chcpu(8): Document CPU deconfiguring behavior

If architecture supports (de)configuring CPUs, the user should
deconfigure disabled CPUs to prevent performance penalties.

Signed-off-by: Mete Durlu <meted@linux.ibm.com>
(cherry picked from commit 5be86d47ad6d1bbdf6699e7cabc8dc663abfa1d7)

diff --git a/sys-utils/chcpu.8.adoc b/sys-utils/chcpu.8.adoc
index 0b0bcbc5789380d6b5a18f521867eb9aa01d9c1e..f08b5a6abf058d043d2dea29b5ac045cbeaf22f0 100644 (file)
--- a/sys-utils/chcpu.8.adoc
+++ b/sys-utils/chcpu.8.adoc
@@ -39,6 +39,8 @@ Enable the specified CPUs. Enabling a CPU means that the kernel sets it online.
 Deconfigure the specified CPUs. Deconfiguring a CPU means that the hypervisor removes the CPU from the virtual hardware on which the Linux instance runs and returns it to the CPU pool. A CPU must be offline, see *-d*, before it can be deconfigured.
 +
 *chcpu -g* is not supported on IBM z/VM, CPUs are always in a configured state.
++
+if *chcpu -g* is supported, any *disabled* CPUs should be *deconfigured* to inform the hypervisor that these CPUs won't be used, avoiding potential performance penalties.
 
 *-p*, *--dispatch* _mode_::
 Set the CPU dispatching _mode_ (polarization). This option has an effect only if your hardware architecture and hypervisor support CPU polarization. Available _modes_ are: