cpuset, isolcpus: document relationship between cpusets & isolcpus
Document the subtly changed relationship between cpusets and isolcpus.
Turns out the old documentation did not match the code...
Signed-off-by: Rik van Riel <riel@redhat.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/Documentation/cgroups/cpusets.txt b/Documentation/cgroups/cpusets.txt
index f2235a1..fdf7dff 100644
--- a/Documentation/cgroups/cpusets.txt
+++ b/Documentation/cgroups/cpusets.txt
@@ -392,8 +392,10 @@
than one big one, but doing so means that overloads in one of the
two domains won't be load balanced to the other one.
-By default, there is one sched domain covering all CPUs, except those
-marked isolated using the kernel boot time "isolcpus=" argument.
+By default, there is one sched domain covering all CPUs, including those
+marked isolated using the kernel boot time "isolcpus=" argument. However,
+the isolated CPUs will not participate in load balancing, and will not
+have tasks running on them unless explicitly assigned.
This default load balancing across all CPUs is not well suited for
the following two situations:
@@ -465,6 +467,10 @@
constrained to some subset of the CPUs allowed to them, for lack of
load balancing to the other CPUs.
+CPUs in "cpuset.isolcpus" were excluded from load balancing by the
+isolcpus= kernel boot option, and will never be load balanced regardless
+of the value of "cpuset.sched_load_balance" in any cpuset.
+
1.7.1 sched_load_balance implementation details.
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