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author | Paul Mundt <lethal@linux-sh.org> | 2009-09-25 12:15:15 +0900 |
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committer | Paul Mundt <lethal@linux-sh.org> | 2009-09-25 12:15:15 +0900 |
commit | c373ba999103fa794f041eab5bd490714d2dee88 (patch) | |
tree | 8f2b445b1e0af2491c83527967dbcda76054a486 /Documentation/cgroups/memory.txt | |
parent | 6f3529f00a0a9ac06413d18d3926adf099cb59af (diff) | |
parent | 851b147e4411df6a1e7e90e2a609773c277eefd2 (diff) |
Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6
Diffstat (limited to 'Documentation/cgroups/memory.txt')
-rw-r--r-- | Documentation/cgroups/memory.txt | 41 |
1 files changed, 40 insertions, 1 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index 23d1262c077..b871f2552b4 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -179,6 +179,9 @@ The reclaim algorithm has not been modified for cgroups, except that pages that are selected for reclaiming come from the per cgroup LRU list. +NOTE: Reclaim does not work for the root cgroup, since we cannot set any +limits on the root cgroup. + 2. Locking The memory controller uses the following hierarchy @@ -210,6 +213,7 @@ We can alter the memory limit: NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo, mega or gigabytes. NOTE: We can write "-1" to reset the *.limit_in_bytes(unlimited). +NOTE: We cannot set limits on the root cgroup any more. # cat /cgroups/0/memory.limit_in_bytes 4194304 @@ -375,7 +379,42 @@ cgroups created below it. NOTE2: This feature can be enabled/disabled per subtree. -7. TODO +7. Soft limits + +Soft limits allow for greater sharing of memory. The idea behind soft limits +is to allow control groups to use as much of the memory as needed, provided + +a. There is no memory contention +b. They do not exceed their hard limit + +When the system detects memory contention or low memory control groups +are pushed back to their soft limits. If the soft limit of each control +group is very high, they are pushed back as much as possible to make +sure that one control group does not starve the others of memory. + +Please note that soft limits is a best effort feature, it comes with +no guarantees, but it does its best to make sure that when memory is +heavily contended for, memory is allocated based on the soft limit +hints/setup. Currently soft limit based reclaim is setup such that +it gets invoked from balance_pgdat (kswapd). + +7.1 Interface + +Soft limits can be setup by using the following commands (in this example we +assume a soft limit of 256 megabytes) + +# echo 256M > memory.soft_limit_in_bytes + +If we want to change this to 1G, we can at any time use + +# echo 1G > memory.soft_limit_in_bytes + +NOTE1: Soft limits take effect over a long period of time, since they involve + reclaiming memory for balancing between memory cgroups +NOTE2: It is recommended to set the soft limit always below the hard limit, + otherwise the hard limit will take precedence. + +8. TODO 1. Add support for accounting huge pages (as a separate controller) 2. Make per-cgroup scanner reclaim not-shared pages first |