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author | Suresh Siddha <suresh.b.siddha@intel.com> | 2010-03-31 16:47:45 -0700 |
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committer | Ingo Molnar <mingo@elte.hu> | 2010-04-23 11:02:02 +0200 |
commit | 99bd5e2f245d8cd17d040c82d40becdb3efd9b69 (patch) | |
tree | 9dbfd8d1a9148bad45e5c3c067a05f414134083b /Documentation/ia64 | |
parent | 669c55e9f99b90e46eaa0f98a67ec53d46dc969a (diff) |
sched: Fix select_idle_sibling() logic in select_task_rq_fair()
Issues in the current select_idle_sibling() logic in select_task_rq_fair()
in the context of a task wake-up:
a) Once we select the idle sibling, we use that domain (spanning the cpu that
the task is currently woken-up and the idle sibling that we found) in our
wake_affine() decisions. This domain is completely different from the
domain(we are supposed to use) that spans the cpu that the task currently
woken-up and the cpu where the task previously ran.
b) We do select_idle_sibling() check only for the cpu that the task is
currently woken-up on. If select_task_rq_fair() selects the previously run
cpu for waking the task, doing a select_idle_sibling() check
for that cpu also helps and we don't do this currently.
c) In the scenarios where the cpu that the task is woken-up is busy but
with its HT siblings are idle, we are selecting the task be woken-up
on the idle HT sibling instead of a core that it previously ran
and currently completely idle. i.e., we are not taking decisions based on
wake_affine() but directly selecting an idle sibling that can cause
an imbalance at the SMT/MC level which will be later corrected by the
periodic load balancer.
Fix this by first going through the load imbalance calculations using
wake_affine() and once we make a decision of woken-up cpu vs previously-ran cpu,
then choose a possible idle sibling for waking up the task on.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1270079265.7835.8.camel@sbs-t61.sc.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'Documentation/ia64')
0 files changed, 0 insertions, 0 deletions