doc: document the relax_domain_level kernel boot argument

Document the kernel boot parameter: relax_domain_level=.
Signed-off-by: NPaul Jackson <pj@sgi.com>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Reviewed-by: NLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Documentation/cpusets.txt

@@ -546,6 +546,9 @@ otherwise initial value -1 that indicates the cpuset has no request.
  ( 4  : search nodes in a chunk of node [on NUMA system] )
  ( 5  : search system wide [on NUMA system] )
 
+The system default is architecture dependent.  The system default
+can be changed using the relax_domain_level= boot parameter.
+
 This file is per-cpuset and affect the sched domain where the cpuset
 belongs to.  Therefore if the flag 'sched_load_balance' of a cpuset
 is disabled, then 'sched_relax_domain_level' have no effect since

Documentation/kernel-parameters.txt

@@ -1679,6 +1679,10 @@ and is between 256 and 4096 characters. It is defined in the file
 			Format: <reboot_mode>[,<reboot_mode2>[,...]]
 			See arch/*/kernel/reboot.c or arch/*/kernel/process.c			
 
+	relax_domain_level=
+			[KNL, SMP] Set scheduler's default relax_domain_level.
+			See Documentation/cpusets.txt.
+
 	reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
 
 	reservetop=	[X86-32]