> -----Original Message----- > From: linux-kernel-ow...@vger.kernel.org [mailto:linux-kernel- > ow...@vger.kernel.org] On Behalf Of Frederic Weisbecker > Sent: Tuesday, September 1, 2015 7:51 AM > To: Ingo Molnar; Peter Zijlstra > Cc: LKML; Vatika Harlalka; Chris Metcalf; Thomas Gleixner; Preeti U Murthy; > Christoph Lameter; Frederic Weisbecker; Paul E . McKenney > Subject: [PATCH 1/2] nohz: Affine unpinned timers to housekeepers > > From: Vatika Harlalka <vatikaharla...@gmail.com> > > The problem addressed in this patch is about affining unpinned timers. > Adaptive or Full Dynticks CPUs are currently disturbed by unnecessary > jitter due to firing of such timers on them. > > This patch will affine timers to online CPUs which are not full dynticks > in NOHZ_FULL configured systems. It should not introduce overhead in > nohz full off case due to static keys. > > Reviewed-by: Preeti U Murthy <pre...@linux.vnet.ibm.com> > Signed-off by: Vatika Harlalka <vatikaharla...@gmail.com> > Cc: Ingo Molnar <mi...@kernel.org> > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Christoph Lameter <c...@linux.com> > Cc: Thomas Gleixner <t...@linutronix.de> > Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> > Cc: Chris Metcalf <cmetc...@ezchip.com> > Signed-off-by: Frederic Weisbecker <fweis...@gmail.com> > --- > include/linux/tick.h | 9 +++++++++ > kernel/sched/core.c | 7 +++++-- > 2 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/include/linux/tick.h b/include/linux/tick.h > index 48d901f..e312219 100644 > --- a/include/linux/tick.h > +++ b/include/linux/tick.h > @@ -147,11 +147,20 @@ static inline void tick_nohz_full_add_cpus_to(struct > cpumask *mask) > cpumask_or(mask, mask, tick_nohz_full_mask); > } > > +static inline int housekeeping_any_cpu(void) > +{ > + return cpumask_any_and(housekeeping_mask, cpu_online_mask); > +} > + > extern void tick_nohz_full_kick(void); > extern void tick_nohz_full_kick_cpu(int cpu); > extern void tick_nohz_full_kick_all(void); > extern void __tick_nohz_task_switch(void); > #else > +static inline int housekeeping_any_cpu(void) > +{ > + return smp_processor_id(); > +} > static inline bool tick_nohz_full_enabled(void) { return false; } > static inline bool tick_nohz_full_cpu(int cpu) { return false; } > static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { } > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 8b864ec..0902e4d 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -623,18 +623,21 @@ int get_nohz_timer_target(void) > int i, cpu = smp_processor_id(); > struct sched_domain *sd; > > - if (!idle_cpu(cpu)) > + if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu)) > return cpu; > > rcu_read_lock(); > for_each_domain(cpu, sd) { > for_each_cpu(i, sched_domain_span(sd)) { > - if (!idle_cpu(i)) { > + if (!idle_cpu(i) && is_housekeeping_cpu(cpu)) {
Hi, Frederic, sorry for a naive question. Per my understanding, the tick_nohz_full_mask is added to cpu_isolated_map in sched_init_smp(), and the cpu_isolated_map is excluded from sched_domain in init_sched_domains(), so why check here? Thanks --jyh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
