Date:	Tue, 7 Oct 2014 17:26:32 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	linux-mm@...ck.org, Vladimir Davydov <vdavydov@...allels.com>,
	Greg Thelen <gthelen@...gle.com>, Dave Hansen <dave@...1.net>,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 3/3] kernel: res_counter: remove the unused API

On Wed 24-09-14 11:43:10, Johannes Weiner wrote:
> All memory accounting and limiting has been switched over to the
> lockless page counters.  Bye, res_counter!
> 

More than happily
Acked-by: Michal Hocko <mhocko@...e.cz>

> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> ---
>  Documentation/cgroups/resource_counter.txt | 197 -------------------------
>  include/linux/res_counter.h                | 223 -----------------------------
>  init/Kconfig                               |   6 -
>  kernel/Makefile                            |   1 -
>  kernel/res_counter.c                       | 211 ---------------------------
>  5 files changed, 638 deletions(-)
>  delete mode 100644 Documentation/cgroups/resource_counter.txt
>  delete mode 100644 include/linux/res_counter.h
>  delete mode 100644 kernel/res_counter.c
> 
> diff --git a/Documentation/cgroups/resource_counter.txt b/Documentation/cgroups/resource_counter.txt
> deleted file mode 100644
> index 762ca54eb929..000000000000
> --- a/Documentation/cgroups/resource_counter.txt
> +++ /dev/null
> @@ -1,197 +0,0 @@
> -
> -		The Resource Counter
> -
> -The resource counter, declared at include/linux/res_counter.h,
> -is supposed to facilitate the resource management by controllers
> -by providing common stuff for accounting.
> -
> -This "stuff" includes the res_counter structure and routines
> -to work with it.
> -
> -
> -
> -1. Crucial parts of the res_counter structure
> -
> - a. unsigned long long usage
> -
> - 	The usage value shows the amount of a resource that is consumed
> -	by a group at a given time. The units of measurement should be
> -	determined by the controller that uses this counter. E.g. it can
> -	be bytes, items or any other unit the controller operates on.
> -
> - b. unsigned long long max_usage
> -
> - 	The maximal value of the usage over time.
> -
> - 	This value is useful when gathering statistical information about
> -	the particular group, as it shows the actual resource requirements
> -	for a particular group, not just some usage snapshot.
> -
> - c. unsigned long long limit
> -
> - 	The maximal allowed amount of resource to consume by the group. In
> -	case the group requests for more resources, so that the usage value
> -	would exceed the limit, the resource allocation is rejected (see
> -	the next section).
> -
> - d. unsigned long long failcnt
> -
> - 	The failcnt stands for "failures counter". This is the number of
> -	resource allocation attempts that failed.
> -
> - c. spinlock_t lock
> -
> - 	Protects changes of the above values.
> -
> -
> -
> -2. Basic accounting routines
> -
> - a. void res_counter_init(struct res_counter *rc,
> -				struct res_counter *rc_parent)
> -
> - 	Initializes the resource counter. As usual, should be the first
> -	routine called for a new counter.
> -
> -	The struct res_counter *parent can be used to define a hierarchical
> -	child -> parent relationship directly in the res_counter structure,
> -	NULL can be used to define no relationship.
> -
> - c. int res_counter_charge(struct res_counter *rc, unsigned long val,
> -				struct res_counter **limit_fail_at)
> -
> -	When a resource is about to be allocated it has to be accounted
> -	with the appropriate resource counter (controller should determine
> -	which one to use on its own). This operation is called "charging".
> -
> -	This is not very important which operation - resource allocation
> -	or charging - is performed first, but
> -	  * if the allocation is performed first, this may create a
> -	    temporary resource over-usage by the time resource counter is
> -	    charged;
> -	  * if the charging is performed first, then it should be uncharged
> -	    on error path (if the one is called).
> -
> -	If the charging fails and a hierarchical dependency exists, the
> -	limit_fail_at parameter is set to the particular res_counter element
> -	where the charging failed.
> -
> - d. u64 res_counter_uncharge(struct res_counter *rc, unsigned long val)
> -
> -	When a resource is released (freed) it should be de-accounted
> -	from the resource counter it was accounted to.  This is called
> -	"uncharging". The return value of this function indicate the amount
> -	of charges still present in the counter.
> -
> -	The _locked routines imply that the res_counter->lock is taken.
> -
> - e. u64 res_counter_uncharge_until
> -		(struct res_counter *rc, struct res_counter *top,
> -		 unsigned long val)
> -
> -	Almost same as res_counter_uncharge() but propagation of uncharge
> -	stops when rc == top. This is useful when kill a res_counter in
> -	child cgroup.
