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Description of problem:
A customer (AltioStar, this is related to bz1886312) asked for clarifications about
lru-add-drain kthread. They were worried that it might cause latency spikes on isolated
cpus, as its affinity cannot be restricted to non-isolated cpus.
Investigation showed that, on RT kernel, this kthread is allocated (by the workqueue
subsystem), but never actually used since RT kernel doesn't use workqueues to perform
remote_lru_add_drain.
Even though there is practically no harm in creating such kthread, it would be good to
remove it as it creates confusion (at least).
Version-Release number of selected component (if applicable):
kernel-rt-3.10.0-1160.7.1.rt56.1140.el7
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory (Important: kernel-rt security and bug fix update), and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2021:2316