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sched/isolation: Document isolcpus= boot parameter flags, mark it deprecated

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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: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Frederic Weisbecker 2017-10-31 04:18:34 +01:00 committed by Ingo Molnar
parent 150dfee95f
commit b0d40d2b22
1 changed files with 25 additions and 12 deletions
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37
Documentation/admin-guide/kernel-parameters.txt
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@ -1727,20 +1727,33 @@
isapnp= [ISAPNP] isapnp= [ISAPNP]
Format: <RDP>,<reset>,<pci_scan>,<verbosity> Format: <RDP>,<reset>,<pci_scan>,<verbosity>
isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. isolcpus= [KNL,SMP] Isolate a given set of CPUs from disturbance.
The argument is a cpu list, as described above. [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".
The format of <cpu-list> is 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.
<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.
iucv= [HW,NET] iucv= [HW,NET]