> -
> - 2.1 Other accounting routines
> -
> -    There are more routines that may help you with common needs, like
> -    checking whether the limit is reached or resetting the max_usage
> -    value. They are all declared in include/linux/res_counter.h.
> -
> -
> -
> -3. Analyzing the resource counter registrations
> -
> - a. If the failcnt value constantly grows, this means that the counter's
> -    limit is too tight. Either the group is misbehaving and consumes too
> -    many resources, or the configuration is not suitable for the group
> -    and the limit should be increased.
> -
> - b. The max_usage value can be used to quickly tune the group. One may
> -    set the limits to maximal values and either load the container with
> -    a common pattern or leave one for a while. After this the max_usage
> -    value shows the amount of memory the container would require during
> -    its common activity.
> -
> -    Setting the limit a bit above this value gives a pretty good
> -    configuration that works in most of the cases.
> -
> - c. If the max_usage is much less than the limit, but the failcnt value
> -    is growing, then the group tries to allocate a big chunk of resource
> -    at once.
> -
> - d. If the max_usage is much less than the limit, but the failcnt value
> -    is 0, then this group is given too high limit, that it does not
> -    require. It is better to lower the limit a bit leaving more resource
> -    for other groups.
> -
> -
> -
> -4. Communication with the control groups subsystem (cgroups)
> -
> -All the resource controllers that are using cgroups and resource counters
> -should provide files (in the cgroup filesystem) to work with the resource
> -counter fields. They are recommended to adhere to the following rules:
> -
> - a. File names
> -
> - 	Field name	File name
> -	---------------------------------------------------
> -	usage		usage_in_<unit_of_measurement>
> -	max_usage	max_usage_in_<unit_of_measurement>
> -	limit		limit_in_<unit_of_measurement>
> -	failcnt		failcnt
> -	lock		no file :)
> -
> - b. Reading from file should show the corresponding field value in the
> -    appropriate format.
> -
> - c. Writing to file
> -
> - 	Field		Expected behavior
> -	----------------------------------
> -	usage		prohibited
> -	max_usage	reset to usage
> -	limit		set the limit
> -	failcnt		reset to zero
> -
> -
> -
> -5. Usage example
> -
> - a. Declare a task group (take a look at cgroups subsystem for this) and
> -    fold a res_counter into it
> -
> -	struct my_group {
> -		struct res_counter res;
> -
> -		<other fields>
> -	}
> -
> - b. Put hooks in resource allocation/release paths
> -
> - 	int alloc_something(...)
> -	{
> -		if (res_counter_charge(res_counter_ptr, amount) < 0)
> -			return -ENOMEM;
> -
> -		<allocate the resource and return to the caller>
> -	}
> -
> -	void release_something(...)
> -	{
> -		res_counter_uncharge(res_counter_ptr, amount);
> -
> -		<release the resource>
> -	}
> -
> -    In order to keep the usage value self-consistent, both the
> -    "res_counter_ptr" and the "amount" in release_something() should be
> -    the same as they were in the alloc_something() when the releasing
> -    resource was allocated.
> -
> - c. Provide the way to read res_counter values and set them (the cgroups
> -    still can help with it).
> -
> - c. Compile and run :)
> diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
> deleted file mode 100644
> index 56b7bc32db4f..000000000000
> --- a/include/linux/res_counter.h
> +++ /dev/null
> @@ -1,223 +0,0 @@
> -#ifndef __RES_COUNTER_H__
> -#define __RES_COUNTER_H__
> -
> -/*
> - * Resource Counters
> - * Contain common data types and routines for resource accounting
> - *
> - * Copyright 2007 OpenVZ SWsoft Inc
> - *
> - * Author: Pavel Emelianov <xemul@...nvz.org>
> - *
> - * See Documentation/cgroups/resource_counter.txt for more
> - * info about what this counter is.
> - */
> -
> -#include <linux/spinlock.h>
> -#include <linux/errno.h>
> -
> -/*
> - * The core object. the cgroup that wishes to account for some
> - * resource may include this counter into its structures and use
> - * the helpers described beyond
> - */
> -
> -struct res_counter {
> -	/*
> -	 * the current resource consumption level
> -	 */
> -	unsigned long long usage;
> -	/*
> -	 * the maximal value of the usage from the counter creation
> -	 */
> -	unsigned long long max_usage;
> -	/*
> -	 * the limit that usage cannot exceed
> -	 */
> -	unsigned long long limit;
> -	/*
> -	 * the limit that usage can be exceed
> -	 */
> -	unsigned long long soft_limit;
> -	/*
> -	 * the number of unsuccessful attempts to consume the resource
> -	 */
> -	unsigned long long failcnt;
> -	/*
> -	 * the lock to protect all of the above.
