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* Compressed RAM based swap device
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* Copyright (C) 2008, 2009 Nitin Gupta
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* This RAM based block device acts as swap disk.
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* Pages swapped to this device are compressed and
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* Released under the terms of GNU General Public License Version 2.0
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* Project home: http://compcache.googlecode.com
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* Stored at beginning of each compressed object.
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* It stores back-reference to table entry which points to this
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* object. This is required to support memory defragmentation or
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* migrating compressed pages to backing swap disk.
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/*-- Configurable parameters */
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/* Default ramzswap disk size: 25% of total RAM */
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#define DEFAULT_DISKSIZE_PERC_RAM 25
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#define DEFAULT_MEMLIMIT_PERC_RAM 15
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* Max compressed page size when backing device is provided.
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* Pages that compress to size greater than this are sent to
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#define MAX_CPAGE_SIZE_BDEV (PAGE_SIZE / 2)
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* Max compressed page size when there is no backing dev.
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* Pages that compress to size greater than this are stored
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* uncompressed in memory.
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#define MAX_CPAGE_SIZE_NOBDEV (PAGE_SIZE / 4 * 3)
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* NOTE: MAX_CPAGE_SIZE_{BDEV,NOBDEV} sizes must be
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* less than or equal to:
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* XV_MAX_ALLOC_SIZE - sizeof(struct zobj_header)
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* since otherwise xvMalloc would always return failure.
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/*-- End of configurable params */
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#define SECTOR_SHIFT 9
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#define SECTOR_SIZE (1 << SECTOR_SHIFT)
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#define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
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#define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT)
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#define C "ramzswap: "
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/* Debugging and Stats */
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#define NOP do { } while (0)
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#if defined(CONFIG_BLK_DEV_RAMZSWAP_STATS)
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#define stat_inc(stat) ((stat)++)
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#define stat_dec(stat) ((stat)--)
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#define stat_inc_if_less(stat, val1, val2) \
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((stat) += ((val1) < (val2) ? 1 : 0))
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#define stat_dec_if_less(stat, val1, val2) \
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((stat) -= ((val1) < (val2) ? 1 : 0))
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#define stat_inc(x) NOP
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#define stat_dec(x) NOP
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#define stat_inc_if_less(x, v1, v2) NOP
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#define stat_dec_if_less(x, v1, v2) NOP
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/* Flags for ramzswap pages (table[page_no].flags) */
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/* Page is stored uncompressed */
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/* Page consists entirely of zeros */
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/*-- Data structures */
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/* Indexed by page no. */
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u8 count; /* object ref count (not yet used) */
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struct xv_pool *mem_pool;
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void *compress_workmem;
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void *compress_buffer;
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struct gendisk *disk;
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* This is limit on compressed data size (stats.compr_size)
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* Its applicable only when backing swap device is present.
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size_t memlimit; /* bytes */
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* This is limit on amount of *uncompressed* worth of data
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* we can hold. When backing swap device is provided, it is
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* set equal to device size.
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size_t disksize; /* bytes */
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/* backing swap device info */
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struct block_device *backing_swap;
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struct file *swap_file;
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struct ramzswap_stats {
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size_t compr_size; /* compressed size of pages stored -
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* needed to enforce memlimit */
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u64 num_reads; /* failed + successful */
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u64 num_writes; /* --do-- */
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u64 failed_reads; /* can happen when memory is too low */
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u64 failed_writes; /* should NEVER! happen */
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u64 invalid_io; /* non-swap I/O requests */
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u64 pages_discard; /* no. of pages freed by discard callback */
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u32 pages_zero; /* no. of zero filled pages */
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u32 pages_stored; /* no. of pages currently stored */
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u32 good_compress; /* no. of pages with compression ratio<=50% */
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u32 pages_expand; /* no. of incompressible pages */
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u64 bdev_num_reads; /* no. of reads on backing dev */
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u64 bdev_num_writes; /* no. of writes on backing dev */
added
removed
ubuntu/compcache/ramzswap.h
