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Message-Id: <1356799386-4212-19-git-send-email-fweisbec@gmail.com> Date: Sat, 29 Dec 2012 17:42:57 +0100 From: Frederic Weisbecker <fweisbec@...il.com> To: LKML <linux-kernel@...r.kernel.org> Cc: Frederic Weisbecker <fweisbec@...il.com>, Alessio Igor Bogani <abogani@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Chris Metcalf <cmetcalf@...era.com>, Christoph Lameter <cl@...ux.com>, Geoff Levand <geoff@...radead.org>, Gilad Ben Yossef <gilad@...yossef.com>, Hakan Akkan <hakanakkan@...il.com>, Ingo Molnar <mingo@...nel.org>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, Paul Gortmaker <paul.gortmaker@...driver.com>, Peter Zijlstra <peterz@...radead.org>, Steven Rostedt <rostedt@...dmis.org>, Thomas Gleixner <tglx@...utronix.de> Subject: [PATCH 18/27] sched: Update nohz rq clock before searching busiest group on load balancing While load balancing an rq target, we look for the busiest group. This operation may require an uptodate rq clock if we end up calling scale_rt_power(). To this end, update it manually if the target is running tickless. DOUBT: don't we actually also need this in vanilla kernel, in case this_cpu is in dyntick-idle mode? Signed-off-by: Frederic Weisbecker <fweisbec@...il.com> Cc: Alessio Igor Bogani <abogani@...nel.org> Cc: Andrew Morton <akpm@...ux-foundation.org> Cc: Chris Metcalf <cmetcalf@...era.com> Cc: Christoph Lameter <cl@...ux.com> Cc: Geoff Levand <geoff@...radead.org> Cc: Gilad Ben Yossef <gilad@...yossef.com> Cc: Hakan Akkan <hakanakkan@...il.com> Cc: Ingo Molnar <mingo@...nel.org> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@...driver.com> Cc: Peter Zijlstra <peterz@...radead.org> Cc: Steven Rostedt <rostedt@...dmis.org> Cc: Thomas Gleixner <tglx@...utronix.de> --- kernel/sched/fair.c | 13 +++++++++++++ 1 files changed, 13 insertions(+), 0 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 698137d..473f50f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5023,6 +5023,19 @@ static int load_balance(int this_cpu, struct rq *this_rq, schedstat_inc(sd, lb_count[idle]); + /* + * find_busiest_group() may need an uptodate cpu clock + * for find_busiest_group() (see scale_rt_power()). If + * the CPU is nohz, it's clock may be stale. + */ + if (tick_nohz_full_cpu(this_cpu)) { + local_irq_save(flags); + raw_spin_lock(&this_rq->lock); + update_rq_clock(this_rq); + raw_spin_unlock(&this_rq->lock); + local_irq_restore(flags); + } + redo: group = find_busiest_group(&env, balance); -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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