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    Subject[PATCH 11/33] mm: memory reserve management
    Generic reserve management code. 

    It provides methods to reserve and charge. Upon this, generic alloc/free style
    reserve pools could be build, which could fully replace mempool_t
    functionality.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    include/linux/reserve.h | 54 +++++
    mm/Makefile | 2
    mm/reserve.c | 436 ++++++++++++++++++++++++++++++++++++++++++++++++
    3 files changed, 491 insertions(+), 1 deletion(-)

    Index: linux-2.6/include/linux/reserve.h
    ===================================================================
    --- /dev/null
    +++ linux-2.6/include/linux/reserve.h
    @@ -0,0 +1,54 @@
    +/*
    + * Memory reserve management.
    + *
    + * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
    + *
    + * This file contains the public data structure and API definitions.
    + */
    +
    +#ifndef _LINUX_RESERVE_H
    +#define _LINUX_RESERVE_H
    +
    +#include <linux/list.h>
    +#include <linux/spinlock.h>
    +
    +struct mem_reserve {
    + struct mem_reserve *parent;
    + struct list_head children;
    + struct list_head siblings;
    +
    + const char *name;
    +
    + long pages;
    + long limit;
    + long usage;
    + spinlock_t lock; /* protects limit and usage */
    +};
    +
    +extern struct mem_reserve mem_reserve_root;
    +
    +void mem_reserve_init(struct mem_reserve *res, const char *name,
    + struct mem_reserve *parent);
    +int mem_reserve_connect(struct mem_reserve *new_child,
    + struct mem_reserve *node);
    +int mem_reserve_disconnect(struct mem_reserve *node);
    +
    +int mem_reserve_pages_set(struct mem_reserve *res, long pages);
    +int mem_reserve_pages_add(struct mem_reserve *res, long pages);
    +int mem_reserve_pages_charge(struct mem_reserve *res, long pages,
    + int overcommit);
    +
    +int mem_reserve_kmalloc_set(struct mem_reserve *res, long bytes);
    +int mem_reserve_kmalloc_charge(struct mem_reserve *res, long bytes,
    + int overcommit);
    +
    +struct kmem_cache;
    +
    +int mem_reserve_kmem_cache_set(struct mem_reserve *res,
    + struct kmem_cache *s,
    + int objects);
    +int mem_reserve_kmem_cache_charge(struct mem_reserve *res,
    + long objs,
    + int overcommit);
    +
    +#endif /* _LINUX_RESERVE_H */
    Index: linux-2.6/mm/Makefile
    ===================================================================
    --- linux-2.6.orig/mm/Makefile
    +++ linux-2.6/mm/Makefile
    @@ -11,7 +11,7 @@ obj-y := bootmem.o filemap.o mempool.o
    page_alloc.o page-writeback.o pdflush.o \
    readahead.o swap.o truncate.o vmscan.o \
    prio_tree.o util.o mmzone.o vmstat.o backing-dev.o \
    - page_isolation.o $(mmu-y)
    + page_isolation.o reserve.o $(mmu-y)

    obj-$(CONFIG_BOUNCE) += bounce.o
    obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o thrash.o
    Index: linux-2.6/mm/reserve.c
    ===================================================================
    --- /dev/null
    +++ linux-2.6/mm/reserve.c
    @@ -0,0 +1,436 @@
    +/*
    + * Memory reserve management.
    + *
    + * Copyright (C) 2007, Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
    + *
    + * Description:
    + *
    + * Manage a set of memory reserves.
    + *
    + * A memory reserve is a reserve for a specified number of object of specified
    + * size. Since memory is managed in pages, this reserve demand is then
    + * translated into a page unit.
    + *
    + * So each reserve has a specified object limit, an object usage count and a
    + * number of pages required to back these objects.
    + *
    + * Usage is charged against a reserve, if the charge fails, the resource must
    + * not be allocated/used.
    + *
    + * The reserves are managed in a tree, and the resource demands (pages and
    + * limit) are propagated up the tree. Obviously the object limit will be
    + * meaningless as soon as the unit starts mixing, but the required page reserve
    + * (being of one unit) is still valid at the root.
    + *
    + * It is the page demand of the root node that is used to set the global
    + * reserve (adjust_memalloc_reserve() which sets zone->pages_emerg).
    + *
    + * As long as a subtree has the same usage unit, an aggregate node can be used
    + * to charge against, instead of the leaf nodes. However, do be consistent with
    + * who is charged, resource usage is not propagated up the tree (for
    + * performance reasons).
