Commit 5b1efc02 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
Browse files

kernel: res_counter: remove the unused API



All memory accounting and limiting has been switched over to the
lockless page counters.  Bye, res_counter!

[akpm@linux-foundation.org: update Documentation/cgroups/memory.txt]
[mhocko@suse.cz: ditch the last remainings of res_counter]
Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarVladimir Davydov <vdavydov@parallels.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 71f87bee
......@@ -116,16 +116,16 @@ The memory controller is the first controller developed.
2.1. Design
The core of the design is a counter called the res_counter. The res_counter
tracks the current memory usage and limit of the group of processes associated
with the controller. Each cgroup has a memory controller specific data
structure (mem_cgroup) associated with it.
The core of the design is a counter called the page_counter. The
page_counter tracks the current memory usage and limit of the group of
processes associated with the controller. Each cgroup has a memory controller
specific data structure (mem_cgroup) associated with it.
2.2. Accounting
+--------------------+
| mem_cgroup |
| (res_counter) |
| mem_cgroup |
| (page_counter) |
+--------------------+
/ ^ \
/ | \
......@@ -352,9 +352,8 @@ set:
0. Configuration
a. Enable CONFIG_CGROUPS
b. Enable CONFIG_RESOURCE_COUNTERS
c. Enable CONFIG_MEMCG
d. Enable CONFIG_MEMCG_SWAP (to use swap extension)
b. Enable CONFIG_MEMCG
c. Enable CONFIG_MEMCG_SWAP (to use swap extension)
d. Enable CONFIG_MEMCG_KMEM (to use kmem extension)
1. Prepare the cgroups (see cgroups.txt, Why are cgroups needed?)
......
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 :)
#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@openvz.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
......@@ -972,12 +972,6 @@ 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
......
......@@ -57,7 +57,6 @@ obj-$(CONFIG_UTS_NS) += utsname.o
obj-$(CONFIG_USER_NS) += user_namespace.o
obj-$(CONFIG_PID_NS) += pid_namespace.o
obj-$(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
......
/*
* resource cgroups
*
* Copyright 2007 OpenVZ SWsoft Inc
*
* Author: Pavel Emelianov <xemul@openvz.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;