drivers/staging/ramzswap/ramzswap_drv.h

   1 /*
   2  * Compressed RAM based swap device
   3  *
   4  * Copyright (C) 2008, 2009, 2010  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 <linux/spinlock.h>
  19 #include <linux/mutex.h>
  20
  21 #include "ramzswap_ioctl.h"
  22 #include "xvmalloc.h"
  23
  24 /*
  25  * Some arbitrary value. This is just to catch
  26  * invalid value for num_devices module parameter.
  27  */
  28 static const unsigned max_num_devices = 32;
  29
  30 /*
  31  * Stored at beginning of each compressed object.
  32  *
  33  * It stores back-reference to table entry which points to this
  34  * object. This is required to support memory defragmentation.
  35  */
  36 struct zobj_header {
  37 #if 0
  38         u32 table_idx;
  39 #endif
  40 };
  41
  42 /*-- Configurable parameters */
  43
  44 /* Default ramzswap disk size: 25% of total RAM */
  45 static const unsigned default_disksize_perc_ram = 25;
  46
  47 /*
  48  * Pages that compress to size greater than this are stored
  49  * uncompressed in memory.
  50  */
  51 static const unsigned max_zpage_size = PAGE_SIZE / 4 * 3;
  52
  53 /*
  54  * NOTE: max_zpage_size must be less than or equal to:
  55  *   XV_MAX_ALLOC_SIZE - sizeof(struct zobj_header)
  56  * otherwise, xv_malloc() would always return failure.
  57  */
  58
  59 /*-- End of configurable params */
  60
  61 #define SECTOR_SHIFT            9
  62 #define SECTOR_SIZE             (1 << SECTOR_SHIFT)
  63 #define SECTORS_PER_PAGE_SHIFT  (PAGE_SHIFT - SECTOR_SHIFT)
  64 #define SECTORS_PER_PAGE        (1 << SECTORS_PER_PAGE_SHIFT)
  65
  66 /* Flags for ramzswap pages (table[page_no].flags) */
  67 enum rzs_pageflags {
  68         /* Page is stored uncompressed */
  69         RZS_UNCOMPRESSED,
  70
  71         /* Page consists entirely of zeros */
  72         RZS_ZERO,
  73
  74         __NR_RZS_PAGEFLAGS,
  75 };
  76
  77 /*-- Data structures */
  78
  79 /*
  80  * Allocated for each swap slot, indexed by page no.
  81  * These table entries must fit exactly in a page.
  82  */
  83 struct table {
  84         struct page *page;
  85         u16 offset;
  86         u8 count;       /* object ref count (not yet used) */
  87         u8 flags;
  88 } __attribute__((aligned(4)));
  89
  90 struct ramzswap_stats {
  91         /* basic stats */
  92         size_t compr_size;      /* compressed size of pages stored -
  93                                  * needed to enforce memlimit */
  94         /* more stats */
  95 #if defined(CONFIG_RAMZSWAP_STATS)
  96         u64 num_reads;          /* failed + successful */
  97         u64 num_writes;         /* --do-- */
  98         u64 failed_reads;       /* should NEVER! happen */
  99         u64 failed_writes;      /* can happen when memory is too low */
 100         u64 invalid_io;         /* non-swap I/O requests */
 101         u64 notify_free;        /* no. of swap slot free notifications */
 102         u32 pages_zero;         /* no. of zero filled pages */
 103         u32 pages_stored;       /* no. of pages currently stored */
 104         u32 good_compress;      /* % of pages with compression ratio<=50% */
 105         u32 pages_expand;       /* % of incompressible pages */
 106 #endif
 107 };
 108
 109 struct ramzswap {
 110         struct xv_pool *mem_pool;
 111         void *compress_workmem;
 112         void *compress_buffer;
 113         struct table *table;
 114         spinlock_t stat64_lock; /* protect 64-bit stats */
 115         struct mutex lock;      /* protect compression buffers against
 116                                  * concurrent writes */
 117         struct request_queue *queue;
 118         struct gendisk *disk;
 119         int init_done;
 120         /*
 121          * This is limit on amount of *uncompressed* worth of data
 122          * we can hold. When backing swap device is provided, it is
 123          * set equal to device size.
 124          */
 125         size_t disksize;        /* bytes */
 126
 127         struct ramzswap_stats stats;
 128 };
 129
 130 /*-- */
 131
 132 /* Debugging and Stats */
 133 #if defined(CONFIG_RAMZSWAP_STATS)
 134 static void rzs_stat_inc(u32 *v)
 135 {
 136         *v = *v + 1;
 137 }
 138
 139 static void rzs_stat_dec(u32 *v)
 140 {
 141         *v = *v - 1;
 142 }
 143
 144 static void rzs_stat64_inc(struct ramzswap *rzs, u64 *v)
 145 {
 146         spin_lock(&rzs->stat64_lock);
 147         *v = *v + 1;
 148         spin_unlock(&rzs->stat64_lock);
 149 }
 150
 151 static u64 rzs_stat64_read(struct ramzswap *rzs, u64 *v)
 152 {
 153         u64 val;
 154
 155         spin_lock(&rzs->stat64_lock);
 156         val = *v;
 157         spin_unlock(&rzs->stat64_lock);
 158
 159         return val;
 160 }
 161 #else
 162 #define rzs_stat_inc(v)
 163 #define rzs_stat_dec(v)
 164 #define rzs_stat64_inc(r, v)
 165 #define rzs_stat64_read(r, v)
 166 #endif /* CONFIG_RAMZSWAP_STATS */
 167
 168 #endif