Messages in this thread | | | Date | Tue, 18 Sep 2007 09:53:13 -0700 | From | Randy Dunlap <> | Subject | Re: [PATCH 20/33] memory controller add documentation |
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On Mon, 17 Sep 2007 14:03:27 -0700 Paul Menage wrote:
> From: Balbir Singh <balbir@linux.vnet.ibm.com> > (container->cgroup renaming by Paul Menage <menage@google.com>) > > Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> > Signed-off-by: Paul Menage <menage@google.com> > > --- > > Documentation/controllers/memory.txt | 259 +++++++++++++++++++++++++ > 1 files changed, 259 insertions(+) > > diff -puN /dev/null Documentation/controllers/memory.txt > --- /dev/null > +++ a/Documentation/controllers/memory.txt > @@ -0,0 +1,259 @@
> +Benefits and Purpose of the memory controller > + > +The memory controller isolates the memory behaviour of a group of tasks > +from the rest of the system. The article on LWN [12] mentions some probable > +uses of the memory controller. The memory controller can be used to > + > +a. Isolate an application or a group of applications > + Memory hungry applications can be isolated and limited to a smaller > + amount of memory. > +b. Create a cgroup with limited amount of memory, this can be used
"," makes run-on sentence. Please use ";" or 2 sentences.
> + as a good alternative to booting with mem=XXXX. > +c. Virtualization solutions can control the amount of memory they want > + to assign to a virtual machine instance. > +d. A CD/DVD burner could control the amount of memory used by the > + rest of the system to ensure that burning does not fail due to lack > + of available memory. > +e. There are several other use cases, find one or use the controller just
Ditto.
> + for fun (to learn and hack on the VM subsystem).
[snip]
> + > +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. > + > +2.2. Accounting > + [snip] > + > +The accounting is done as follows: mem_cgroup_charge() is invoked to setup > +the necessary data structures and check if the cgroup that is being charged > +is over its limit. If it is then reclaim is invoked on the cgroup. > +More details can be found in the reclaim section of this document. > +If everything goes well, a page meta-data-structure called page_cgroup is
^drop second hyphen (use space)
> +allocated and associated with the page. This routine also adds the page to > +the per cgroup LRU. > + > +2.2.1 Accounting details > + > +All mapped pages (RSS) and unmapped user pages (Page Cache) are accounted. > +RSS pages are accounted at the time of page_add_*_rmap() unless they've already > +been accounted for earlier. A file page will be accounted for as Page Cache; > +it's mapped into the page tables of a process, duplicate accounting is carefully
"," makes run-on sentence...
> +avoided. Page Cache pages are accounted at the time of add_to_page_cache(). > +The corresponding routines that remove a page from the page tables or removes
s/removes/remove/
> +a page from Page Cache is used to decrement the accounting counters of the > +cgroup. > + > +2.3 Shared Page Accounting > + > +Shared pages are accounted on the basis of the first touch approach. The > +cgroup that first touches a page is accounted for the page. The principle > +behind this approach is that a cgroup that aggressively uses a shared > +page will eventually get charged for it (once it is uncharged from > +the cgroup that brought it in -- this will happen on memory pressure). > + > +2.4 Reclaim > + > +Each cgroup maintains a per cgroup LRU that consists of an active > +and inactive list. When a cgroup goes over its limit, we first try > +to reclaim memory from the cgroup so as to make space for the new > +pages that the cgroup has touched. If the reclaim is unsuccessful, > +an OOM routine is invoked to select and kill the bulkiest task in the > +cgroup. > + > +The reclaim algorithm has not been modified for cgroups, except that > +pages that are selected for reclaiming come from the per cgroup LRU > +list. > + > +2. Locking
2. ?? Section numbering is "off."
> +The memory controller uses the following hierarchy > + > +1. zone->lru_lock is used for selecting pages to be isolated > +2. mem->lru_lock protects the per cgroup LRU > +3. lock_page_cgroup() is used to protect page->page_cgroup > + > +3. User Interface > + > +0. Configuration
0. Kernel build configuration > + > +a. Enable CONFIG_CGROUPS > +b. Enable CONFIG_RESOURCE_COUNTERS > +c. Enable CONFIG_CGROUP_MEM_CONT [snip]
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