On 12/13/2012 06:11 PM, Vincent Guittot wrote: > On 13 December 2012 03:17, Alex Shi <alex....@intel.com> wrote: >> On 12/12/2012 09:31 PM, Vincent Guittot wrote: >>> During the creation of sched_domain, we define a pack buddy CPU for each CPU >>> when one is available. We want to pack at all levels where a group of CPU >>> can >>> be power gated independently from others. >>> On a system that can't power gate a group of CPUs independently, the flag is >>> set at all sched_domain level and the buddy is set to -1. This is the >>> default >>> behavior. >>> On a dual clusters / dual cores system which can power gate each core and >>> cluster independently, the buddy configuration will be : >>> >>> | Cluster 0 | Cluster 1 | >>> | CPU0 | CPU1 | CPU2 | CPU3 | >>> ----------------------------------- >>> buddy | CPU0 | CPU0 | CPU0 | CPU2 | >>> >>> Small tasks tend to slip out of the periodic load balance so the best place >>> to choose to migrate them is during their wake up. The decision is in O(1) >>> as >>> we only check again one buddy CPU >> >> Just have a little worry about the scalability on a big machine, like on >> a 4 sockets NUMA machine * 8 cores * HT machine, the buddy cpu in whole >> system need care 64 LCPUs. and in your case cpu0 just care 4 LCPU. That >> is different on task distribution decision. > > The buddy CPU should probably not be the same for all 64 LCPU it > depends on where it's worth packing small tasks
Do you have further ideas for buddy cpu on such example? > > Which kind of sched_domain configuration have you for such system ? > and how many sched_domain level have you ? it is general X86 domain configuration. with 4 levels, sibling/core/cpu/numa. > _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
