sched/core: Clarify SD_flags comment

The SD_flags 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.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dietmar.eggemann@arm.com
Cc: freedom.tan@mediatek.com
Cc: keita.kobayashi.ym@renesas.com
Cc: mgalbraith@suse.de
Cc: sgurrappadi@nvidia.com
Cc: vincent.guittot@linaro.org
Cc: yuyang.du@intel.com
Link: http://lkml.kernel.org/r/20160815105459.GS6879@twins.programming.kicks-ass.netSigned-off-by: NIngo Molnar <mingo@kernel.org>

kernel/sched/core.c

@@ -6355,12 +6355,18 @@ static int sched_domains_curr_level;
 /*
  * SD_flags allowed in topology descriptions.
  *
+ * These flags are purely descriptive of the topology and do not prescribe
+ * behaviour. Behaviour is artificial and mapped in the below sd_init()
+ * function:
+ *
  *   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:
+ * 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		\