diff options
author | Paul Mackerras <paulus@samba.org> | 2009-04-22 13:02:09 +1000 |
---|---|---|
committer | Paul Mackerras <paulus@samba.org> | 2009-04-22 13:02:09 +1000 |
commit | 5bd3ef84d73c2ea7b4babbad060909753c4828d4 (patch) | |
tree | fdf2bafb48ae1ed03175f6c77a7548a181e69ee9 /Documentation/cgroups/cpuacct.txt | |
parent | 0658c16056660886ea2f35c4f038be70a94b1532 (diff) | |
parent | 6d25b688ecc488753af3c9e6f6a9a575b863cf37 (diff) |
Merge branch 'merge' of git://git.secretlab.ca/git/linux-2.6 into merge
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 bb775fbe43d7..8b930946c52a 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 +- It is possible to see slightly outdated values for user and system times + due to the batch processing nature of percpu_counter. |