    + */
    +
    +#include <linux/reserve.h>
    +#include <linux/mutex.h>
    +#include <linux/mmzone.h>
    +#include <linux/log2.h>
    +#include <linux/proc_fs.h>
    +#include <linux/seq_file.h>
    +#include <linux/module.h>
    +#include <linux/slab.h>
    +
    +static DEFINE_MUTEX(mem_reserve_mutex);
    +
    +/**
    + * @mem_reserve_root - the global reserve root
    + *
    + * The global reserve is empty, and has no limit unit, it merely
    + * acts as an aggregation point for reserves and an interface to
    + * adjust_memalloc_reserve().
    + */
    +struct mem_reserve mem_reserve_root = {
    + .children = LIST_HEAD_INIT(mem_reserve_root.children),
    + .siblings = LIST_HEAD_INIT(mem_reserve_root.siblings),
    + .name = "total reserve",
    +};
    +
    +EXPORT_SYMBOL_GPL(mem_reserve_root);
    +
    +/**
    + * mem_reserve_init - initialize a memory reserve object
    + * @res - the new reserve object
    + * @name - a name for this reserve
    + */
    +void mem_reserve_init(struct mem_reserve *res, const char *name,
    + struct mem_reserve *parent)
    +{
    + memset(res, 0, sizeof(*res));
    + INIT_LIST_HEAD(&res->children);
    + INIT_LIST_HEAD(&res->siblings);
    + res->name = name;
    +
    + if (parent)
    + mem_reserve_connect(res, parent);
    +}
    +
    +EXPORT_SYMBOL_GPL(mem_reserve_init);
    +
    +/*
    + * propagate the pages and limit changes up the tree.
    + */
    +static void __calc_reserve(struct mem_reserve *res, long pages, long limit)
    +{
    + unsigned long flags;
    +
    + for ( ; res; res = res->parent) {
    + res->pages += pages;
    +
    + if (limit) {
    + spin_lock_irqsave(&res->lock, flags);
    + res->limit += limit;
    + spin_unlock_irqrestore(&res->lock, flags);
    + }
    + }
    +}
    +
    +/**
    + * __mem_reserve_add - primitive to change the size of a reserve
    + * @res - reserve to change
    + * @pages - page delta
    + * @limit - usage limit delta
    + *
    + * Returns -ENOMEM when a size increase is not possible atm.
    + */
    +static int __mem_reserve_add(struct mem_reserve *res, long pages, long limit)
    +{
    + int ret = 0;
    + long reserve;
    +
    + reserve = mem_reserve_root.pages;
    + __calc_reserve(res, pages, 0);
    + reserve = mem_reserve_root.pages - reserve;
    +
    + if (reserve) {
    + ret = adjust_memalloc_reserve(reserve);
    + if (ret)
    + __calc_reserve(res, -pages, 0);
    + }
    +
    + if (!ret)
    + __calc_reserve(res, 0, limit);
    +
    + return ret;
    +}
    +
    +/**
    + * __mem_reserve_charge - primitive to charge object usage to a reserve
    + * @res - reserve to charge
    + * @charge - size of the charge
    + * @overcommit - allow despite of limit (use with caution!)
    + *
    + * Returns non-zero on success, zero on failure.
    + */
    +static
    +int __mem_reserve_charge(struct mem_reserve *res, long charge, int overcommit)
    +{
    + unsigned long flags;
    + int ret = 0;
    +
    + spin_lock_irqsave(&res->lock, flags);
    + if (charge < 0 || res->usage + charge < res->limit || overcommit) {
    + res->usage += charge;
    + if (unlikely(res->usage < 0))
    + res->usage = 0;
    + ret = 1;
    + }
    + spin_unlock_irqrestore(&res->lock, flags);
    +
    + return ret;
    +}
    +
    +/**
    + * mem_reserve_connect - connect a reserve to another in a child-parent relation
    + * @new_child - the reserve node to connect (child)
    + * @node - the reserve node to connect to (parent)
    + *
    + * Returns -ENOMEM when the new connection would increase the reserve (parent
    + * is connected to mem_reserve_root) and there is no memory to do so.
    + *
    + * The child is _NOT_ connected on error.
