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-rw-r--r--Documentation/cpusets.txt18
1 files changed, 10 insertions, 8 deletions
diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt
index 1f5a924d1e56..47e568a9370a 100644
--- a/Documentation/cpusets.txt
+++ b/Documentation/cpusets.txt
@@ -635,14 +635,16 @@ prior 'mems' setting, will not be moved.
635 635
636There is an exception to the above. If hotplug functionality is used 636There is an exception to the above. If hotplug functionality is used
637to remove all the CPUs that are currently assigned to a cpuset, 637to remove all the CPUs that are currently assigned to a cpuset,
638then the kernel will automatically update the cpus_allowed of all 638then all the tasks in that cpuset will be moved to the nearest ancestor
639tasks attached to CPUs in that cpuset to allow all CPUs. When memory 639with non-empty cpus. But the moving of some (or all) tasks might fail if
640hotplug functionality for removing Memory Nodes is available, a 640cpuset is bound with another cgroup subsystem which has some restrictions
641similar exception is expected to apply there as well. In general, 641on task attaching. In this failing case, those tasks will stay
642the kernel prefers to violate cpuset placement, over starving a task 642in the original cpuset, and the kernel will automatically update
643that has had all its allowed CPUs or Memory Nodes taken offline. User 643their cpus_allowed to allow all online CPUs. When memory hotplug
644code should reconfigure cpusets to only refer to online CPUs and Memory 644functionality for removing Memory Nodes is available, a similar exception
645Nodes when using hotplug to add or remove such resources. 645is expected to apply there as well. In general, the kernel prefers to
646violate cpuset placement, over starving a task that has had all
647its allowed CPUs or Memory Nodes taken offline.
646 648
647There is a second exception to the above. GFP_ATOMIC requests are 649There is a second exception to the above. GFP_ATOMIC requests are
648kernel internal allocations that must be satisfied, immediately. 650kernel internal allocations that must be satisfied, immediately.