drivers/staging/ramzswap/ramzswap_drv.h

   1 /*
   2  * Compressed RAM based swap device
   3  *
   4  * Copyright (C) 2008, 2009  Nitin Gupta
   5  *
   6  * This code is released using a dual license strategy: BSD/GPL
   7  * You can choose the licence that better fits your requirements.
   8  *
   9  * Released under the terms of 3-clause BSD License
  10  * Released under the terms of GNU General Public License Version 2.0
  11  *
  12  * Project home: http://compcache.googlecode.com
  13  */
  14
  15 #ifndef _RAMZSWAP_DRV_H_
  16 #define _RAMZSWAP_DRV_H_
  17
  18 #include "ramzswap_ioctl.h"
  19 #include "xvmalloc.h"
  20
  21 /*
  22  * Some arbitrary value. This is just to catch
  23  * invalid value for num_devices module parameter.
  24  */
  25 static const unsigned max_num_devices = 32;
  26
  27 /*
  28  * Stored at beginning of each compressed object.
  29  *
  30  * It stores back-reference to table entry which points to this
  31  * object. This is required to support memory defragmentation or
  32  * migrating compressed pages to backing swap disk.
  33  */
  34 struct zobj_header {
  35 #if 0
  36         u32 table_idx;
  37 #endif
  38 };
  39
  40 /*-- Configurable parameters */
  41
  42 /* Default ramzswap disk size: 25% of total RAM */
  43 static const unsigned default_disksize_perc_ram = 25;
  44 static const unsigned default_memlimit_perc_ram = 15;
  45
  46 /*
  47  * Max compressed page size when backing device is provided.
  48  * Pages that compress to size greater than this are sent to
  49  * physical swap disk.
  50  */
  51 static const unsigned max_zpage_size_bdev = PAGE_SIZE / 2;
  52
  53 /*
  54  * Max compressed page size when there is no backing dev.
  55  * Pages that compress to size greater than this are stored
  56  * uncompressed in memory.
  57  */
  58 static const unsigned max_zpage_size_nobdev = PAGE_SIZE / 4 * 3;
  59
  60 /*
  61  * NOTE: max_zpage_size_{bdev,nobdev} sizes must be
  62  * less than or equal to:
  63  *   XV_MAX_ALLOC_SIZE - sizeof(struct zobj_header)
  64  * since otherwise xv_malloc would always return failure.
  65  */
  66
  67 /*-- End of configurable params */
  68
  69 #define SECTOR_SHIFT            9
  70 #define SECTOR_SIZE             (1 << SECTOR_SHIFT)
  71 #define SECTORS_PER_PAGE_SHIFT  (PAGE_SHIFT - SECTOR_SHIFT)
  72 #define SECTORS_PER_PAGE        (1 << SECTORS_PER_PAGE_SHIFT)
  73
  74 /* Debugging and Stats */
  75 #if defined(CONFIG_RAMZSWAP_STATS)
  76 #define stat_inc(stat)  ((stat)++)
  77 #define stat_dec(stat)  ((stat)--)
  78 #else
  79 #define stat_inc(x)
  80 #define stat_dec(x)
  81 #endif
  82
  83 /* Flags for ramzswap pages (table[page_no].flags) */
  84 enum rzs_pageflags {
  85         /* Page is stored uncompressed */
  86         RZS_UNCOMPRESSED,
  87
  88         /* Page consists entirely of zeros */
  89         RZS_ZERO,
  90
  91         __NR_RZS_PAGEFLAGS,
  92 };
  93
  94 /*-- Data structures */
  95
  96 /*
  97  * Allocated for each swap slot, indexed by page no.
  98  * These table entries must fit exactly in a page.
  99  */
 100 struct table {
 101         struct page *page;
 102         u16 offset;
 103         u8 count;       /* object ref count (not yet used) */
 104         u8 flags;
 105 } __attribute__((aligned(4)));;
 106
 107 /*
 108  * Swap extent information in case backing swap is a regular
 109  * file. These extent entries must fit exactly in a page.
 110  */
 111 struct ramzswap_backing_extent {
 112         pgoff_t phy_pagenum;
 113         pgoff_t num_pages;
 114 } __attribute__((aligned(4)));
 115
 116 struct ramzswap_stats {
 117         /* basic stats */
 118         size_t compr_size;      /* compressed size of pages stored -
 119                                  * needed to enforce memlimit */
 120         /* more stats */
 121 #if defined(CONFIG_RAMZSWAP_STATS)
 122         u64 num_reads;          /* failed + successful */
 123         u64 num_writes;         /* --do-- */
 124         u64 failed_reads;       /* can happen when memory is too low */
 125         u64 failed_writes;      /* should NEVER! happen */
 126         u64 invalid_io;         /* non-swap I/O requests */
 127         u32 pages_zero;         /* no. of zero filled pages */
 128         u32 pages_stored;       /* no. of pages currently stored */
 129         u32 good_compress;      /* % of pages with compression ratio<=50% */
 130         u32 pages_expand;       /* % of incompressible pages */
 131         u64 bdev_num_reads;     /* no. of reads on backing dev */
 132         u64 bdev_num_writes;    /* no. of writes on backing dev */
 133 #endif
 134 };
 135
 136 struct ramzswap {
 137         struct xv_pool *mem_pool;
 138         void *compress_workmem;
 139         void *compress_buffer;
 140         struct table *table;
 141         struct mutex lock;
 142         struct request_queue *queue;
 143         struct gendisk *disk;
 144         int init_done;
 145         /*
 146          * This is limit on compressed data size (stats.compr_size)
 147          * Its applicable only when backing swap device is present.
 148          */
 149         size_t memlimit;        /* bytes */
 150         /*
 151          * This is limit on amount of *uncompressed* worth of data
 152          * we can hold. When backing swap device is provided, it is
 153          * set equal to device size.
 154          */
 155         size_t disksize;        /* bytes */
 156
 157         struct ramzswap_stats stats;
 158
 159         /* backing swap device info */
 160         struct ramzswap_backing_extent *curr_extent;
 161         struct list_head backing_swap_extent_list;
 162         unsigned long num_extents;
 163         char backing_swap_name[MAX_SWAP_NAME_LEN];
 164         struct block_device *backing_swap;
 165         struct file *swap_file;
 166 };
 167
 168 /*-- */
 169
 170 #endif
 171