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Commit b0d40d2b authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
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sched/isolation: Document isolcpus= boot parameter flags, mark it deprecated 



Document the latest updates on the isolcpus= boot option. While at it,
let's also fix the details about the preferred way to isolate a set of
CPUs from the scheduler general domains. Cpusets offer a much better
interface to achieve that.

Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509419914-16179-1-git-send-email-frederic@kernel.org


[ Clarified the text some more, marked the boot option deprecated. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 150dfee9

Documentation/admin-guide/kernel-parameters.txt

+26 −13
Original line number Diff line number Diff line
@@ -1727,20 +1727,33 @@ 
	isapnp=		[ISAPNP]

			Format: <RDP>,<reset>,<pci_scan>,<verbosity>



	isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.

			The argument is a cpu list, as described above.



			This option can be used to specify one or more CPUs

			to isolate from the general SMP balancing and scheduling

			algorithms. You can move a process onto or off an

			"isolated" CPU via the CPU affinity syscalls or cpuset.

	isolcpus=	[KNL,SMP] Isolate a given set of CPUs from disturbance.

			[Deprecated - use cpusets instead]

			Format: [flag-list,]<cpu-list>



			Specify one or more CPUs to isolate from disturbances

			specified in the flag list (default: domain):



			nohz

			  Disable the tick when a single task runs.

			domain

			  Isolate from the general SMP balancing and scheduling

			  algorithms. Note that performing domain isolation this way

			  is irreversible: it's not possible to bring back a CPU to

			  the domains once isolated through isolcpus. It's strongly

			  advised to use cpusets instead to disable scheduler load

			  balancing through the "cpuset.sched_load_balance" file.

			  It offers a much more flexible interface where CPUs can

			  move in and out of an isolated set anytime.



			  You can move a process onto or off an "isolated" CPU via

			  the CPU affinity syscalls or cpuset.

			  <cpu number> begins at 0 and the maximum value is

			  "number of CPUs in system - 1".



			This option is the preferred way to isolate CPUs. The

			alternative -- manually setting the CPU mask of all

			tasks in the system -- can cause problems and

			suboptimal load balancer performance.

			The format of <cpu-list> is described above.







	iucv=		[HW,NET]