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92967471b6
Currently, the zram table is protected by zram->lock but it's rather coarse-grained lock and it makes hard for scalibility. Let's use own rwlock instead of depending on zram->lock. This patch adds new locking so obviously, it would make slow but this patch is just prepartion for removing coarse-grained rw_semaphore(ie, zram->lock) which is hurdle about zram scalability. Final patch in this patchset series will remove the lock from read-path and change rw_semaphore with mutex in write path. With bonus, we could drop pending slot free mess in next patch. Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Nitin Gupta <ngupta@vflare.org> Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Jerome Marchand <jmarchan@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
121 lines
3.2 KiB
C
121 lines
3.2 KiB
C
/*
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* Compressed RAM block device
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*
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* Copyright (C) 2008, 2009, 2010 Nitin Gupta
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* 2012, 2013 Minchan Kim
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*
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* This code is released using a dual license strategy: BSD/GPL
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* You can choose the licence that better fits your requirements.
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*
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* Released under the terms of 3-clause BSD License
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* Released under the terms of GNU General Public License Version 2.0
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*
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*/
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#ifndef _ZRAM_DRV_H_
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#define _ZRAM_DRV_H_
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#include <linux/spinlock.h>
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#include <linux/mutex.h>
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#include <linux/zsmalloc.h>
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/*
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* Some arbitrary value. This is just to catch
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* invalid value for num_devices module parameter.
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*/
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static const unsigned max_num_devices = 32;
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/*-- Configurable parameters */
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/*
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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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*/
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static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
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/*
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* NOTE: max_zpage_size must be less than or equal to:
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* ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would
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* always return failure.
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*/
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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 ZRAM_LOGICAL_BLOCK_SHIFT 12
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#define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
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#define ZRAM_SECTOR_PER_LOGICAL_BLOCK \
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(1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
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/* Flags for zram pages (table[page_no].flags) */
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enum zram_pageflags {
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/* Page consists entirely of zeros */
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ZRAM_ZERO,
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__NR_ZRAM_PAGEFLAGS,
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};
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/*-- Data structures */
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/* Allocated for each disk page */
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struct table {
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unsigned long handle;
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u16 size; /* object size (excluding header) */
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u8 count; /* object ref count (not yet used) */
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u8 flags;
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} __aligned(4);
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struct zram_stats {
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atomic64_t compr_size; /* compressed size of pages stored */
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atomic64_t num_reads; /* failed + successful */
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atomic64_t num_writes; /* --do-- */
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atomic64_t failed_reads; /* should NEVER! happen */
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atomic64_t failed_writes; /* can happen when memory is too low */
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atomic64_t invalid_io; /* non-page-aligned I/O requests */
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atomic64_t notify_free; /* no. of swap slot free notifications */
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atomic_t pages_zero; /* no. of zero filled pages */
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atomic_t pages_stored; /* no. of pages currently stored */
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atomic_t good_compress; /* % of pages with compression ratio<=50% */
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atomic_t bad_compress; /* % of pages with compression ratio>=75% */
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};
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struct zram_meta {
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rwlock_t tb_lock; /* protect table */
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void *compress_workmem;
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void *compress_buffer;
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struct table *table;
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struct zs_pool *mem_pool;
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};
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struct zram_slot_free {
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unsigned long index;
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struct zram_slot_free *next;
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};
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struct zram {
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struct zram_meta *meta;
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struct rw_semaphore lock; /* protect compression buffers,
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* reads and writes
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*/
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struct work_struct free_work; /* handle pending free request */
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struct zram_slot_free *slot_free_rq; /* list head of free request */
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struct request_queue *queue;
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struct gendisk *disk;
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int init_done;
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/* Prevent concurrent execution of device init, reset and R/W request */
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struct rw_semaphore init_lock;
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/*
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* This is the limit on amount of *uncompressed* worth of data
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* we can store in a disk.
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*/
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u64 disksize; /* bytes */
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spinlock_t slot_free_lock;
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struct zram_stats stats;
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};
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#endif
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