Description of problem: A kernel update was released and the process/thread scheduling adjustments for architectures that can support it seem to either not be included in the kernel, or the kernel is no longer detecting support for them... namely the sysfs entries are now missing: /sys/devices/system/cpu/sched_smt_power_savings, and /sys/devices/system/cpu/sched_mt_power_savings Version-Release number of selected component (if applicable): kernel-PAE-3.5.0-2.fc17.i686 How reproducible: Reproducible at will on machines with Intel Atom CPUs Steps to reproduce: [root@host ~]# ls -la /sys/devices/system/cpu/sched* ls: cannot access /sys/devices/system/cpu/sched*: No such file or directory [root@host ~]# cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 54 model name : Intel(R) Atom(TM) CPU N2800 @ 1.86GHz stepping : 1 microcode : 0x10d cpu MHz : 798.000 cache size : 512 KB physical id : 0 siblings : 4 core id : 0 cpu cores : 2 apicid : 0 initial apicid : 0 fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts nonstop_tsc aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm movbe lahf_lm arat dtherm bogomips : 3733.51 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: . . continues for the 3 other cores/threads . Actual results: shown above. Expected results: the sysfs entries should be present, and i *believe* the "power management" line for the CPUs should be populated.
This was intentionally removed upstream: commit 8e7fbcbc22c12414bcc9dfdd683637f58fb32759 Author: Peter Zijlstra <peterz> Date: Mon Jan 9 11:28:35 2012 +0100 sched: Remove stale power aware scheduling remnants and dysfunctional knobs It's been broken forever (i.e. it's not scheduling in a power aware fashion), as reported by Suresh and others sending patches, and nobody cares enough to fix it properly ... so remove it to make space free for something better. There's various problems with the code as it stands today, first and foremost the user interface which is bound to topology levels and has multiple values per level. This results in a state explosion which the administrator or distro needs to master and almost nobody does. Furthermore large configuration state spaces aren't good, it means the thing doesn't just work right because it's either under so many impossibe to meet constraints, or even if there's an achievable state workloads have to be aware of it precisely and can never meet it for dynamic workloads. So pushing this kind of decision to user-space was a bad idea even with a single knob - it's exponentially worse with knobs on every node of the topology. There is a proposal to replace the user interface with a single 3 state knob: sched_balance_policy := { performance, power, auto } where 'auto' would be the preferred default which looks at things like Battery/AC mode and possible cpufreq state or whatever the hw exposes to show us power use expectations - but there's been no progress on it in the past many months. Aside from that, the actual implementation of the various knobs is known to be broken. There have been sporadic attempts at fixing things but these always stop short of reaching a mergable state. Therefore this wholesale removal with the hopes of spurring people who care to come forward once again and work on a coherent replacement. Signed-off-by: Peter Zijlstra <a.p.zijlstra> Cc: Suresh Siddha <suresh.b.siddha> Cc: Arjan van de Ven <arjan.com> Cc: Vincent Guittot <vincent.guittot> Cc: Vaidyanathan Srinivasan <svaidy.ibm.com> Cc: Linus Torvalds <torvalds> Cc: Andrew Morton <akpm> Link: http://lkml.kernel.org/r/1326104915.2442.53.camel@twins Signed-off-by: Ingo Molnar <mingo>