Note: This bug is displayed in read-only format because the product is no longer active in Red Hat Bugzilla.

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Description of problem:

It was found during code review that the kernel always try to migrate timers away from idle CPUs to busy CPUs. Real-time CPUs running dpdk polling threads for example, are busy so they are a great candidate to receive timers from idle CPUs (see get_nohz_timer_target() in the kernel sources).

It is not clear how this problem can affect real-time applications and KVM-RT. However, for real-time and high-performance the best thing is for a timer to always fire in the CPU where it was created.

Version-Release number of selected component (if applicable): tuned-profiles-realtime-2.5.1-6.el7.noarch

Thanks, applied:
https://git.fedorahosted.org/cgit/tuned.git/commit/?id=32ef5d8db01c6b539c5d86cfdd6589537d3625d3

Thanks a lot Jaroslav. I'll let you handle this for RHEL7.3 and later for RHEL7.2-z. But no rush, it's not an urgent issue.

==============================================
Verified in:
    tuned-2.7.1-2.el7.noarch
    tuned-profiles-realtime-2.7.1-2.el7.noarch
PASS
==============================================

# grep timer /usr/lib/tuned/realtime/tuned.conf 
kernel.timer_migration = 0
# sysctl kernel.timer_migration
kernel.timer_migration = 1
# tuned-adm profile realtime
# sysctl kernel.timer_migration
kernel.timer_migration = 0

==============================================
Reproduced in:
    tuned-2.5.1-1.el7.noarch
    tuned-profiles-realtime-2.5.1-1.el7.noarch
FAIL
==============================================

# grep timer /usr/lib/tuned/realtime/tuned.conf 
# sysctl kernel.timer_migration
kernel.timer_migration = 1
# tuned-adm profile realtime
# sysctl kernel.timer_migration
kernel.timer_migration = 1

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, 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://rhn.redhat.com/errata/RHBA-2016-2479.html