On Mon, Aug 15, 2016 at 12:54:59PM +0200, Peter Zijlstra wrote: > On Mon, Jul 25, 2016 at 02:34:22PM +0100, Morten Rasmussen wrote: > > @@ -6336,14 +6338,16 @@ static int sched_domains_curr_level; > > * SD_NUMA - describes NUMA topologies > > * SD_SHARE_POWERDOMAIN - describes shared power domain > > * > > - * Odd one out: > > + * Odd ones out: > > * SD_ASYM_PACKING - describes SMT quirks > > + * SD_ASYM_CPUCAPACITY - describes mixed capacity topologies > > */ > > So I'm not sure the new CPUCAPACITY is 'odd'. > > That said, the comment is very terse and doesn't explain why PACKING is > odd. > > IIRC the distinction is that the 'normal' ones only describe topology, > while the ASYM_PACKING one also prescribes behaviour. It is odd in the > way that it doesn't only describe things. > > This ASYM_CPUCAPACITY otoh is purely descriptive, it doesn't prescribe > how to deal with it.
I think I initially put it in as an 'odd' flag due to the somewhat strange semantics in the previous versions, but now that it is fixed I agree that it belongs together with purely descriptive flags. > > Does something like so clarify things? > > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -6355,13 +6355,19 @@ static int sched_domains_curr_level; > /* > * SD_flags allowed in topology descriptions. > * > - * SD_SHARE_CPUCAPACITY - describes SMT topologies > - * SD_SHARE_PKG_RESOURCES - describes shared caches > - * SD_NUMA - describes NUMA topologies > - * SD_SHARE_POWERDOMAIN - describes shared power domain > + * These flags are purely descriptive of the topology and do not prescribe > + * behaviour. Behaviour is artificial and mapped in the below sd_init() > + * function: > * > - * Odd one out: > - * SD_ASYM_PACKING - describes SMT quirks > + * SD_SHARE_CPUCAPACITY - describes SMT topologies > + * SD_SHARE_PKG_RESOURCES - describes shared caches > + * SD_NUMA - describes NUMA topologies > + * SD_SHARE_POWERDOMAIN - describes shared power domain > + * > + * Odd one out, which beside describing the topology has a quirk also > + * prescribes the desired behaviour that goes along with it: > + * > + * SD_ASYM_PACKING - describes SMT quirks > */ > #define TOPOLOGY_SD_FLAGS \ > (SD_SHARE_CPUCAPACITY | \ I like it :) Morten
