Messages in this thread | | | From | Peter Williams <> | Date | Fri, 26 May 2006 14:20:21 +1000 | Subject | [RFC 0/5] sched: Add CPU rate caps |
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These patches implement CPU usage rate limits for tasks.
Although the rlimit mechanism already has a CPU usage limit (RLIMIT_CPU) it is a total usage limit and therefore (to my mind) not very useful. These patches provide an alternative whereby the (recent) average CPU usage rate of a task can be limited to a (per task) specified proportion of a single CPU's capacity. The limits are specified in parts per thousand and come in two varieties -- hard and soft. The difference between the two is that the system tries to enforce hard caps regardless of the other demand for CPU resources but allows soft caps to be exceeded if there are spare CPU resources available. By default, tasks will have both caps set to 1000 (i.e. no limit) but newly forked tasks will inherit any caps that have been imposed on their parent from the parent. The mimimim soft cap allowed is 0 (which effectively puts the task in the background) and the minimim hard cap allowed is 1.
Care has been taken to minimize the overhead inflicted on tasks that have no caps and my tests using kernbench indicate that it is hidden in the noise.
Note:
The first patch in this series fixes some problems with priority inheritance that are present in 2.6.17-rc4-mm3 but will be fixed in the next -mm kernel.
Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
-- Peter Williams pwil3058@bigpond.net.au
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