* Bart Samwel <[email protected]> [2009-02-11 17:28:25]: > Hi Vaidyanathan, > > Vaidyanathan Srinivasan wrote: >> * Bart Samwel <[email protected]> [2009-02-11 12:21:42]: >> >>> Hi Owen, >>> >>> Owen Gardiner wrote: >>>> I don't know where to go to make changes from your TIPS section >>>> survive reboots. The specific changes are: >>>> >>>> echo 1 > /sys/devices/system/cpu/sched_mc_power_savings >> >> This setting is not included in laptop-mode-tools package because this >> work only for multi-socket system and not relevant for laptops or >> desktops with a single dual-core or quad-core CPU module. > > Actually, I think it is included -- I think I remember adding it. Which > is not very useful if what you are saying is true. Aren't there
Yes, this setting is not useful for single socket system like laptop. On recent kernels (2.6.29-rc), the sysfs entry itself will not be exported if the system has single socket. mc_capable() macro has been changed to this effect. #define mc_capable() (cpus_weight(per_cpu(cpu_core_map, 0)) != nr_cpu_ids) > multicore CPU modules where the cores are more independent, e.g. the > early slap-two-CPUs-in-a-single-package type multicore CPUs? I seem to > remember that the Core 2 duo also allows independent frequency scaling > for the cores, doesn't this setting do anything in that situation? Even if each of the CPUs can have independent freq control, we cannot consolidate more than one task on the 'other' cpu. We need to have a package with more than one CPU so that one package can be filled before using the other package. Like if you have two tasks to run in a two socket dual core system, it may be more efficient to run both the tasks on a single socket and let the other one idle as compared to one task on each socket. Now if you have only one dual core CPU, one task has to run on either of them and there is not much scope for optimisation. The scenario may change if your dual core CPU has hyper-threads. But in that case you would use sched_smt_porwersavings tunable to prefer sibling threads than core to run two tasks and save power. --Vaidy _______________________________________________ Discuss mailing list [email protected] http://mail.lesswatts.org/mailman/listinfo/discuss
