[PATCH 2/6] BC: beancounters core (API)

[Kirill Korotaev]

Core functionality and interfaces of BC:
find/create beancounter, initialization,
charge/uncharge of resource, core objects' declarations.

Basic structures:
 bc_resource_parm - resource description
 beancounter      - set of resources, id, lock


Signed-off-by: Pavel Emelianov <xemul@xxxxx>
Signed-off-by: Kirill Korotaev <dev@xxxxx>

---

include/bc/beancounter.h |  140 ++++++++++++++++++++++
init/main.c              |    4 
kernel/Makefile          |    1 
kernel/bc/Makefile       |    7 +
kernel/bc/beancounter.c  |  292 +++++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 444 insertions(+)

--- /dev/null	2006-07-18 14:52:43.075228448 +0400
+++ ./include/bc/beancounter.h	2006-08-21 13:14:01.000000000 +0400
@@ -0,0 +1,140 @@
+/*
+ *  include/bc/beancounter.h
+ *
+ *  Copyright (C) 2006 OpenVZ. SWsoft Inc
+ *
+ */
+
+#ifndef _LINUX_BEANCOUNTER_H
+#define _LINUX_BEANCOUNTER_H
+
+/*
+ *	Resource list.
+ */
+
+#define BC_RESOURCES	0
+
+struct bc_resource_parm {
+	unsigned long barrier;	/* A barrier over which resource allocations
+				 * are failed gracefully. e.g. if the amount
+				 * of consumed memory is over the barrier
+				 * further sbrk() or mmap() calls fail, the
+				 * existing processes are not killed.
+				 */
+	unsigned long limit;	/* hard resource limit */
+	unsigned long held;	/* consumed resources */
+	unsigned long maxheld;	/* maximum amount of consumed resources */
+	unsigned long minheld;	/* minumum amount of consumed resources */
+	unsigned long failcnt;	/* count of failed charges */
+};
+
+/*
+ * Kernel internal part.
+ */
+
+#ifdef __KERNEL__
+
+#include <linux/config.h>
+#include <linux/spinlock.h>
+#include <linux/list.h>
+#include <asm/atomic.h>
+
+#define BC_MAXVALUE	LONG_MAX
+
+/*
+ *	Resource management structures
+ * Serialization issues:
+ *   beancounter list management is protected via bc_hash_lock
+ *   task pointers are set only for current task and only once
+ *   refcount is managed atomically
+ *   value and limit comparison and change are protected by per-bc spinlock
+ */
+
+struct beancounter
+{
+	atomic_t		bc_refcount;
+	spinlock_t		bc_lock;
+	uid_t			bc_id;
+	struct hlist_node	hash;
+
+	/* resources statistics and settings */
+	struct bc_resource_parm	bc_parms[BC_RESOURCES];
+};
+
+enum severity { BC_BARRIER, BC_LIMIT, BC_FORCE };
+
+/* Flags passed to beancounter_findcreate() */
+#define BC_ALLOC		0x01 /* May allocate new one */
+#define BC_ALLOC_ATOMIC		0x02 /* Allocate with GFP_ATOMIC */
+
+#define BC_HASH_SIZE		256
+
+#ifdef CONFIG_BEANCOUNTERS
+extern struct hlist_head bc_hash[];
+extern spinlock_t bc_hash_lock;
+
+/*
+ * This function tunes minheld and maxheld values for a given
+ * resource when held value changes
+ */
+static inline void bc_adjust_held_minmax(struct beancounter *bc,
+		int resource)
+{
+	if (bc->bc_parms[resource].maxheld < bc->bc_parms[resource].held)
+		bc->bc_parms[resource].maxheld = bc->bc_parms[resource].held;
+	if (bc->bc_parms[resource].minheld > bc->bc_parms[resource].held)
+		bc->bc_parms[resource].minheld = bc->bc_parms[resource].held;
+}
+
+void bc_print_resource_warning(struct beancounter *bc, int res,
+		char *str, unsigned long val, unsigned long held);
+void bc_print_id(struct beancounter *bc, char *str, int size);
+
+int bc_charge_locked(struct beancounter *bc,
+		int res, unsigned long val, enum severity strict);
+int bc_charge(struct beancounter *bc,
+		int res, unsigned long val, enum severity strict);
+
+void bc_uncharge_locked(struct beancounter *bc,
+		int res, unsigned long val);
+void bc_uncharge(struct beancounter *bc,
+		int res, unsigned long val);
+
+struct beancounter *beancounter_findcreate(uid_t id, int mask);
+
+static inline struct beancounter *get_beancounter(struct beancounter *bc)
+{
+	atomic_inc(&bc->bc_refcount);
+	return bc;
+}
+
+void __put_beancounter(struct beancounter *bc);
+static inline void put_beancounter(struct beancounter *bc)
+{
+	__put_beancounter(bc);
+}
+
+void bc_init_early(void);
+void bc_init_late(void);
+void bc_init_proc(void);
+
+extern struct beancounter init_bc;
+extern const char *bc_rnames[];
+
+#else /* CONFIG_BEANCOUNTERS */
+
+#define beancounter_findcreate(id, f)			(NULL)
+#define get_beancounter(bc)				(NULL)
+#define put_beancounter(bc)				do { } while (0)
+#define bc_charge_locked(bc, r, v, s)			(0)
+#define bc_charge(bc, r, v)				(0)
+#define bc_uncharge_locked(bc, r, v)			do { } while (0)
+#define bc_uncharge(bc, r, v)				do { } while (0)
+#define bc_init_early()					do { } while (0)
+#define bc_init_late()					do { } while (0)
+#define bc_init_proc()					do { } while (0)
+
+#endif /* CONFIG_BEANCOUNTERS */
+#endif /* __KERNEL__ */
+
+#endif /* _LINUX_BEANCOUNTER_H */
--- ./init/main.c.ve1	2006-08-21 12:25:13.000000000 +0400
+++ ./init/main.c	2006-08-21 12:45:32.000000000 +0400
@@ -52,6 +52,8 @@
#include <linux/debug_locks.h>
#include <linux/lockdep.h>

