from these fast lookups.
*/
typedef struct arc_state {
/*
* list of evictable buffers
*/
multilist_t *arcs_list[ARC_BUFC_NUMTYPES];
/*
* total amount of evictable data in this state
*/
zfs_refcount_t arcs_esize[ARC_BUFC_NUMTYPES];
/*
* total amount of data in this state; this includes: evictable,
* non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA.
*/
zfs_refcount_t arcs_size;
/*
* supports the "dbufs" kstat
*/
arc_state_type_t arcs_state;
} arc_state_t;
typedef struct arc_callback arc_callback_t;
struct arc_callback {
void *acb_private;
arc_read_done_func_t *acb_done;
arc_buf_t *acb_buf;
boolean_t acb_encrypted;
boolean_t acb_compressed;
boolean_t acb_noauth;
zbookmark_phys_t acb_zb;
zio_t *acb_zio_dummy;
zio_t *acb_zio_head;
arc_callback_t *acb_next;
};
typedef struct arc_write_callback arc_write_callback_t;
struct arc_write_callback {
void *awcb_private;
arc_write_done_func_t *awcb_ready;
arc_write_done_func_t *awcb_children_ready;
arc_write_done_func_t *awcb_physdone;
arc_write_done_func_t *awcb_done;
arc_buf_t *awcb_buf;
};
/*
* ARC buffers are separated into multiple structs as a memory saving measure:
* - Common fields struct, always defined, and embedded within it:
* - L2-only fields, always allocated but undefined when not in L2ARC
* - L1-only fields, only allocated when in L1ARC
*
* Buffer in L1 Buffer only in L2
* +------------------------+ +------------------------+
* | arc_buf_hdr_t | | arc_buf_hdr_t |
* | | | |
* | | | |
* | | | |
* +------------------------+ +------------------------+
* | l2arc_buf_hdr_t | | l2arc_buf_hdr_t |
* | (undefined if L1-only) | | |
* +------------------------+ +------------------------+
* | l1arc_buf_hdr_t |
* | |
* | |
* | |
* | |
* +------------------------+
*
* Because it's possible for the L2ARC to become extremely large, we can wind
* up eating a lot of memory in L2ARC buffer headers, so the size of a header
* is minimized by only allocating the fields necessary for an L1-cached buffer
* when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and
* l2arc_buf_hdr) are embedded rather than allocated separately to save a couple
* words in pointers. arc_hdr_realloc() is used to switch a header between
* these two allocation states.
*/
typedef struct l1arc_buf_hdr {
kmutex_t b_freeze_lock;
zio_cksum_t *b_freeze_cksum;
arc_buf_t *b_buf;
uint32_t b_bufcnt;
/* for waiting on writes to complete */
kcondvar_t b_cv;
uint8_t b_byteswap;
/* protected by arc state mutex */
arc_state_t *b_state;
multilist_node_t b_arc_node;
/* updated atomically */
clock_t b_arc_access;
uint32_t b_mru_hits;
uint32_t b_mru_ghost_hits;
uint32_t b_mfu_hits;
uint32_t b_mfu_ghost_hits;
uint32_t b_l2_hits;
/* self protecting */
zfs_refcount_t b_refcnt;
arc_callback_t *b_acb;
abd_t *b_pabd;
} l1arc_buf_hdr_t;
/*
* Encrypted blocks will need to be stored encrypted on the L2ARC
* disk as they appear in the main pool. In order for this to work we
* need to pass around the encryption parameters so they can be used
* to write data to the L2ARC. This struct is only defined in the
* arc_buf_hdr_t if the L1 header is defined and has the ARC_FLAG_ENCRYPTED
* flag set.
*/
typedef struct arc_buf_hdr_crypt {
abd_t *b_rabd; /* raw encrypted data */
dmu_object_type_t b_ot; /* object type */
uint32_t b_ebufcnt; /* count of encrypted buffers */
/* dsobj for looking up encryption key for l2arc encryption */
uint64_t b_dsobj;
/* encryption parameters */
uint8_t b_salt[ZIO_DATA_SALT_LEN];
uint8_t b_iv[ZIO_DATA_IV_LEN];
/*
* Technically this could be removed since we will always be able to
* get the mac from the bp when we need it. However, it is inconvenient
* for callers of arc code to have to pass a bp in all the time. This
* also allows us to assert that L2ARC data is properly encrypted to
* match the data in the main storage pool.
