Re: [PATCH] Memory controller Add Documentation
On Wed, 22 Aug 2007 18:36:12 +0530 Balbir Singh wrote: > Documentation/memcontrol.txt | 193 +++++++++++++++++++++++++++++++++++++++++++ Is there some sub-dir that is appropriate for this, such as vm/ or accounting/ or containers/ (new) ? > 1 file changed, 193 insertions(+) > > diff -puN /dev/null Documentation/memcontrol.txt > --- /dev/null 2007-06-01 20:42:04.000000000 +0530 > +++ linux-2.6.23-rc2-mm2-balbir/Documentation/memcontrol.txt 2007-08-22 18:29:29.000000000 +0530 > @@ -0,0 +1,193 @@ > +Memory Controller > + > +0. Salient features > + > +a. Enable control of both RSS and Page Cache pages > +b. The infrastructures allows easy addition of other types of memory to control infrastructure > +c. Provides *zero overhead* for non memory controller users > +d. Provides a double LRU, global memory pressure causes reclaim from the > + global LRU, a container on hitting a limit, reclaims from the per > + container LRU Punctuation: Provides a double LRU: global memory pressure causes reclaim from the global LRU; a container, on hitting a limit, reclaims from the per- container LRU > + > +1. History > + > +The memory controller has a long history. A request for comments for the memory > +controller was posted by Balbir Singh [1]. At the time the RFC was posted > +there were several implementations for memory control, the goal of the s/, the/. The/ > +RFC was to build consensus and agreement for the minimal features required > +for memory control. The first RSS controller was posted by Balbir Singh[2] > +in Feb 2007. Pavel Emelianov [3][4][5] has since posted three versions of the > +RSS controller. At OLS, at the resource management BoF, everyone suggested > +that we handle both page cache and RSS together. Another request was raised > +to allow user space handling of OOM. The current memory controller is > +at version 6, it combines both RSS and Page Cache Control [11]. s/,/;/ > + > +2. Memory Control > + > +Memory is a unique resource in the sense that it is present in a limited > +amount. If a task requires a lot of CPU processing, the task can spread > +its processing over a period of hours, days, months or years, but with > +memory, the same physical memory needs to be reused to accomplish the task. > + > +The memory controller implementation has been divided into phases, these > +are Punctuation: The memory controller implementation has been divided into phases. These are: > + > +1. Memory controller > +2. mlock(2) controller > +3. Kernel user memory accounting and slab control > +4. user mappings length controller > + > +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 container has a memory controller specific data > +structure (mem_container) associated with it. > + > +2.2. Accounting > + > + +--------------------+ > + | mem_container | > + | (res_counter) | > + +--------------------+ > + / ^ \ > + / | \ > + +---------------+ | +---------------+ > + | mm_struct | |.... | mm_struct | > + | | | | | > + +---------------+ | +---------------+ > + | > + + --------------+ > + | > + +---------------+ +------+--------+ > + | page +----------> page_container| > + | | | | > + +---------------+ +---------------+ > + > + (Figure 1: Hierarchy of Accounting) > + > + > +Figure 1 shows the important aspects of the controller > + > +1. Accounting happens per container > +2. Each mm_struct knows about which container they belong to it belongs to > +3. Each page has a pointer to the page_container, which in turn knows the > + container it belongs to > + > +The accounting is done as follows, mem_container_charge() is invoked to setup as follows: > +the necessary data structures and check if the container that is being charged > +is over its limit. If it is then reclaim is invoked on the container. > +More details can be found in the reclaim section of this document. > +If everything goes well, a page meta-data-structure called page_container is > +allocated and associated with the page. This routine also adds the page to > +the per container LRU. > + > +2.3 Shared Page Accounting > + > +Shared pages are accounted on the basis of the first touch approach. The > +container that first touches a page is accounted for the page. The principle > +behind this approach is that a container that aggressively uses a shared > +page, will eventually get charged for it (once it is uncharged from drop comma > +the container that brought it in -- this will happen on memory pressure). > + > +2.4 Reclaim > + > +Each container maintains a per container LRU that consists of an active > +and inactive list. When