+#include <bc/beancounter.h>
+
#include <asm/io.h>
#include <asm/bugs.h>
#include <asm/setup.h>
@@ -494,6 +496,7 @@ asmlinkage void __init start_kernel(void
	early_boot_irqs_off();
	early_init_irq_lock_class();

+	bc_init_early();
/*
 * Interrupts are still disabled. Do necessary setups, then
 * enable them
@@ -587,6 +590,7 @@ asmlinkage void __init start_kernel(void
#endif
	fork_init(num_physpages);
	proc_caches_init();
+	bc_init_late();
	buffer_init();
	unnamed_dev_init();
	key_init();
--- ./kernel/Makefile.ve1	2006-08-21 12:25:14.000000000 +0400
+++ ./kernel/Makefile	2006-08-21 12:25:27.000000000 +0400
@@ -12,6 +12,7 @@ obj-y     = sched.o fork.o exec_domain.o

obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-y += time/
+obj-y += bc/
obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o
obj-$(CONFIG_LOCKDEP) += lockdep.o
ifeq ($(CONFIG_PROC_FS),y)
--- /dev/null	2006-07-18 14:52:43.075228448 +0400
+++ ./kernel/bc/Makefile	2006-08-21 12:25:27.000000000 +0400
@@ -0,0 +1,7 @@
+#
+# Beancounters (BC)
+#
+# Copyright (C) 2006 OpenVZ. SWsoft Inc
+#
+
+obj-$(CONFIG_BEANCOUNTERS) += beancounter.o
--- /dev/null	2006-07-18 14:52:43.075228448 +0400
+++ ./kernel/bc/beancounter.c	2006-08-21 13:13:11.000000000 +0400
@@ -0,0 +1,292 @@
+/*
+ *  kernel/bc/beancounter.c
+ *
+ *  Copyright (C) 2006 OpenVZ. SWsoft Inc
+ *  Original code by (C) 1998      Alan Cox
+ *                       1998-2000 Andrey Savochkin <saw@xxxxxxxxxxxxx>
+ */
+
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#include <bc/beancounter.h>
+
+static kmem_cache_t *bc_cachep;
+static struct beancounter default_beancounter;
+
+static void init_beancounter_struct(struct beancounter *bc, uid_t id);
+
+struct beancounter init_bc;
+
+const char *bc_rnames[] = {
+};
+
+#define bc_hash_fun(x) ((((x) >> 8) ^ (x)) & (BC_HASH_SIZE - 1))
+
+struct hlist_head bc_hash[BC_HASH_SIZE];
+spinlock_t bc_hash_lock;
+
+EXPORT_SYMBOL(bc_hash);
+EXPORT_SYMBOL(bc_hash_lock);
+
+/*
+ *	Per resource beancounting. Resources are tied to their luid.
+ *	The resource structure itself is tagged both to the process and
+ *	the charging resources (a socket doesn't want to have to search for
+ *	things at irq time for example). Reference counters keep things in
+ *	hand.
+ *
+ *	The case where a user creates resource, kills all his processes and
+ *	then starts new ones is correctly handled this way. The refcounters
+ *	will mean the old entry is still around with resource tied to it.
+ */
+
+struct beancounter *beancounter_findcreate(uid_t uid, int mask)
+{
+	struct beancounter *new_bc, *bc;
+	unsigned long flags;
+	struct hlist_head *slot;
+	struct hlist_node *pos;
+
+	slot = &bc_hash[bc_hash_fun(uid)];
+	new_bc = NULL;
+
+retry:
+	spin_lock_irqsave(&bc_hash_lock, flags);
+	hlist_for_each_entry (bc, pos, slot, hash)
+		if (bc->bc_id == uid)
+			break;
+
+	if (pos != NULL) {
