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    SubjectRe: [PATCH v7 1/2] nohz: add tick_nohz_full_add_cpus_to() and _remove_cpus_from() APIs
    On Fri, Apr 10, 2015 at 04:53:51PM -0400, Chris Metcalf wrote:
    > The "removes_cpus_from" API is useful, for example, to modify a cpumask
    > to avoid the nohz cores so that interrupts aren't sent to them.
    >
    > Likewise the "add_cpus_to" API is useful to modify a cpumask indicating
    > some special nohz-type functionality so that the nohz cores are
    > automatically added to that set.
    >
    > Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
    > ---
    > v7: no change here, just in part 2/2.
    >
    > v6: I think we may finally have accessor names that are OK
    >
    > v5: (skipped this patch)
    >
    > v4: update accessor names to make them clearer [PeterZ]
    >
    > v3: no change here, just in part 2/2.
    >
    > v2: put the "...set_cpus" API together with the change to
    > init_sched_domains() so that they can go into the timer tree
    > independently of other changes in my tree.
    >
    > include/linux/tick.h | 14 ++++++++++++++
    > 1 file changed, 14 insertions(+)
    >
    > include/linux/tick.h | 14 ++++++++++++++
    > 1 file changed, 14 insertions(+)
    >
    > diff --git a/include/linux/tick.h b/include/linux/tick.h
    > index 9c085dc12ae9..8d1754c0f694 100644
    > --- a/include/linux/tick.h
    > +++ b/include/linux/tick.h
    > @@ -186,6 +186,18 @@ static inline bool tick_nohz_full_cpu(int cpu)
    > return cpumask_test_cpu(cpu, tick_nohz_full_mask);
    > }
    >
    > +static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask)
    > +{
    > + if (tick_nohz_full_enabled())
    > + cpumask_or(mask, mask, tick_nohz_full_mask);
    > +}
    > +
    > +static inline void tick_nohz_full_remove_cpus_from(struct cpumask *mask)
    > +{
    > + if (tick_nohz_full_enabled())
    > + cpumask_andnot(mask, mask, tick_nohz_full_mask);

    I would prefer that you don't introduce new APIs if they aren't used in your
    patchset. It seems that's the case for tick_nohz_full_remove_cpus_from().

    Also we have housekeeping_affine() that affines a task to CPUs outside the
    range of nohz full. In case you still need tick_nohz_full_remove_cpus_from()
    in a further patchset, housekeeping_affine_cpumask() would extend the existing
    naming.

    > +}
    > +
    > extern void __tick_nohz_full_check(void);
    > extern void tick_nohz_full_kick(void);
    > extern void tick_nohz_full_kick_cpu(int cpu);
    > @@ -194,6 +206,8 @@ extern void __tick_nohz_task_switch(struct task_struct *tsk);
    > #else
    > 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) { }
    > +static inline void tick_nohz_full_remove_cpus_from(struct cpumask *mask) { }
    > static inline void __tick_nohz_full_check(void) { }
    > static inline void tick_nohz_full_kick_cpu(int cpu) { }
    > static inline void tick_nohz_full_kick(void) { }
    > --
    > 2.1.2
    >


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