diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/cgroups/memory.txt | 17 | ||||
| -rw-r--r-- | Documentation/cgroups/resource_counter.txt | 197 |
2 files changed, 8 insertions, 206 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index f624727ab404..67613ff0270c 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -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?) 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 :) |