linux/fs/ext4/mballoc.h
Ojaswin Mujoo f52f3d2b9f ext4: Give symbolic names to mballoc criterias
mballoc criterias have historically been called by numbers
like CR0, CR1... however this makes it confusing to understand
what each criteria is about.

Change these criterias from numbers to symbolic names and add
relevant comments. While we are at it, also reformat and add some
comments to ext4_seq_mb_stats_show() for better readability.

Additionally, define CR_FAST which signifies the criteria
below which we can make quicker decisions like:
  * quitting early if (free block < requested len)
  * avoiding to scan free extents smaller than required len.
  * avoiding to initialize buddy cache and work with existing cache
  * limiting prefetches

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/a2dc6ec5aea5e5e68cf8e788c2a964ffead9c8b0.1685449706.git.ojaswin@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2023-06-26 19:34:56 -04:00

253 lines
6.4 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* fs/ext4/mballoc.h
*
* Written by: Alex Tomas <alex@clusterfs.com>
*
*/
#ifndef _EXT4_MBALLOC_H
#define _EXT4_MBALLOC_H
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>
#include <linux/module.h>
#include <linux/swap.h>
#include <linux/proc_fs.h>
#include <linux/pagemap.h>
#include <linux/seq_file.h>
#include <linux/blkdev.h>
#include <linux/mutex.h>
#include "ext4_jbd2.h"
#include "ext4.h"
/*
* mb_debug() dynamic printk msgs could be used to debug mballoc code.
*/
#ifdef CONFIG_EXT4_DEBUG
#define mb_debug(sb, fmt, ...) \
pr_debug("[%s/%d] EXT4-fs (%s): (%s, %d): %s: " fmt, \
current->comm, task_pid_nr(current), sb->s_id, \
__FILE__, __LINE__, __func__, ##__VA_ARGS__)
#else
#define mb_debug(sb, fmt, ...) no_printk(fmt, ##__VA_ARGS__)
#endif
#define EXT4_MB_HISTORY_ALLOC 1 /* allocation */
#define EXT4_MB_HISTORY_PREALLOC 2 /* preallocated blocks used */
/*
* How long mballoc can look for a best extent (in found extents)
*/
#define MB_DEFAULT_MAX_TO_SCAN 200
/*
* How long mballoc must look for a best extent
*/
#define MB_DEFAULT_MIN_TO_SCAN 10
/*
* with 's_mb_stats' allocator will collect stats that will be
* shown at umount. The collecting costs though!
*/
#define MB_DEFAULT_STATS 0
/*
* files smaller than MB_DEFAULT_STREAM_THRESHOLD are served
* by the stream allocator, which purpose is to pack requests
* as close each to other as possible to produce smooth I/O traffic
* We use locality group prealloc space for stream request.
* We can tune the same via /proc/fs/ext4/<partition>/stream_req
*/
#define MB_DEFAULT_STREAM_THRESHOLD 16 /* 64K */
/*
* for which requests use 2^N search using buddies
*/
#define MB_DEFAULT_ORDER2_REQS 2
/*
* default group prealloc size 512 blocks
*/
#define MB_DEFAULT_GROUP_PREALLOC 512
/*
* Number of groups to search linearly before performing group scanning
* optimization.
*/
#define MB_DEFAULT_LINEAR_LIMIT 4
/*
* Minimum number of groups that should be present in the file system to perform
* group scanning optimizations.
*/
#define MB_DEFAULT_LINEAR_SCAN_THRESHOLD 16
/*
* The maximum order upto which CR_BEST_AVAIL_LEN can trim a particular
* allocation request. Example, if we have an order 7 request and max trim order
* of 3, we can trim this request upto order 4.
*/
#define MB_DEFAULT_BEST_AVAIL_TRIM_ORDER 3
/*
* Number of valid buddy orders
*/
#define MB_NUM_ORDERS(sb) ((sb)->s_blocksize_bits + 2)
struct ext4_free_data {
/* this links the free block information from sb_info */
struct list_head efd_list;
/* this links the free block information from group_info */
struct rb_node efd_node;
