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: 1. This versions incorporates improvements and bug fixes as a result of feedback from an earlier post. Special thanks to Con Kolivas whose suggestions with respect to improved methods for avoiding starvation and priority inversion have enabled cap enforcement to be stricter. 2. This patch is against 2.6.17-rc5-mm2. Signed-off-by: Peter Williams <[EMAIL PROTECTED]> -- Peter Williams [EMAIL PROTECTED] "Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce _______________________________________________ ckrm-tech mailing list https://lists.sourceforge.net/lists/listinfo/ckrm-tech