> -	 * the routines below consider this to be IRQ-safe
> -	 */
> -	spinlock_t lock;
> -	/*
> -	 * Parent counter, used for hierarchial resource accounting
> -	 */
> -	struct res_counter *parent;
> -};
> -
> -#define RES_COUNTER_MAX ULLONG_MAX
> -
> -/**
> - * Helpers to interact with userspace
> - * res_counter_read_u64() - returns the value of the specified member.
> - * res_counter_read/_write - put/get the specified fields from the
> - * res_counter struct to/from the user
> - *
> - * @counter:     the counter in question
> - * @member:  the field to work with (see RES_xxx below)
> - * @buf:     the buffer to opeate on,...
> - * @nbytes:  its size...
> - * @pos:     and the offset.
> - */
> -
> -u64 res_counter_read_u64(struct res_counter *counter, int member);
> -
> -ssize_t res_counter_read(struct res_counter *counter, int member,
> -		const char __user *buf, size_t nbytes, loff_t *pos,
> -		int (*read_strategy)(unsigned long long val, char *s));
> -
> -int res_counter_memparse_write_strategy(const char *buf,
> -					unsigned long long *res);
> -
> -/*
> - * the field descriptors. one for each member of res_counter
> - */
> -
> -enum {
> -	RES_USAGE,
> -	RES_MAX_USAGE,
> -	RES_LIMIT,
> -	RES_FAILCNT,
> -	RES_SOFT_LIMIT,
> -};
> -
> -/*
> - * helpers for accounting
> - */
> -
> -void res_counter_init(struct res_counter *counter, struct res_counter *parent);
> -
> -/*
> - * charge - try to consume more resource.
> - *
> - * @counter: the counter
> - * @val: the amount of the resource. each controller defines its own
> - *       units, e.g. numbers, bytes, Kbytes, etc
> - *
> - * returns 0 on success and <0 if the counter->usage will exceed the
> - * counter->limit
> - *
> - * charge_nofail works the same, except that it charges the resource
> - * counter unconditionally, and returns < 0 if the after the current
> - * charge we are over limit.
> - */
> -
> -int __must_check res_counter_charge(struct res_counter *counter,
> -		unsigned long val, struct res_counter **limit_fail_at);
> -int res_counter_charge_nofail(struct res_counter *counter,
> -		unsigned long val, struct res_counter **limit_fail_at);
> -
> -/*
> - * uncharge - tell that some portion of the resource is released
> - *
> - * @counter: the counter
> - * @val: the amount of the resource
> - *
> - * these calls check for usage underflow and show a warning on the console
> - *
> - * returns the total charges still present in @counter.
> - */
> -
> -u64 res_counter_uncharge(struct res_counter *counter, unsigned long val);
> -
> -u64 res_counter_uncharge_until(struct res_counter *counter,
> -			       struct res_counter *top,
> -			       unsigned long val);
> -/**
> - * res_counter_margin - calculate chargeable space of a counter
> - * @cnt: the counter
> - *
> - * Returns the difference between the hard limit and the current usage
> - * of resource counter @cnt.
> - */
> -static inline unsigned long long res_counter_margin(struct res_counter *cnt)
> -{
> -	unsigned long long margin;
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&cnt->lock, flags);
> -	if (cnt->limit > cnt->usage)
> -		margin = cnt->limit - cnt->usage;
> -	else
> -		margin = 0;
> -	spin_unlock_irqrestore(&cnt->lock, flags);
> -	return margin;
> -}
> -
> -/**
> - * Get the difference between the usage and the soft limit
> - * @cnt: The counter
> - *
> - * Returns 0 if usage is less than or equal to soft limit
> - * The difference between usage and soft limit, otherwise.