*/
uint8_t b_mac[ZIO_DATA_MAC_LEN];
} arc_buf_hdr_crypt_t;
typedef struct l2arc_dev {
vdev_t *l2ad_vdev; /* vdev */
spa_t *l2ad_spa; /* spa */
uint64_t l2ad_hand; /* next write location */
uint64_t l2ad_start; /* first addr on device */
uint64_t l2ad_end; /* last addr on device */
boolean_t l2ad_first; /* first sweep through */
boolean_t l2ad_writing; /* currently writing */
kmutex_t l2ad_mtx; /* lock for buffer list */
list_t l2ad_buflist; /* buffer list */
list_node_t l2ad_node; /* device list node */
zfs_refcount_t l2ad_alloc; /* allocated bytes */
} l2arc_dev_t;
typedef struct l2arc_buf_hdr {
/* protected by arc_buf_hdr mutex */
l2arc_dev_t *b_dev; /* L2ARC device */
uint64_t b_daddr; /* disk address, offset byte */
uint32_t b_hits;
list_node_t b_l2node;
} l2arc_buf_hdr_t;
typedef struct l2arc_write_callback {
l2arc_dev_t *l2wcb_dev; /* device info */
arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
} l2arc_write_callback_t;
struct arc_buf_hdr {
/* protected by hash lock */
dva_t b_dva;
uint64_t b_birth;
arc_buf_contents_t b_type;
arc_buf_hdr_t *b_hash_next;
arc_flags_t b_flags;
/*
* This field stores the size of the data buffer after
* compression, and is set in the arc's zio completion handlers.
* It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes).
*
* While the block pointers can store up to 32MB in their psize
* field, we can only store up to 32MB minus 512B. This is due
* to the bp using a bias of 1, whereas we use a bias of 0 (i.e.
* a field of zeros represents 512B in the bp). We can't use a
* bias of 1 since we need to reserve a psize of zero, here, to
* represent holes and embedded blocks.
*
* This isn't a problem in practice, since the maximum size of a
* buffer is limited to 16MB, so we never need to store 32MB in
* this field. Even in the upstream illumos code base, the
* maximum size of a buffer is limited to 16MB.
*/
uint16_t b_psize;
/*
* This field stores the size of the data buffer before
* compression, and cannot change once set. It is in units
* of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes)
*/
uint16_t b_lsize; /* immutable */
uint64_t b_spa; /* immutable */
/* L2ARC fields. Undefined when not in L2ARC. */
l2arc_buf_hdr_t b_l2hdr;
/* L1ARC fields. Undefined when in l2arc_only state */
l1arc_buf_hdr_t b_l1hdr;
/*
* Encryption parameters. Defined only when ARC_FLAG_ENCRYPTED
* is set and the L1 header exists.
*/
arc_buf_hdr_crypt_t b_crypt_hdr;
};
typedef struct arc_stats {
kstat_named_t arcstat_hits;
kstat_named_t arcstat_misses;
kstat_named_t arcstat_demand_data_hits;
kstat_named_t arcstat_demand_data_misses;
kstat_named_t arcstat_demand_metadata_hits;
kstat_named_t arcstat_demand_metadata_misses;
kstat_named_t arcstat_prefetch_data_hits;
kstat_named_t arcstat_prefetch_data_misses;
kstat_named_t arcstat_prefetch_metadata_hits;
kstat_named_t arcstat_prefetch_metadata_misses;
kstat_named_t arcstat_mru_hits;
kstat_named_t arcstat_mru_ghost_hits;
kstat_named_t arcstat_mfu_hits;
kstat_named_t arcstat_mfu_ghost_hits;
kstat_named_t arcstat_deleted;
/*
* Number of buffers that could not be evicted because the hash lock
* was held by another thread. The lock may not necessarily be held
* by something using the same buffer, since hash locks are shared
* by multiple buffers.
*/
kstat_named_t arcstat_mutex_miss;
/*
* Number of buffers skipped when updating the access state due to the
* header having already been released after acquiring the hash lock.
*/
kstat_named_t arcstat_access_skip;
/*
* Number of buffers skipped because they have I/O in progress, are
* indirect prefetch buffers that have not lived long enough, or are
* not from the spa we're trying to evict from.
*/
kstat_named_t arcstat_evict_skip;
/*
* Number of times arc_evict_state() was unable to evict enough
* buffers to reach its target amount.
*/
kstat_named_t arcstat_evict_not_enough;
kstat_named_t arcstat_evict_l2_cached;
kstat_named_t arcstat_evict_l2_eligible;
kstat_named_t arcstat_evict_l2_ineligible;
kstat_named_t arcstat_evict_l2_skip;
kstat_named_t arcstat_hash_elements;
kstat_named_t arcstat_hash_elements_max;
kstat_named_t arcstat_hash_collisions;
kstat_named_t arcstat_hash_chains;
kstat_named_t arcstat_hash_chain_max;
kstat_named_t arcstat_p;
kstat_named_t arcstat_c;
kstat_named_t arcstat_c_min;
kstat_named_t arcstat_c_max;
/* Not updated directly; only synced in arc_kstat_update. */
kstat_named_t arcstat_size;
/*
* Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd.
