Messages in this thread | | | From | Nathan Lynch <> | Subject | Re: [PATCH v2 1/1] pseries/hotplug-cpu: Change default behaviour of cede_offline to "off" | Date | Thu, 31 Oct 2019 11:30:11 -0500 |
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"Gautham R. Shenoy" <ego@linux.vnet.ibm.com> writes: > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> > > Currently on PSeries Linux guests, the offlined CPU can be put to one > of the following two states: > - Long term processor cede (also called extended cede) > - Returned to the hypervisor via RTAS "stop-self" call. > > This is controlled by the kernel boot parameter "cede_offline=on/off". > > By default the offlined CPUs enter extended cede. The PHYP hypervisor > considers CPUs in extended cede to be "active" since they are still > under the control fo the Linux guests. Hence, when we change the SMT > modes by offlining the secondary CPUs, the PURR and the RWMR SPRs will > continue to count the values for offlined CPUs in extended cede as if > they are online. This breaks the accounting in tools such as lparstat. > > To fix this, ensure that by default the offlined CPUs are returned to > the hypervisor via RTAS "stop-self" call by changing the default value > of "cede_offline_enabled" to false. > > Fixes: commit 3aa565f53c39 ("powerpc/pseries: Add hooks to put the CPU > into an appropriate offline state") > > Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
I'm OK with changing the default as a precursor to removing the code that implements the cede offline mode.
Acked-by: Nathan Lynch <nathanl@linux.ibm.com>
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