Messages in this thread Patch in this message | | | From | Balbir Singh <> | Date | Sun, 16 Mar 2008 23:00:17 +0530 | Subject | [RFC][3/3] Update documentation for virtual address space control |
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This patch adds documentation for virtual address space control.
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> ---
Documentation/controllers/memory.txt | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-)
diff -puN Documentation/controllers/memory.txt~memory-controller-virtual-address-control-documentation Documentation/controllers/memory.txt --- linux-2.6.25-rc5/Documentation/controllers/memory.txt~memory-controller-virtual-address-control-documentation 2008-03-16 22:57:44.000000000 +0530 +++ linux-2.6.25-rc5-balbir/Documentation/controllers/memory.txt 2008-03-16 22:57:44.000000000 +0530 @@ -237,7 +237,31 @@ cgroup might have some charge associated tasks have migrated away from it. Such charges are automatically dropped at rmdir() if there are no tasks. -5. TODO +5. Virtual address space accounting + +A new resource counter controls the address space expansion of the tasks in +the cgroup. Address space control is provided along the same lines as +RLIMIT_AS control, which is available via getrlimit(2)/setrlimit(2). +The interface for controlling address space is provided through +"as_limit_in_bytes". The file is similar to "limit_in_bytes" w.r.t the user +interface. Please see section 3 for more details on how to use the user +interface to get and set values. + +The "as_usage_in_bytes" file provides information about the total address +space usage of the cgroup in bytes. + +5.1 Advantages of providing this feature + +1. Control over virtual address space allows for a cgroup to fail gracefully + i.e, via a malloc or mmap failure as compared to OOM kill when no + pages can be reclaimed +2. It provides better control over how many pages can be swapped out when + the cgroup goes over it's limit. A badly setup cgroup can cause excessive + swapping. Providing control over the address space allocations ensures + that the system administrator has control over the total swapping that + can take place. + +6. TODO 1. Add support for accounting huge pages (as a separate controller) 2. Make per-cgroup scanner reclaim not-shared pages first _ -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL
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