* Note that the compressed bytes may match the uncompressed bytes
* if the block is either not compressed or compressed arc is disabled.
*/
kstat_named_t arcstat_compressed_size;
/*
* Uncompressed size of the data stored in b_pabd. If compressed
* arc is disabled then this value will be identical to the stat
* above.
*/
kstat_named_t arcstat_uncompressed_size;
/*
* Number of bytes stored in all the arc_buf_t's. This is classified
* as "overhead" since this data is typically short-lived and will
* be evicted from the arc when it becomes unreferenced unless the
* zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level
* values have been set (see comment in dbuf.c for more information).
*/
kstat_named_t arcstat_overhead_size;
/*
* Number of bytes consumed by internal ARC structures necessary
* for tracking purposes; these structures are not actually
* backed by ARC buffers. This includes arc_buf_hdr_t structures
* (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
* caches), and arc_buf_t structures (allocated via arc_buf_t
* cache).
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_hdr_size;
/*
* Number of bytes consumed by ARC buffers of type equal to
* ARC_BUFC_DATA. This is generally consumed by buffers backing
* on disk user data (e.g. plain file contents).
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_data_size;
/*
* Number of bytes consumed by ARC buffers of type equal to
* ARC_BUFC_METADATA. This is generally consumed by buffers
* backing on disk data that is used for internal ZFS
* structures (e.g. ZAP, dnode, indirect blocks, etc).
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_metadata_size;
/*
* Number of bytes consumed by dmu_buf_impl_t objects.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_dbuf_size;
/*
* Number of bytes consumed by dnode_t objects.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_dnode_size;
/*
* Number of bytes consumed by bonus buffers.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_bonus_size;
/*
* Total number of bytes consumed by ARC buffers residing in the
* arc_anon state. This includes *all* buffers in the arc_anon
* state; e.g. data, metadata, evictable, and unevictable buffers
* are all included in this value.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_anon_size;
/*
* Number of bytes consumed by ARC buffers that meet the
* following criteria: backing buffers of type ARC_BUFC_DATA,
* residing in the arc_anon state, and are eligible for eviction
* (e.g. have no outstanding holds on the buffer).
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_anon_evictable_data;
/*
* Number of bytes consumed by ARC buffers that meet the
* following criteria: backing buffers of type ARC_BUFC_METADATA,
* residing in the arc_anon state, and are eligible for eviction
* (e.g. have no outstanding holds on the buffer).
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_anon_evictable_metadata;
/*
* Total number of bytes consumed by ARC buffers residing in the
* arc_mru state. This includes *all* buffers in the arc_mru
* state; e.g. data, metadata, evictable, and unevictable buffers
* are all included in this value.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mru_size;
/*
* Number of bytes consumed by ARC buffers that meet the
* following criteria: backing buffers of type ARC_BUFC_DATA,
* residing in the arc_mru state, and are eligible for eviction
* (e.g. have no outstanding holds on the buffer).
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mru_evictable_data;
/*
* Number of bytes consumed by ARC buffers that meet the
* following criteria: backing buffers of type ARC_BUFC_METADATA,
* residing in the arc_mru state, and are eligible for eviction
* (e.g. have no outstanding holds on the buffer).
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mru_evictable_metadata;
/*
* Total number of bytes that *would have been* consumed by ARC
* buffers in the arc_mru_ghost state. The key thing to note
* here, is the fact that this size doesn't actually indicate
* RAM consumption. The ghost lists only consist of headers and
* don't actually have ARC buffers linked off of these headers.
* Thus, *if* the headers had associated ARC buffers, these
* buffers *would have* consumed this number of bytes.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mru_ghost_size;
/*
* Number of bytes that *would have been* consumed by ARC
* buffers that are eligible for eviction, of type
* ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mru_ghost_evictable_data;
/*
* Number of bytes that *would have been* consumed by ARC
* buffers that are eligible for eviction, of type
* ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mru_ghost_evictable_metadata;
/*
* Total number of bytes consumed by ARC buffers residing in the
* arc_mfu state. This includes *all* buffers in the arc_mfu
* state; e.g. data, metadata, evictable, and unevictable buffers
* are all included in this value.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mfu_size;
/*
* Number of bytes consumed by ARC buffers that are eligible for
* eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
* state.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mfu_evictable_data;
/*
* Number of bytes consumed by ARC buffers that are eligible for
* eviction, of type ARC_BUFC_METADATA, and reside in the
* arc_mfu state.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mfu_evictable_metadata;
/*
* Total number of bytes that *would have been* consumed by ARC
* buffers in the arc_mfu_ghost state. See the comment above
* arcstat_mru_ghost_size for more details.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mfu_ghost_size;
/*
* Number of bytes that *would have been* consumed by ARC
* buffers that are eligible for eviction, of type
* ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mfu_ghost_evictable_data;
/*
* Number of bytes that *would have been* consumed by ARC
* buffers that are eligible for eviction, of type
* ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
* Not updated directly; only synced in arc_kstat_update.