    + */
    +int mem_reserve_connect(struct mem_reserve *new_child, struct mem_reserve *node)
    +{
    + int ret;
    +
    + WARN_ON(!new_child->name);
    +
    + mutex_lock(&mem_reserve_mutex);
    + new_child->parent = node;
    + list_add(&new_child->siblings, &node->children);
    + ret = __mem_reserve_add(node, new_child->pages, new_child->limit);
    + if (ret) {
    + new_child->parent = NULL;
    + list_del_init(&new_child->siblings);
    + }
    + mutex_unlock(&mem_reserve_mutex);
    +
    + return ret;
    +}
    +
    +EXPORT_SYMBOL_GPL(mem_reserve_connect);
    +
    +/**
    + * mem_reserve_disconnect - sever a nodes connection to the reserve tree
    + * @node - the node to disconnect
    + *
    + * Could, in theory, return -ENOMEM, but since disconnecting a node _should_
    + * only decrease the reserves that _should_ not happen.
    + */
    +int mem_reserve_disconnect(struct mem_reserve *node)
    +{
    + int ret;
    +
    + BUG_ON(!node->parent);
    +
    + mutex_lock(&mem_reserve_mutex);
    + ret = __mem_reserve_add(node->parent, -node->pages, -node->limit);
    + if (!ret) {
    + node->parent = NULL;
    + list_del_init(&node->siblings);
    + }
    + mutex_unlock(&mem_reserve_mutex);
    +
    + return ret;
    +}
    +
    +EXPORT_SYMBOL_GPL(mem_reserve_disconnect);
    +
    +#ifdef CONFIG_PROC_FS
    +
    +/*
    + * Simple output of the reserve tree in: /proc/reserve_info
    + * Example:
    + *
    + * localhost ~ # cat /proc/reserve_info
    + * total reserve 8156K (0/544817)
    + * total network reserve 8156K (0/544817)
    + * network TX reserve 196K (0/49)
    + * protocol TX pages 196K (0/49)
    + * network RX reserve 7960K (0/544768)
    + * IPv6 route cache 1372K (0/4096)
    + * IPv4 route cache 5468K (0/16384)
    + * SKB data reserve 1120K (0/524288)
    + * IPv6 fragment cache 560K (0/262144)
    + * IPv4 fragment cache 560K (0/262144)
    + */
    +
    +static void mem_reserve_show_item(struct seq_file *m, struct mem_reserve *res,
    + int nesting)
    +{
    + int i;
    + struct mem_reserve *child;
    +
    + for (i = 0; i < nesting; i++)
    + seq_puts(m, " ");
    +
    + seq_printf(m, "%-30s %ldK (%ld/%ld)\n",
    + res->name, res->pages << (PAGE_SHIFT - 10),
    + res->usage, res->limit);
    +
    + list_for_each_entry(child, &res->children, siblings)
    + mem_reserve_show_item(m, child, nesting+1);
    +}
    +
    +static int mem_reserve_show(struct seq_file *m, void *v)
    +{
    + mutex_lock(&mem_reserve_mutex);
    + mem_reserve_show_item(m, &mem_reserve_root, 0);
    + mutex_unlock(&mem_reserve_mutex);
    +
    + return 0;
    +}
    +
    +static int mem_reserve_open(struct inode *inode, struct file *file)
    +{
    + return single_open(file, mem_reserve_show, NULL);
    +}
    +
    +static const struct file_operations mem_reserve_opterations = {
    + .open = mem_reserve_open,
    + .read = seq_read,
    + .llseek = seq_lseek,
    + .release = single_release,
    +};
    +
    +static __init int mem_reserve_proc_init(void)
    +{
    + struct proc_dir_entry *entry;
    +
    + entry = create_proc_entry("reserve_info", S_IRUSR, NULL);
    + if (entry)
    + entry->proc_fops = &mem_reserve_opterations;
    +
    + return 0;
    +}
    +
    +__initcall(mem_reserve_proc_init);
    +
    +#endif
    +
    +/*
    + * alloc_page helpers
    + */
    +
    +/**
    + * mem_reserve_pages_set - set reserves size in pages
    + * @res - reserve to set
    + * @pages - size in pages to set it to
    + *
    + * Returns -ENOMEM when it fails to set the reserve. On failure the old size
    + * is preserved.
    + */
    +int mem_reserve_pages_set(struct mem_reserve *res, long pages)
    +{
    + int ret;
    +
    + mutex_lock(&mem_reserve_mutex);
    + pages -= res->pages;
    + ret = __mem_reserve_add(res, pages, pages);
    + mutex_unlock(&mem_reserve_mutex);
    +
    + return ret;
    +}
    +
    +EXPORT_SYMBOL_GPL(mem_reserve_pages_set);
    +
    +/**
    + * mem_reserve_pages_add - change the size in a relative way
    + * @res - reserve to change
    + * @pages - number of pages to add (or subtract when negative)
    + *
    + * Similar to mem_reserve_pages_set, except that the argument is relative instead
    + * of absolute.
