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| -rw-r--r-- | Documentation/cgroups/memory.txt | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index 7781857dc94..bac328c232f 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -385,6 +385,10 @@ mapped_file - # of bytes of mapped file (includes tmpfs/shmem) pgpgin - # of pages paged in (equivalent to # of charging events). pgpgout - # of pages paged out (equivalent to # of uncharging events). swap - # of bytes of swap usage +dirty - # of bytes that are waiting to get written back to the disk. +writeback - # of bytes that are actively being written back to the disk. +nfs_unstable - # of bytes sent to the NFS server, but not yet committed to + the actual storage. inactive_anon - # of bytes of anonymous memory and swap cache memory on LRU list. active_anon - # of bytes of anonymous and swap cache memory on active @@ -406,6 +410,9 @@ total_mapped_file - sum of all children's "cache" total_pgpgin - sum of all children's "pgpgin" total_pgpgout - sum of all children's "pgpgout" total_swap - sum of all children's "swap" +total_dirty - sum of all children's "dirty" +total_writeback - sum of all children's "writeback" +total_nfs_unstable - sum of all children's "nfs_unstable" total_inactive_anon - sum of all children's "inactive_anon" total_active_anon - sum of all children's "active_anon" total_inactive_file - sum of all children's "inactive_file" @@ -453,6 +460,73 @@ memory under it will be reclaimed. You can reset failcnt by writing 0 to failcnt file. # echo 0 > .../memory.failcnt +5.5 dirty memory + +Control the maximum amount of dirty pages a cgroup can have at any given time. + +Limiting dirty memory is like fixing the max amount of dirty (hard to reclaim) +page cache used by a cgroup. So, in case of multiple cgroup writers, they will +not be able to consume more than their designated share of dirty pages and will +be forced to perform write-out if they cross that limit. + +The interface is equivalent to the procfs interface: /proc/sys/vm/dirty_*. It +is possible to configure a limit to trigger both a direct writeback or a +background writeback performed by per-bdi flusher threads. The root cgroup +memory.dirty_* control files are read-only and match the contents of +the /proc/sys/vm/dirty_* files. + +Per-cgroup dirty limits can be set using the following files in the cgroupfs: + +- memory.dirty_ratio: the amount of dirty memory (expressed as a percentage of + cgroup memory) at which a process generating dirty pages will itself start + writing out dirty data. + +- memory.dirty_limit_in_bytes: the amount of dirty memory (expressed in bytes) + in the cgroup at which a process generating dirty pages will start itself + writing out dirty data. Suffix (k, K, m, M, g, or G) can be used to indicate + that value is kilo, mega or gigabytes. + + Note: memory.dirty_limit_in_bytes is the counterpart of memory.dirty_ratio. + Only one of them may be specified at a time. When one is written it is + immediately taken into account to evaluate the dirty memory limits and the + other appears as 0 when read. + +- memory.dirty_background_ratio: the amount of dirty memory of the cgroup + (expressed as a percentage of cgroup memory) at which background writeback + kernel threads will start writing out dirty data. + +- memory.dirty_background_limit_in_bytes: the amount of dirty memory (expressed + in bytes) in the cgroup at which background writeback kernel threads will + start writing out dirty data. Suffix (k, K, m, M, g, or G) can be used to + indicate that value is kilo, mega or gigabytes. + + Note: memory.dirty_background_limit_in_bytes is the counterpart of + memory.dirty_background_ratio. Only one of them may be specified at a time. + When one is written it is immediately taken into account to evaluate the dirty + memory limits and the other appears as 0 when read. + +A cgroup may contain more dirty memory than its dirty limit. This is possible +because of the principle that the first cgroup to touch a page is charged for +it. Subsequent page counting events (dirty, writeback, nfs_unstable) are also +counted to the originally charged cgroup. + +Example: If page is allocated by a cgroup A task, then the page is charged to +cgroup A. If the page is later dirtied by a task in cgroup B, then the cgroup A +dirty count will be incremented. If cgroup A is over its dirty limit but cgroup +B is not, then dirtying a cgroup A page from a cgroup B task may push cgroup A +over its dirty limit without throttling the dirtying cgroup B task. + +When use_hierarchy=0, each cgroup has dirty memory usage and limits. +System-wide dirty limits are also consulted. Dirty memory consumption is +checked against both system-wide and per-cgroup dirty limits. + +The current implementation does not enforce per-cgroup dirty limits when +use_hierarchy=1. System-wide dirty limits are used for processes in such +cgroups. Attempts to read memory.dirty_* files return the system-wide +values. Writes to the memory.dirty_* files return error. An enhanced +implementation is needed to check the chain of parents to ensure that no +dirty limit is exceeded. + 6. Hierarchy support The memory controller supports a deep hierarchy and hierarchical accounting. |