*/
kstat_named_t arcstat_mfu_ghost_evictable_metadata;
kstat_named_t arcstat_l2_hits;
kstat_named_t arcstat_l2_misses;
kstat_named_t arcstat_l2_feeds;
kstat_named_t arcstat_l2_rw_clash;
kstat_named_t arcstat_l2_read_bytes;
kstat_named_t arcstat_l2_write_bytes;
kstat_named_t arcstat_l2_writes_sent;
kstat_named_t arcstat_l2_writes_done;
kstat_named_t arcstat_l2_writes_error;
kstat_named_t arcstat_l2_writes_lock_retry;
kstat_named_t arcstat_l2_evict_lock_retry;
kstat_named_t arcstat_l2_evict_reading;
kstat_named_t arcstat_l2_evict_l1cached;
kstat_named_t arcstat_l2_free_on_write;
kstat_named_t arcstat_l2_abort_lowmem;
kstat_named_t arcstat_l2_cksum_bad;
kstat_named_t arcstat_l2_io_error;
kstat_named_t arcstat_l2_lsize;
kstat_named_t arcstat_l2_psize;
/* Not updated directly; only synced in arc_kstat_update. */
kstat_named_t arcstat_l2_hdr_size;
kstat_named_t arcstat_memory_throttle_count;
kstat_named_t arcstat_memory_direct_count;
kstat_named_t arcstat_memory_indirect_count;
kstat_named_t arcstat_memory_all_bytes;
kstat_named_t arcstat_memory_free_bytes;
kstat_named_t arcstat_memory_available_bytes;
kstat_named_t arcstat_no_grow;
kstat_named_t arcstat_tempreserve;
kstat_named_t arcstat_loaned_bytes;
kstat_named_t arcstat_prune;
/* Not updated directly; only synced in arc_kstat_update. */
kstat_named_t arcstat_meta_used;
kstat_named_t arcstat_meta_limit;
kstat_named_t arcstat_dnode_limit;
kstat_named_t arcstat_meta_max;
kstat_named_t arcstat_meta_min;
kstat_named_t arcstat_async_upgrade_sync;
kstat_named_t arcstat_demand_hit_predictive_prefetch;
kstat_named_t arcstat_demand_hit_prescient_prefetch;
kstat_named_t arcstat_need_free;
kstat_named_t arcstat_sys_free;
kstat_named_t arcstat_raw_size;
} arc_stats_t;
typedef enum free_memory_reason_t {
FMR_UNKNOWN,
FMR_NEEDFREE,
FMR_LOTSFREE,
FMR_SWAPFS_MINFREE,
FMR_PAGES_PP_MAXIMUM,
FMR_HEAP_ARENA,
FMR_ZIO_ARENA,
} free_memory_reason_t;
#define ARCSTAT(stat) (arc_stats.stat.value.ui64)
#define ARCSTAT_INCR(stat, val) \
atomic_add_64(&arc_stats.stat.value.ui64, (val))
#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
#define arc_no_grow ARCSTAT(arcstat_no_grow) /* do not grow cache size */
#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
#define arc_c ARCSTAT(arcstat_c) /* target size of cache */
#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
#define arc_sys_free ARCSTAT(arcstat_sys_free) /* target system free bytes */
#define arc_need_free ARCSTAT(arcstat_need_free) /* bytes to be freed */
extern int arc_zio_arena_free_shift;
extern taskq_t *arc_prune_taskq;
extern arc_stats_t arc_stats;
extern hrtime_t arc_growtime;
extern boolean_t arc_warm;
extern int arc_grow_retry;
extern int arc_shrink_shift;
extern zthr_t *arc_adjust_zthr;
extern kmutex_t arc_adjust_lock;
extern kcondvar_t arc_adjust_waiters_cv;
extern boolean_t arc_adjust_needed;
extern kmutex_t arc_prune_mtx;
extern list_t arc_prune_list;
extern aggsum_t arc_size;
extern arc_state_t *arc_mfu;
extern arc_state_t *arc_mru;
extern uint_t zfs_arc_pc_percent;
extern int arc_lotsfree_percent;
extern void arc_reduce_target_size(int64_t to_free);
extern boolean_t arc_reclaim_needed(void);
extern void arc_kmem_reap_soon(void);
extern void arc_lowmem_init(void);
extern void arc_lowmem_fini(void);
extern void arc_prune_async(int64_t);
extern int arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg);
extern uint64_t arc_free_memory(void);
extern int64_t arc_available_memory(void);
#ifdef __cplusplus
}
#endif
#endif /* _SYS_ARC_IMPL_H */