+		get_beancounter(bc);
+		spin_unlock_irqrestore(&bc_hash_lock, flags);
+
+		if (new_bc != NULL)
+			kmem_cache_free(bc_cachep, new_bc);
+		return bc;
+	}
+
+	if (!(mask & BC_ALLOC))
+		goto out_unlock;
+
+	if (new_bc != NULL)
+		goto out_install;
+
+	spin_unlock_irqrestore(&bc_hash_lock, flags);
+
+	new_bc = kmem_cache_alloc(bc_cachep,
+			mask & BC_ALLOC_ATOMIC ? GFP_ATOMIC : GFP_KERNEL);
+	if (new_bc == NULL)
+		goto out;
+
+	memcpy(new_bc, &default_beancounter, sizeof(*new_bc));
+	init_beancounter_struct(new_bc, uid);
+	goto retry;
+
+out_install:
+	hlist_add_head(&new_bc->hash, slot);
+out_unlock:
+	spin_unlock_irqrestore(&bc_hash_lock, flags);
+out:
+	return new_bc;
+}
+
+void bc_print_id(struct beancounter *bc, char *str, int size)
+{
+	snprintf(str, size, "%u", bc->bc_id);
+}
+
+void bc_print_resource_warning(struct beancounter *bc, int res,
+		char *str, unsigned long val, unsigned long held)
+{
+	char uid[64];
+
+	bc_print_id(bc, uid, sizeof(uid));
+	printk(KERN_WARNING "BC %s %s warning: %s "
+			"(held %lu, fails %lu, val %lu)\n",
+			uid, bc_rnames[res], str,
+			(res < BC_RESOURCES ? bc->bc_parms[res].held : held),
+			(res < BC_RESOURCES ? bc->bc_parms[res].failcnt : 0),
+			val);
+}
+
+static inline void verify_held(struct beancounter *bc)
+{
+	int i;
+
+	for (i = 0; i < BC_RESOURCES; i++)
+		if (bc->bc_parms[i].held != 0)
+			bc_print_resource_warning(bc, i,
+					"resource is held on put", 0, 0);
+}
+
+void __put_beancounter(struct beancounter *bc)
+{
+	unsigned long flags;
+
+	/* equivalent to atomic_dec_and_lock_irqsave() */
+	local_irq_save(flags);
+	if (likely(!atomic_dec_and_lock(&bc->bc_refcount, &bc_hash_lock))) {
+		local_irq_restore(flags);
+		if (unlikely(atomic_read(&bc->bc_refcount) < 0))
+			printk(KERN_ERR "BC: Bad refcount: bc=%p, "
+					"luid=%d, ref=%d\n",
+					bc, bc->bc_id,
+					atomic_read(&bc->bc_refcount));
+		return;
+	}
+
+	BUG_ON(bc == &init_bc);
+	verify_held(bc);
+	hlist_del(&bc->hash);
+	spin_unlock_irqrestore(&bc_hash_lock, flags);
+	kmem_cache_free(bc_cachep, bc);
+}
+
+EXPORT_SYMBOL(__put_beancounter);
+
+/*
+ *	Generic resource charging stuff
+ */
+
+/* called with bc->bc_lock held and interrupts disabled */
+int bc_charge_locked(struct beancounter *bc, int resource, unsigned long val,
+		enum severity strict)
+{
+	/*
+	 * bc_value <= BC_MAXVALUE, value <= BC_MAXVALUE, and only one addition
+	 * at the moment is possible so an overflow is impossible.  
+	 */
+	bc->bc_parms[resource].held += val;
+
+	switch (strict) {
+		case BC_BARRIER:
+			if (bc->bc_parms[resource].held >
+					bc->bc_parms[resource].barrier)
+				break;
+			/* fallthrough */
+		case BC_LIMIT:
+			if (bc->bc_parms[resource].held >
+					bc->bc_parms[resource].limit)
+				break;
+			/* fallthrough */
+		case BC_FORCE:
+			bc_adjust_held_minmax(bc, resource);
+			return 0;
+		default:
+			BUG();
+	}
+
