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author | Takashi Iwai <tiwai@suse.de> | 2009-05-04 16:05:23 +0200 |
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committer | Takashi Iwai <tiwai@suse.de> | 2009-05-04 16:05:23 +0200 |
commit | 8560b9321f9050968f393ce1ec67e47c1a0bd5cf (patch) | |
tree | 658ebb20e4fd5dee840f27103b59da367ff473b1 /Documentation/cgroups/cpuacct.txt | |
parent | 72e31981a4e91f84c5b5e8994f5d25b1cf22b6cf (diff) | |
parent | 6574612fbb34c63117581e68f2231ddce027e41e (diff) |
Merge branch 'fix/asoc' into topic/asoc
Diffstat (limited to 'Documentation/cgroups/cpuacct.txt')
-rw-r--r-- | Documentation/cgroups/cpuacct.txt | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/cgroups/cpuacct.txt b/Documentation/cgroups/cpuacct.txt index bb775fbe43d..8b930946c52 100644 --- a/Documentation/cgroups/cpuacct.txt +++ b/Documentation/cgroups/cpuacct.txt @@ -30,3 +30,21 @@ The above steps create a new group g1 and move the current shell process (bash) into it. CPU time consumed by this bash and its children can be obtained from g1/cpuacct.usage and the same is accumulated in /cgroups/cpuacct.usage also. + +cpuacct.stat file lists a few statistics which further divide the +CPU time obtained by the cgroup into user and system times. Currently +the following statistics are supported: + +user: Time spent by tasks of the cgroup in user mode. +system: Time spent by tasks of the cgroup in kernel mode. + +user and system are in USER_HZ unit. + +cpuacct controller uses percpu_counter interface to collect user and +system times. This has two side effects: + +- It is theoretically possible to see wrong values for user and system times. + This is because percpu_counter_read() on 32bit systems isn't safe + against concurrent writes. +- It is possible to see slightly outdated values for user and system times + due to the batch processing nature of percpu_counter. |