linux-imx

/*

 * zswap.c - zswap driver file

 *

 * zswap is a backend for frontswap that takes pages that are in the process

 * of being swapped out and attempts to compress and store them in a

 * RAM-based memory pool.  This can result in a significant I/O reduction on

 * the swap device and, in the case where decompressing from RAM is faster

 * than reading from the swap device, can also improve workload performance.

 *

 * Copyright (C) 2012  Seth Jennings <sjenning@linux.vnet.ibm.com>

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version 2

 * of the License, or (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

*/

​

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

​

#include <linux/module.h>

#include <linux/cpu.h>

#include <linux/highmem.h>

#include <linux/slab.h>

#include <linux/spinlock.h>

#include <linux/types.h>

#include <linux/atomic.h>

#include <linux/frontswap.h>

#include <linux/rbtree.h>

#include <linux/swap.h>

#include <linux/crypto.h>

#include <linux/mempool.h>

#include <linux/zpool.h>

​

#include <linux/mm_types.h>

#include <linux/page-flags.h>

#include <linux/swapops.h>

#include <linux/writeback.h>

#include <linux/pagemap.h>

​

/*********************************

* statistics

**********************************/

/* Total bytes used by the compressed storage */

static u64 zswap_pool_total_size;

/* The number of compressed pages currently stored in zswap */

static atomic_t zswap_stored_pages = ATOMIC_INIT(0);

/* The number of same-value filled pages currently stored in zswap */

static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);

​

/*

 * The statistics below are not protected from concurrent access for

 * performance reasons so they may not be a 100% accurate.  However,

 * they do provide useful information on roughly how many times a

 * certain event is occurring.

*/

​

/* Pool limit was hit (see zswap_max_pool_percent) */

static u64 zswap_pool_limit_hit;