diff options
author | David S. Miller <davem@davemloft.net> | 2009-04-13 14:41:05 -0700 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2009-04-13 14:41:05 -0700 |
commit | 83400207a07584539366f6859362db6872809a12 (patch) | |
tree | fad187f8b3bebf1b387ec42ef8143e6f4e49a256 /Documentation/cgroups/cpuacct.txt | |
parent | 0d489ffb76de0fe804cf06a9d4d11fa7342d74b9 (diff) | |
parent | 80a04d3f2f94fb68b5df05e3ac6697130bc3467a (diff) |
Merge branch 'master' of /home/davem/src/GIT/linux-2.6/
Conflicts:
MAINTAINERS
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 +- It is possible to see slightly outdated values for user and system times + due to the batch processing nature of percpu_counter. |