+	bc->bc_parms[resource].failcnt++;
+	bc->bc_parms[resource].held -= val;
+	return -ENOMEM;
+}
+EXPORT_SYMBOL(bc_charge_locked);
+
+int bc_charge(struct beancounter *bc, int resource, unsigned long val,
+		enum severity strict)
+{
+	int retval;
+	unsigned long flags;
+
+	BUG_ON(val > BC_MAXVALUE);
+
+	spin_lock_irqsave(&bc->bc_lock, flags);
+	retval = bc_charge_locked(bc, resource, val, strict);
+	spin_unlock_irqrestore(&bc->bc_lock, flags);
+	return retval;
+}
+EXPORT_SYMBOL(bc_charge);
+
+/* called with bc->bc_lock held and interrupts disabled */
+void bc_uncharge_locked(struct beancounter *bc, int resource, unsigned long val)
+{
+	if (unlikely(bc->bc_parms[resource].held < val)) {
+		bc_print_resource_warning(bc, resource,
+				"uncharging too much", val, 0);
+		val = bc->bc_parms[resource].held;
+	}
+
+	bc->bc_parms[resource].held -= val;
+	bc_adjust_held_minmax(bc, resource);
+}
+EXPORT_SYMBOL(bc_uncharge_locked);
+
+void bc_uncharge(struct beancounter *bc, int resource, unsigned long val)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&bc->bc_lock, flags);
+	bc_uncharge_locked(bc, resource, val);
+	spin_unlock_irqrestore(&bc->bc_lock, flags);
+}
+EXPORT_SYMBOL(bc_uncharge);
+
+/*
+ *	Initialization
+ *
+ *	struct beancounter contains
+ *	 - limits and other configuration settings
+ *	 - structural fields: lists, spinlocks and so on.
+ *
+ *	Before these parts are initialized, the structure should be memset
+ *	to 0 or copied from a known clean structure.  That takes care of a lot
+ *	of fields not initialized explicitly.
+ */
+
+static void init_beancounter_struct(struct beancounter *bc, uid_t id)
+{
+	atomic_set(&bc->bc_refcount, 1);
+	spin_lock_init(&bc->bc_lock);
+	bc->bc_id = id;
+}
+
+static void init_beancounter_nolimits(struct beancounter *bc)
+{
+	int k;
+
+	for (k = 0; k < BC_RESOURCES; k++) {
+		bc->bc_parms[k].limit = BC_MAXVALUE;
+		bc->bc_parms[k].barrier = BC_MAXVALUE;
+	}
+}
+
+static void init_beancounter_syslimits(struct beancounter *bc)
+{
+	int k;
+
+	for (k = 0; k < BC_RESOURCES; k++)
+		bc->bc_parms[k].barrier = bc->bc_parms[k].limit;
+}
+
+void __init bc_init_early(void)
+{
+	struct beancounter *bc;
+	struct hlist_head *slot;
+
+	bc = &init_bc;
+
+	memset(bc, 0, sizeof(*bc));
+	init_beancounter_nolimits(bc);
+	init_beancounter_struct(bc, 0);
+
+	spin_lock_init(&bc_hash_lock);
+	slot = &bc_hash[bc_hash_fun(bc->bc_id)];
+	hlist_add_head(&bc->hash, slot);
+}
+
+void __init bc_init_late(void)
+{
+	struct beancounter *bc;
+
+	bc_cachep = kmem_cache_create("beancounters",
+			sizeof(struct beancounter),
+			0, SLAB_HWCACHE_ALIGN, NULL, NULL);
+	if (bc_cachep == NULL)
+		panic("Can't create bc caches\n");
+
+	bc = &default_beancounter;
+	memset(bc, 0, sizeof(default_beancounter));
+	init_beancounter_syslimits(bc);
+	init_beancounter_struct(bc, 0);
+}
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