path: root/Documentation/cgroups/memory.txt
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Diffstat (limited to 'Documentation/cgroups/memory.txt')
1 files changed, 12 insertions, 6 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 44e7ded33448..5e028870ee8a 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -454,21 +454,27 @@ And if you want disable it again:
8.2 Type of charges which can be move
Each bits of move_charge_at_immigrate has its own meaning about what type of
-charges should be moved.
+charges should be moved. But in any cases, it must be noted that an account of
+a page or a swap can be moved only when it is charged to the task's current(old)
+memory cgroup.
bit | what type of charges would be moved ?
0 | A charge of an anonymous page(or swap of it) used by the target task.
| Those pages and swaps must be used only by the target task. You must
| enable Swap Extension(see 2.4) to enable move of swap charges.
-Note: Those pages and swaps must be charged to the old cgroup.
-Note: More type of pages(e.g. file cache, shmem,) will be supported by other
- bits in future.
+ -----+------------------------------------------------------------------------
+ 1 | A charge of file pages(normal file, tmpfs file(e.g. ipc shared memory)
+ | and swaps of tmpfs file) mmaped by the target task. Unlike the case of
+ | anonymous pages, file pages(and swaps) in the range mmapped by the task
+ | will be moved even if the task hasn't done page fault, i.e. they might
+ | not be the task's "RSS", but other task's "RSS" that maps the same file.
+ | And mapcount of the page is ignored(the page can be moved even if
+ | page_mapcount(page) > 1). You must enable Swap Extension(see 2.4) to
+ | enable move of swap charges.
8.3 TODO
-- Add support for other types of pages(e.g. file cache, shmem, etc.).
- Implement madvise(2) to let users decide the vma to be moved or not to be
- All of moving charge operations are done under cgroup_mutex. It's not good