a container goes over its limit, we first try > +and reclaim memory from the container so as to make space for the new to reclaim memory > +pages that the container has touched. If the reclaim is unsuccessful, > +an OOM routine is invoked to select and kill the bulkiest task in the > +container. > + > +The reclaim algorithm has not been modified for containers, except that > +pages that are selected for reclaiming come from the per container LRU > +list. > + > +2.5 > + > +3. User Interface > + > +0. Configuration > + > +a. Enable CONFIG_CONTAINERS > +b. Enable CONFIG_RESOURCE_COUNTERS > +c. Enable CONFIG_CONTAINER_MEM_CONT > + > +1. Prepare the containers > +# mkdir -p /containers > +# mount -t container none /containers -o memory > + > +2. Make the new group and move bash into it > +# mkdir /containers/0 > +# echo $$ > /containers/0/tasks > + > +Since now we're in the 0 container. s/./,/ > +We can alter the memory limit we can alter the memory limit: > +# echo -n 6000 > /containers/0/memory.limit > + > +We can check the usage : > +# cat /containers/0/memory.usage > +25 > + > +The memory.failcnt gives the number of times that the container limit was memory.failcnt field (?) > +exceeded. > + > +4. Testing > + > +Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11]. > +Apart from that v6 has been tested with several applications and regular > +daily use. The controller has also been tested on the PPC64, x86_64 and > +UML platforms. > + > +4.1 Troubleshooting > + > +Sometimes a user might find that the application under a container is > +terminated, there are several causes for this Punctuation + wording: Sometimes a user might find that the application under a container is terminated. There are several possible causes of this: > + > +1. The container limit is too low (just too low to do anything useful) > +2. The user is using anonymous memory and swap is turned off or too low > + > +echo 1 > /proc/sys/vm/drop_pages will help get rid of some of the pages > +cached in the container (page cache pages). > + > +5. TODO > + > +1. Add support for accounting huge pages (as a separate controller) > +2. Improve the user interface to accept/display memory limits in KB or MB > + rather than pages (since page sizes can differ across platforms/machines). > +3. Make container lists per-zone > +4. Make per-container scanner reclaim not-shared pages first > +5. Teach controller to account for shared-pages > +6. Start reclamation when the limit is lowered > +7. Start reclamation in the background when the limit is > + not yet hit but the usage is getting closer > +8. Create per zone LRU lists per container > + > +Summary > + > +Overall, the memory controller has been a stable controller and has been > +commented and discussed on quite extensively in the community. drop "on" > + > +References > + > +1. Singh, Balbir. RFC: Memory Controller, http://lwn.net/Articles/206697/ > +2. Singh, Balbir. Memory Controller (RSS Control), > + http://lwn.net/Articles/222762/ > +3. Emelianov, Pavel. Resource controllers based on process containers > + http://lkml.org/lkml/2007/3/6/198 > +4. Emelianov, Pavel. RSS controller based on process containers (v2) > + http://lkml.org/lkml/2007/4/9/74 > +5. Emelianov, Pavel. RSS controller based on process containers (v3) > + http://lkml.org/lkml/2007/5/30/244 > +6. Menage, Paul. Containers v10, http://lwn.net/Articles/236032/ > +7. Vaidyanathan, Srinivasan, Containers: Pagecache accounting and control > + subsystem (v3), http://lwn.net/Articles/235534/ > +8. Singh, Balbir. RSS controller V2 test results (lmbench), > + http://lkml.org/lkml/2007/5/17/232 > +9. Singh, Balbir. RSS controller V2 AIM9 results > + http://lkml.org/lkml/2007/5/18/1 > +10. Singh, Balbir. Memory controller v6 results, > + http://lkml.org/lkml/2007/8/19/36 > +11. Singh, Balbir. Memory controller v6, http://lkml.org/lkml/2007/8/17/69 --- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code *** _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/containers
Randy Dunlap wrote: > On Wed, 22 Aug 2007 18:36:12 +0530 Balbir Singh wrote: > >> Documentation/memcontrol.txt | 193 +++++++++++++++++++++++++++++++++++++++++++ > > Is there some sub-dir that is appropriate for this, such as > vm/ or accounting/ or containers/ (new) ? > > <snip> Hi, Randy, Thanks for the detailed review. Most of the comments seem valid, I will fix them in the next release. -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL _______________________________________________ Containers mailing list Containers@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/containers