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 <frede...@kernel.org> Cc: Chris Metcalf <cmetc...@mellanox.com> Cc: Rik van Riel <r...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Mike Galbraith <efa...@gmx.de> Cc: Ingo Molnar <mi...@kernel.org> Cc: Christoph Lameter <c...@linux.com> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Cc: Wanpeng Li <kernel...@gmail.com> Cc: Luiz Capitulino <lcapitul...@redhat.com> --- Documentation/admin-guide/kernel-parameters.txt | 40 ++++++++++++++++--------- 1 file changed, 26 insertions(+), 14 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6b99c8b..62bc8b5 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1727,20 +1727,32 @@ 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. - <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. + isolcpus= [KNL,SMP] Isolate a given set of CPUs from disturbance. + 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 file "cpuset.sched_load_balance". + 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. + + iucv= [HW,NET] -- 2.7.4