> - */
> -static inline unsigned long long
> -res_counter_soft_limit_excess(struct res_counter *cnt)
> -{
> -	unsigned long long excess;
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&cnt->lock, flags);
> -	if (cnt->usage <= cnt->soft_limit)
> -		excess = 0;
> -	else
> -		excess = cnt->usage - cnt->soft_limit;
> -	spin_unlock_irqrestore(&cnt->lock, flags);
> -	return excess;
> -}
> -
> -static inline void res_counter_reset_max(struct res_counter *cnt)
> -{
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&cnt->lock, flags);
> -	cnt->max_usage = cnt->usage;
> -	spin_unlock_irqrestore(&cnt->lock, flags);
> -}
> -
> -static inline void res_counter_reset_failcnt(struct res_counter *cnt)
> -{
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&cnt->lock, flags);
> -	cnt->failcnt = 0;
> -	spin_unlock_irqrestore(&cnt->lock, flags);
> -}
> -
> -static inline int res_counter_set_limit(struct res_counter *cnt,
> -		unsigned long long limit)
> -{
> -	unsigned long flags;
> -	int ret = -EBUSY;
> -
> -	spin_lock_irqsave(&cnt->lock, flags);
> -	if (cnt->usage <= limit) {
> -		cnt->limit = limit;
> -		ret = 0;
> -	}
> -	spin_unlock_irqrestore(&cnt->lock, flags);
> -	return ret;
> -}
> -
> -static inline int
> -res_counter_set_soft_limit(struct res_counter *cnt,
> -				unsigned long long soft_limit)
> -{
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&cnt->lock, flags);
> -	cnt->soft_limit = soft_limit;
> -	spin_unlock_irqrestore(&cnt->lock, flags);
> -	return 0;
> -}
> -
> -#endif
> diff --git a/init/Kconfig b/init/Kconfig
> index eddec767b7ee..e503efe34bc0 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -977,12 +977,6 @@ config CGROUP_CPUACCT
>  	  Provides a simple Resource Controller for monitoring the
>  	  total CPU consumed by the tasks in a cgroup.
>  
> -config RESOURCE_COUNTERS
> -	bool "Resource counters"
> -	help
> -	  This option enables controller independent resource accounting
> -	  infrastructure that works with cgroups.
> -
>  config PAGE_COUNTER
>         bool
>  
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 726e18443da0..245953354974 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -58,7 +58,6 @@ obj-$(CONFIG_USER_NS) += user_namespace.o
>  obj-$(CONFIG_PID_NS) += pid_namespace.o
>  obj-$(CONFIG_DEBUG_SYNCHRO_TEST) += synchro-test.o
>  obj-$(CONFIG_IKCONFIG) += configs.o
> -obj-$(CONFIG_RESOURCE_COUNTERS) += res_counter.o
>  obj-$(CONFIG_SMP) += stop_machine.o
>  obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
>  obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
> diff --git a/kernel/res_counter.c b/kernel/res_counter.c
> deleted file mode 100644
> index e791130f85a7..000000000000
> --- a/kernel/res_counter.c
> +++ /dev/null
> @@ -1,211 +0,0 @@
> -/*
> - * resource cgroups
> - *
> - * Copyright 2007 OpenVZ SWsoft Inc
> - *
> - * Author: Pavel Emelianov <xemul@...nvz.org>
> - *
> - */
> -
> -#include <linux/types.h>
> -#include <linux/parser.h>
> -#include <linux/fs.h>
> -#include <linux/res_counter.h>
> -#include <linux/uaccess.h>
> -#include <linux/mm.h>
> -
> -void res_counter_init(struct res_counter *counter, struct res_counter *parent)
> -{
> -	spin_lock_init(&counter->lock);
> -	counter->limit = RES_COUNTER_MAX;
> -	counter->soft_limit = RES_COUNTER_MAX;
> -	counter->parent = parent;
> -}
> -
> -static u64 res_counter_uncharge_locked(struct res_counter *counter,
> -				       unsigned long val)
> -{
> -	if (WARN_ON(counter->usage < val))
> -		val = counter->usage;
> -
> -	counter->usage -= val;
> -	return counter->usage;
> -}
> -
> -static int res_counter_charge_locked(struct res_counter *counter,
> -				     unsigned long val, bool force)
> -{
> -	int ret = 0;
> -
> -	if (counter->usage + val > counter->limit) {
> -		counter->failcnt++;
> -		ret = -ENOMEM;
> -		if (!force)
> -			return ret;
> -	}
> -
> -	counter->usage += val;
> -	if (counter->usage > counter->max_usage)
> -		counter->max_usage = counter->usage;
> -	return ret;
> -}
> -
