[PATCH 10/28] mm: memory reserve management

Peter Zijlstra
2008-02-20T15:18:36Z

[-- Attachment #1: mm-reserve.patch --]
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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.

It should also allow for a Banker's algorithm replacement of __GFP_NOFAIL.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/linux/reserve.h | 54 ++++++
mm/Makefile | 2
mm/reserve.c | 429 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 484 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-$(CONFIG_PROC_PAGE_MONITOR) += pagewalk.o
obj-$(CONFIG_BOUNCE) += bounce.o
Index: linux-2.6/mm/reserve.c
===================================================================
--- /dev/null
+++ linux-2.6/mm/reserve.c
@@ -0,0 +1,429 @@
+/*
+ * 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",
+ .lock = __SPIN_LOCK_UNLOCKED(mem_reserve_root.lock),
+};
+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;
+ spin_lock_init(&res->lock);
+
+ 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);

--