revert documentaion update for memcg's dirty ratio.
Subjct: Revert memory cgroup dirty_ratio Documentation.
The commit ece72400c2 adds documentation
for memcg's dirty ratio. But the function is not implemented yet.
Remove the documentation for avoiding confusing users.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KAMEZAWA Hiroyuki
Linus Torvalds
parent
52cfd503ad
commit
11ff26c884
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@ -385,10 +385,6 @@ mapped_file - # of bytes of mapped file (includes tmpfs/shmem)
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pgpgin - # of pages paged in (equivalent to # of charging events).
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pgpgout - # of pages paged out (equivalent to # of uncharging events).
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swap - # of bytes of swap usage
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dirty - # of bytes that are waiting to get written back to the disk.
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writeback - # of bytes that are actively being written back to the disk.
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nfs_unstable - # of bytes sent to the NFS server, but not yet committed to
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the actual storage.
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inactive_anon - # of bytes of anonymous memory and swap cache memory on
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LRU list.
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active_anon - # of bytes of anonymous and swap cache memory on active
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@ -410,9 +406,6 @@ total_mapped_file - sum of all children's "cache"
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total_pgpgin - sum of all children's "pgpgin"
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total_pgpgout - sum of all children's "pgpgout"
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total_swap - sum of all children's "swap"
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total_dirty - sum of all children's "dirty"
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total_writeback - sum of all children's "writeback"
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total_nfs_unstable - sum of all children's "nfs_unstable"
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total_inactive_anon - sum of all children's "inactive_anon"
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total_active_anon - sum of all children's "active_anon"
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total_inactive_file - sum of all children's "inactive_file"
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@ -460,73 +453,6 @@ memory under it will be reclaimed.
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You can reset failcnt by writing 0 to failcnt file.
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# echo 0 > .../memory.failcnt
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5.5 dirty memory
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Control the maximum amount of dirty pages a cgroup can have at any given time.
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Limiting dirty memory is like fixing the max amount of dirty (hard to reclaim)
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page cache used by a cgroup. So, in case of multiple cgroup writers, they will
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not be able to consume more than their designated share of dirty pages and will
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be forced to perform write-out if they cross that limit.
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The interface is equivalent to the procfs interface: /proc/sys/vm/dirty_*. It
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is possible to configure a limit to trigger both a direct writeback or a
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background writeback performed by per-bdi flusher threads. The root cgroup
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memory.dirty_* control files are read-only and match the contents of
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the /proc/sys/vm/dirty_* files.
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Per-cgroup dirty limits can be set using the following files in the cgroupfs:
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- memory.dirty_ratio: the amount of dirty memory (expressed as a percentage of
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cgroup memory) at which a process generating dirty pages will itself start
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writing out dirty data.
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- memory.dirty_limit_in_bytes: the amount of dirty memory (expressed in bytes)
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in the cgroup at which a process generating dirty pages will start itself
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writing out dirty data. Suffix (k, K, m, M, g, or G) can be used to indicate
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that value is kilo, mega or gigabytes.
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Note: memory.dirty_limit_in_bytes is the counterpart of memory.dirty_ratio.
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Only one of them may be specified at a time. When one is written it is
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immediately taken into account to evaluate the dirty memory limits and the
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other appears as 0 when read.
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- memory.dirty_background_ratio: the amount of dirty memory of the cgroup
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(expressed as a percentage of cgroup memory) at which background writeback
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kernel threads will start writing out dirty data.
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- memory.dirty_background_limit_in_bytes: the amount of dirty memory (expressed
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in bytes) in the cgroup at which background writeback kernel threads will
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start writing out dirty data. Suffix (k, K, m, M, g, or G) can be used to
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indicate that value is kilo, mega or gigabytes.
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Note: memory.dirty_background_limit_in_bytes is the counterpart of
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memory.dirty_background_ratio. Only one of them may be specified at a time.
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When one is written it is immediately taken into account to evaluate the dirty
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memory limits and the other appears as 0 when read.
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A cgroup may contain more dirty memory than its dirty limit. This is possible
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because of the principle that the first cgroup to touch a page is charged for
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it. Subsequent page counting events (dirty, writeback, nfs_unstable) are also
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counted to the originally charged cgroup.
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Example: If page is allocated by a cgroup A task, then the page is charged to
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cgroup A. If the page is later dirtied by a task in cgroup B, then the cgroup A
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dirty count will be incremented. If cgroup A is over its dirty limit but cgroup
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B is not, then dirtying a cgroup A page from a cgroup B task may push cgroup A
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over its dirty limit without throttling the dirtying cgroup B task.
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When use_hierarchy=0, each cgroup has dirty memory usage and limits.
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System-wide dirty limits are also consulted. Dirty memory consumption is
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checked against both system-wide and per-cgroup dirty limits.
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The current implementation does not enforce per-cgroup dirty limits when
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use_hierarchy=1. System-wide dirty limits are used for processes in such
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cgroups. Attempts to read memory.dirty_* files return the system-wide
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values. Writes to the memory.dirty_* files return error. An enhanced
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implementation is needed to check the chain of parents to ensure that no
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dirty limit is exceeded.
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6. Hierarchy support
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The memory controller supports a deep hierarchy and hierarchical accounting.
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