Messages in this thread | | | From | Frederic Weisbecker <> | Subject | [RFC PATCH 0/3] nohz: Move nohz kick out of scheduler IPI | Date | Wed, 19 Mar 2014 19:28:19 +0100 |
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When a full dynticks CPU runs in single task mode then a new task gets enqueued, we notify it through an IPI such that it restarts its tick.
The IPI used here is the scheduler IPI. There are a few reasons for that: it can be called when interrupts are disabled, it can be called concurrently... These properties altogether aren't offered by the IPI subsystem.
Meanwhile, bloating that way the scheduler IPI with scheduler unrelated code is an abuse of this fast path. We certainly don't want to start a big kernel IPI (BKI, the new shiny piece of my collection of big kernel things aside the big kernel tick, the big reiserfs lock, ..).
So this patchset adds a small helper to the IPI subsystem that allows to queue an IPI from interrupt disabled code and handles concurrent callers as well. Eventually the nohz kick gets converted to this new facility.
Partly inspired by a suggestion from Peter Zijlstra.
Comments?
git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git nohz/ipi
Thanks, Frederic ---
Frederic Weisbecker (3): smp: Non busy-waiting IPI queue nohz: Move full nohz kick to its own IPI nohz: Use IPI implicit full barrier against rq->nr_running r/w
include/linux/smp.h | 12 ++++++++++++ include/linux/tick.h | 2 ++ kernel/sched/core.c | 14 ++++++-------- kernel/sched/sched.h | 12 +++++++++--- kernel/smp.c | 24 ++++++++++++++++++++++++ kernel/time/tick-sched.c | 20 ++++++++++++++++++++ 6 files changed, 73 insertions(+), 11 deletions(-)
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