> -static int __res_counter_charge(struct res_counter *counter, unsigned long val,
> -				struct res_counter **limit_fail_at, bool force)
> -{
> -	int ret, r;
> -	unsigned long flags;
> -	struct res_counter *c, *u;
> -
> -	r = ret = 0;
> -	*limit_fail_at = NULL;
> -	local_irq_save(flags);
> -	for (c = counter; c != NULL; c = c->parent) {
> -		spin_lock(&c->lock);
> -		r = res_counter_charge_locked(c, val, force);
> -		spin_unlock(&c->lock);
> -		if (r < 0 && !ret) {
> -			ret = r;
> -			*limit_fail_at = c;
> -			if (!force)
> -				break;
> -		}
> -	}
> -
> -	if (ret < 0 && !force) {
> -		for (u = counter; u != c; u = u->parent) {
> -			spin_lock(&u->lock);
> -			res_counter_uncharge_locked(u, val);
> -			spin_unlock(&u->lock);
> -		}
> -	}
> -	local_irq_restore(flags);
> -
> -	return ret;
> -}
> -
> -int res_counter_charge(struct res_counter *counter, unsigned long val,
> -			struct res_counter **limit_fail_at)
> -{
> -	return __res_counter_charge(counter, val, limit_fail_at, false);
> -}
> -
> -int res_counter_charge_nofail(struct res_counter *counter, unsigned long val,
> -			      struct res_counter **limit_fail_at)
> -{
> -	return __res_counter_charge(counter, val, limit_fail_at, true);
> -}
> -
> -u64 res_counter_uncharge_until(struct res_counter *counter,
> -			       struct res_counter *top,
> -			       unsigned long val)
> -{
> -	unsigned long flags;
> -	struct res_counter *c;
> -	u64 ret = 0;
> -
> -	local_irq_save(flags);
> -	for (c = counter; c != top; c = c->parent) {
> -		u64 r;
> -		spin_lock(&c->lock);
> -		r = res_counter_uncharge_locked(c, val);
> -		if (c == counter)
> -			ret = r;
> -		spin_unlock(&c->lock);
> -	}
> -	local_irq_restore(flags);
> -	return ret;
> -}
> -
> -u64 res_counter_uncharge(struct res_counter *counter, unsigned long val)
> -{
> -	return res_counter_uncharge_until(counter, NULL, val);
> -}
> -
> -static inline unsigned long long *
> -res_counter_member(struct res_counter *counter, int member)
> -{
> -	switch (member) {
> -	case RES_USAGE:
> -		return &counter->usage;
> -	case RES_MAX_USAGE:
> -		return &counter->max_usage;
> -	case RES_LIMIT:
> -		return &counter->limit;
> -	case RES_FAILCNT:
> -		return &counter->failcnt;
> -	case RES_SOFT_LIMIT:
> -		return &counter->soft_limit;
> -	};
> -
> -	BUG();
> -	return NULL;
> -}
> -
> -ssize_t res_counter_read(struct res_counter *counter, int member,
> -		const char __user *userbuf, size_t nbytes, loff_t *pos,
> -		int (*read_strategy)(unsigned long long val, char *st_buf))
> -{
> -	unsigned long long *val;
> -	char buf[64], *s;
> -
> -	s = buf;
> -	val = res_counter_member(counter, member);
> -	if (read_strategy)
> -		s += read_strategy(*val, s);
> -	else
> -		s += sprintf(s, "%llu\n", *val);
> -	return simple_read_from_buffer((void __user *)userbuf, nbytes,
> -			pos, buf, s - buf);
> -}
> -
> -#if BITS_PER_LONG == 32
> -u64 res_counter_read_u64(struct res_counter *counter, int member)
> -{
> -	unsigned long flags;
> -	u64 ret;
> -
> -	spin_lock_irqsave(&counter->lock, flags);
> -	ret = *res_counter_member(counter, member);
> -	spin_unlock_irqrestore(&counter->lock, flags);
> -
> -	return ret;
> -}
> -#else
> -u64 res_counter_read_u64(struct res_counter *counter, int member)
> -{
> -	return *res_counter_member(counter, member);
> -}
> -#endif
> -
> -int res_counter_memparse_write_strategy(const char *buf,
> -					unsigned long long *resp)
> -{
> -	char *end;
> -	unsigned long long res;
> -
> -	/* return RES_COUNTER_MAX(unlimited) if "-1" is specified */
> -	if (*buf == '-') {
> -		int rc = kstrtoull(buf + 1, 10, &res);
> -
> -		if (rc)
> -			return rc;
> -		if (res != 1)
> -			return -EINVAL;
> -		*resp = RES_COUNTER_MAX;
> -		return 0;
> -	}
> -
> -	res = memparse(buf, &end);
> -	if (*end != '\0')
> -		return -EINVAL;
> -
> -	if (PAGE_ALIGN(res) >= res)
> -		res = PAGE_ALIGN(res);
> -	else
> -		res = RES_COUNTER_MAX;
> -
> -	*resp = res;
> -
> -	return 0;
> -}
> -- 
> 2.1.0
> 

-- 
Michal Hocko
SUSE Labs
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