Hello, when using "real" processors the scheduler can make its decisions based on wall time. But CPUs under hypervisor control are sometimes unavailable without further notice to the guest operating system. Using wall time for scheduling decisions in this case will lead to unfair decisions and erroneous distribution of CPU bandwidth when using cgroups. On (at least) S390 every CPU has a timer that counts the real execution time from IPL. When the hypervisor has sheduled out the CPU, the timer is stopped. So it is desirable to use this timer as a source for the scheduler's rq runtime calculations. On SMT systems the consumed runtime of a task might be worth more or less depending on the fact that the task can have run alone or not during the last delta. This should be scalable based on the current CPU utilization. The first patch introduces two little hooks to the optional architecture funtions cpu_exec_time and scale_rq_clock_delta. Calls to cpu_exec_time replace calls to sched_clock_cpu a few times but are mapped back to sched_clock_cpu if architecture does not define cpu_exec_time. The call to scale_rq_clock_delta is added into update_rq_clock (sched/core.c) and defaults to a NOP when not defined by architecture code. Regards Philipp Philipp Hachtmann (3): sched: Support for CPU runtime and SMT based adaption s390/cputime: Provide CPU runtime since IPL s390/cputime: SMT based scaling of CPU runtime deltas arch/s390/include/asm/cputime.h | 31 +++++++++++++++++++++++++++++++ arch/s390/kernel/vtime.c | 4 ++-- kernel/sched/core.c | 4 +++- kernel/sched/fair.c | 8 ++++---- kernel/sched/sched.h | 8 ++++++++ 5 files changed, 48 insertions(+), 7 deletions(-) -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
