update Documentation/controller/memory.txt
Documentation updates for memory controller. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by: Balbir Singh <balbir@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -9,8 +9,7 @@ d. Provides a double LRU: global memory pressure causes reclaim from the
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global LRU; a cgroup on hitting a limit, reclaims from the per
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global LRU; a cgroup on hitting a limit, reclaims from the per
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cgroup LRU
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cgroup LRU
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NOTE: Page Cache (unmapped) also includes Swap Cache pages as a subset
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NOTE: Swap Cache (unmapped) is not accounted now.
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and will not be referred to explicitly in the rest of the documentation.
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Benefits and Purpose of the memory controller
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Benefits and Purpose of the memory controller
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@ -144,7 +143,7 @@ list.
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The memory controller uses the following hierarchy
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The memory controller uses the following hierarchy
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1. zone->lru_lock is used for selecting pages to be isolated
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1. zone->lru_lock is used for selecting pages to be isolated
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2. mem->lru_lock protects the per cgroup LRU
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2. mem->per_zone->lru_lock protects the per cgroup LRU (per zone)
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3. lock_page_cgroup() is used to protect page->page_cgroup
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3. lock_page_cgroup() is used to protect page->page_cgroup
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3. User Interface
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3. User Interface
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@ -193,6 +192,15 @@ this file after a write to guarantee the value committed by the kernel.
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The memory.failcnt field gives the number of times that the cgroup limit was
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The memory.failcnt field gives the number of times that the cgroup limit was
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exceeded.
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exceeded.
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The memory.stat file gives accounting information. Now, the number of
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caches, RSS and Active pages/Inactive pages are shown.
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The memory.force_empty gives an interface to drop *all* charges by force.
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# echo -n 1 > memory.force_empty
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will drop all charges in cgroup. Currently, this is maintained for test.
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4. Testing
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4. Testing
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Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11].
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Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11].
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@ -222,11 +230,8 @@ reclaimed.
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A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a
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A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a
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cgroup might have some charge associated with it, even though all
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cgroup might have some charge associated with it, even though all
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tasks have migrated away from it. If some pages are still left, after following
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tasks have migrated away from it. Such charges are automatically dropped at
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the steps listed in sections 4.1 and 4.2, check the Swap Cache usage in
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rmdir() if there are no tasks.
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/proc/meminfo to see if the Swap Cache usage is showing up in the
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cgroups memory.usage_in_bytes counter. A simple test of swapoff -a and
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swapon -a should free any pending Swap Cache usage.
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4.4 Choosing what to account -- Page Cache (unmapped) vs RSS (mapped)?
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4.4 Choosing what to account -- Page Cache (unmapped) vs RSS (mapped)?
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@ -238,15 +243,11 @@ echo -n 1 > memory.control_type
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5. TODO
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5. TODO
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1. Add support for accounting huge pages (as a separate controller)
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1. Add support for accounting huge pages (as a separate controller)
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2. Improve the user interface to accept/display memory limits in KB or MB
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2. Make per-cgroup scanner reclaim not-shared pages first
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rather than pages (since page sizes can differ across platforms/machines).
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3. Teach controller to account for shared-pages
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3. Make cgroup lists per-zone
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4. Start reclamation when the limit is lowered
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4. Make per-cgroup scanner reclaim not-shared pages first
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5. Start reclamation in the background when the limit is
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5. Teach controller to account for shared-pages
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6. Start reclamation when the limit is lowered
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7. Start reclamation in the background when the limit is
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not yet hit but the usage is getting closer
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not yet hit but the usage is getting closer
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8. Create per zone LRU lists per cgroup
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Summary
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Summary
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