    + *
    + * Returns -ENOMEM when it fails to increase.
    + */
    +int mem_reserve_pages_add(struct mem_reserve *res, long pages)
    +{
    + int ret;
    +
    + mutex_lock(&mem_reserve_mutex);
    + ret = __mem_reserve_add(res, pages, pages);
    + mutex_unlock(&mem_reserve_mutex);
    +
    + return ret;
    +}
    +
    +/**
    + * mem_reserve_pages_charge - charge page usage to a reserve
    + * @res - reserve to charge
    + * @pages - size to charge
    + * @overcommit - disregard the usage limit (use with caution!)
    + *
    + * Returns non-zero on success.
    + */
    +int mem_reserve_pages_charge(struct mem_reserve *res, long pages, int overcommit)
    +{
    + return __mem_reserve_charge(res, pages, overcommit);
    +}
    +
    +EXPORT_SYMBOL_GPL(mem_reserve_pages_charge);
    +
    +/*
    + * kmalloc helpers
    + */
    +
    +/**
    + * mem_reserve_kmalloc_set - set this reserve to bytes worth of kmalloc
    + * @res - reserve to change
    + * @bytes - size in bytes to reserve
    + *
    + * Returns -ENOMEM on failure.
    + */
    +int mem_reserve_kmalloc_set(struct mem_reserve *res, long bytes)
    +{
    + int ret;
    + long pages;
    +
    + mutex_lock(&mem_reserve_mutex);
    + pages = kestimate(GFP_ATOMIC, bytes);
    + pages -= res->pages;
    + bytes -= res->limit;
    + ret = __mem_reserve_add(res, pages, bytes);
    + mutex_unlock(&mem_reserve_mutex);
    +
    + return ret;
    +}
    +
    +EXPORT_SYMBOL_GPL(mem_reserve_kmalloc_set);
    +
    +/**
    + * mem_reserve_kmalloc_charge - charge bytes to a reserve
    + * @res - reserve to charge
    + * @bytes - bytes to charge
    + * @overcommit - disregard the usage limit (use with caution!)
    + *
    + * Returns non-zero on success.
    + */
    +int mem_reserve_kmalloc_charge(struct mem_reserve *res, long bytes,
    + int overcommit)
    +{
    + if (bytes < 0)
    + bytes = -roundup_pow_of_two(-bytes);
    + else
    + bytes = roundup_pow_of_two(bytes);
    +
    + return __mem_reserve_charge(res, bytes, overcommit);
    +}
    +
    +EXPORT_SYMBOL_GPL(mem_reserve_kmalloc_charge);
    +
    +/*
    + * kmem_cache helpers
    + */
    +
    +/**
    + * mem_reserve_kmem_cache_set - set reserve to @objects worth of kmem_cache_alloc of @s
    + * @res - reserve to set
    + * @s - kmem_cache to reserve from
    + * @objects - number of objects to reserve
    + *
    + * Returns -ENOMEM on failure.
    + */
    +int mem_reserve_kmem_cache_set(struct mem_reserve *res, struct kmem_cache *s,
    + int objects)
    +{
    + int ret;
    + long pages;
    +
    + mutex_lock(&mem_reserve_mutex);
    + pages = kmem_estimate_pages(s, GFP_ATOMIC, objects);
    + pages -= res->pages;
    + objects -= res->limit;
    + ret = __mem_reserve_add(res, pages, objects);
    + mutex_unlock(&mem_reserve_mutex);
    +
    + return ret;
    +}
    +
    +EXPORT_SYMBOL_GPL(mem_reserve_kmem_cache_set);
    +
    +/**
    + * mem_reserve_kmem_cache_charge - charge (or uncharge) usage of objs
    + * @res - reserve to charge
    + * @objs - objects to charge for
    + * @overcommit - disregard the usage limit (use with caution!)
    + *
    + * Returns non-zero on success.
    + */
    +int mem_reserve_kmem_cache_charge(struct mem_reserve *res, long objs,
    + int overcommit)
    +{
    + return __mem_reserve_charge(res, objs, overcommit);
    +}
    +
    +EXPORT_SYMBOL_GPL(mem_reserve_kmem_cache_charge);
    --

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