/* group which free block extent belongs */
ext4_group_t efd_group;
/* free block extent */
ext4_grpblk_t efd_start_cluster;
ext4_grpblk_t efd_count;
/* transaction which freed this extent */
tid_t efd_tid;
};
struct ext4_prealloc_space {
union {
struct rb_node inode_node; /* for inode PA rbtree */
struct list_head lg_list; /* for lg PAs */
} pa_node;
struct list_head pa_group_list;
union {
struct list_head pa_tmp_list;
struct rcu_head pa_rcu;
} u;
spinlock_t pa_lock;
atomic_t pa_count;
unsigned pa_deleted;
ext4_fsblk_t pa_pstart; /* phys. block */
ext4_lblk_t pa_lstart; /* log. block */
ext4_grpblk_t pa_len; /* len of preallocated chunk */
ext4_grpblk_t pa_free; /* how many blocks are free */
unsigned short pa_type; /* pa type. inode or group */
union {
rwlock_t *inode_lock; /* locks the rbtree holding this PA */
spinlock_t *lg_lock; /* locks the lg list holding this PA */
} pa_node_lock;
struct inode *pa_inode; /* used to get the inode during group discard */
};
enum {
MB_INODE_PA = 0,
MB_GROUP_PA = 1
};
struct ext4_free_extent {
ext4_lblk_t fe_logical;
ext4_grpblk_t fe_start; /* In cluster units */
ext4_group_t fe_group;
ext4_grpblk_t fe_len; /* In cluster units */
};
/*
* Locality group:
* we try to group all related changes together
* so that writeback can flush/allocate them together as well
* Size of lg_prealloc_list hash is determined by MB_DEFAULT_GROUP_PREALLOC
* (512). We store prealloc space into the hash based on the pa_free blocks
* order value.ie, fls(pa_free)-1;
*/
#define PREALLOC_TB_SIZE 10
struct ext4_locality_group {
/* for allocator */
/* to serialize allocates */
struct mutex lg_mutex;
/* list of preallocations */
struct list_head lg_prealloc_list[PREALLOC_TB_SIZE];
spinlock_t lg_prealloc_lock;
};
struct ext4_allocation_context {
struct inode *ac_inode;
struct super_block *ac_sb;
/* original request */
struct ext4_free_extent ac_o_ex;
/* goal request (normalized ac_o_ex) */
struct ext4_free_extent ac_g_ex;
/* the best found extent */
struct ext4_free_extent ac_b_ex;
/* copy of the best found extent taken before preallocation efforts */
struct ext4_free_extent ac_f_ex;
/*
* goal len can change in CR1.5, so save the original len. This is
* used while adjusting the PA window and for accounting.
*/
ext4_grpblk_t ac_orig_goal_len;
__u32 ac_groups_considered;
__u32 ac_flags; /* allocation hints */
__u16 ac_groups_scanned;
__u16 ac_groups_linear_remaining;
__u16 ac_found;
__u16 ac_cX_found[EXT4_MB_NUM_CRS];
__u16 ac_tail;
__u16 ac_buddy;
__u8 ac_status;
__u8 ac_criteria;
__u8 ac_2order; /* if request is to allocate 2^N blocks and
* N > 0, the field stores N, otherwise 0 */
__u8 ac_op; /* operation, for history only */
struct page *ac_bitmap_page;
struct page *ac_buddy_page;
struct ext4_prealloc_space *ac_pa;
struct ext4_locality_group *ac_lg;
};
#define AC_STATUS_CONTINUE 1
#define AC_STATUS_FOUND 2
#define AC_STATUS_BREAK 3
struct ext4_buddy {
struct page *bd_buddy_page;
void *bd_buddy;
struct page *bd_bitmap_page;
void *bd_bitmap;
struct ext4_group_info *bd_info;
struct super_block *bd_sb;
__u16 bd_blkbits;
ext4_group_t bd_group;
};
static inline ext4_fsblk_t ext4_grp_offs_to_block(struct super_block *sb,
struct ext4_free_extent *fex)
{
return ext4_group_first_block_no(sb, fex->fe_group) +
(fex->fe_start << EXT4_SB(sb)->s_cluster_bits);
}
typedef int (*ext4_mballoc_query_range_fn)(
struct super_block *sb,
ext4_group_t agno,
ext4_grpblk_t start,
ext4_grpblk_t len,
void *priv);
int
ext4_mballoc_query_range(
struct super_block *sb,
ext4_group_t agno,
ext4_grpblk_t start,
ext4_grpblk_t end,
ext4_mballoc_query_range_fn formatter,
void *priv);
#endif