Messages in this thread | | | Date | Wed, 9 Aug 2023 15:38:54 -0700 | Subject | Re: [PATCH v5 21/24] x86/resctrl: Allow overflow/limbo handlers to be scheduled on any-but cpu | From | Reinette Chatre <> |
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Hi James,
On 7/28/2023 9:42 AM, James Morse wrote: > When a CPU is taken offline resctrl may need to move the overflow or > limbo handlers to run on a different CPU. > > Once the offline callbacks have been split, cqm_setup_limbo_handler() > will be called while the CPU that is going offline is still present > in the cpu_mask. > > Pass the CPU to exclude to cqm_setup_limbo_handler() and > mbm_setup_overflow_handler(). These functions can use a variant of > cpumask_any_but() when selecting the CPU. -1 is used to indicate no CPUs > need excluding. > > A subsequent patch moves these calls to be before CPUs have been removed, > so this exclude_cpus behaviour is temporary. > > Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com> > Signed-off-by: James Morse <james.morse@arm.com> > --- > Changes since v2: > * Rephrased a comment to avoid a two letter bad-word. (we) > * Avoid assigning mbm_work_cpu if the domain is going to be free()d > * Added cpumask_any_housekeeping_but(), I dislike the name > > Changes since v3: > * Marked an explanatory comment as temporary as the subsequent patch is > no longer adjacent. > > Changes since v4: > * Check against RESCTRL_PICK_ANY_CPU instead of -1. > * Leave cqm_work_cpu as nr_cpu_ids when no CPU is available. > * Made cpumask_any_housekeeping_but() more readable. > --- > arch/x86/kernel/cpu/resctrl/core.c | 8 +++-- > arch/x86/kernel/cpu/resctrl/internal.h | 36 ++++++++++++++++++++-- > arch/x86/kernel/cpu/resctrl/monitor.c | 42 +++++++++++++++++++++----- > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 6 ++-- > include/linux/resctrl.h | 2 ++ > 5 files changed, 81 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c > index a694563d3929..d39572a0a3cd 100644 > --- a/arch/x86/kernel/cpu/resctrl/core.c > +++ b/arch/x86/kernel/cpu/resctrl/core.c > @@ -582,12 +582,16 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r) > if (r == &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl) { > if (is_mbm_enabled() && cpu == d->mbm_work_cpu) { > cancel_delayed_work(&d->mbm_over); > - mbm_setup_overflow_handler(d, 0); > + /* > + * temporary: exclude_cpu=-1 as this CPU has already > + * been removed by cpumask_clear_cpu()d > + */ > + mbm_setup_overflow_handler(d, 0, RESCTRL_PICK_ANY_CPU); > } > if (is_llc_occupancy_enabled() && cpu == d->cqm_work_cpu && > has_busy_rmid(d)) { > cancel_delayed_work(&d->cqm_limbo); > - cqm_setup_limbo_handler(d, 0); > + cqm_setup_limbo_handler(d, 0, RESCTRL_PICK_ANY_CPU); > } > } > } > diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h > index f99e0a1f39c8..655418c23c0e 100644 > --- a/arch/x86/kernel/cpu/resctrl/internal.h > +++ b/arch/x86/kernel/cpu/resctrl/internal.h > @@ -79,6 +79,36 @@ static inline unsigned int cpumask_any_housekeeping(const struct cpumask *mask) > return cpu; > } > > +/** > + * cpumask_any_housekeeping_but() - Chose any cpu in @mask, preferring those
cpu -> CPU
> + * that aren't marked nohz_full, excluding > + * the provided CPU > + * @mask: The mask to pick a CPU from. > + * @exclude_cpu:The CPU to avoid picking. > + * > + * Returns a CPU from @mask, but not @exclude_cpus. If there are housekeeping
exclude_cpus -> exclude_cpu
> + * CPUs that don't use nohz_full, these are preferred. > + * Returns >= nr_cpu_ids if no CPUs are available. > + */ > +static inline unsigned int > +cpumask_any_housekeeping_but(const struct cpumask *mask, int exclude_cpu) > +{ > + unsigned int cpu, hk_cpu; > + > + cpu = cpumask_any_but(mask, exclude_cpu); > + if (!tick_nohz_full_cpu(cpu)) > + return cpu; > + > + hk_cpu = cpumask_nth_andnot(0, mask, tick_nohz_full_mask); > + if (hk_cpu == exclude_cpu) > + hk_cpu = cpumask_nth_andnot(1, mask, tick_nohz_full_mask); > + > + if (hk_cpu < nr_cpu_ids) > + cpu = hk_cpu; > + > + return cpu; > +} > + > struct rdt_fs_context { > struct kernfs_fs_context kfc; > bool enable_cdpl2; > @@ -564,11 +594,13 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r, > struct rdt_domain *d, struct rdtgroup *rdtgrp, > int evtid, int first); > void mbm_setup_overflow_handler(struct rdt_domain *dom, > - unsigned long delay_ms); > + unsigned long delay_ms, > + int exclude_cpu); > void mbm_handle_overflow(struct work_struct *work); > void __init intel_rdt_mbm_apply_quirk(void); > bool is_mba_sc(struct rdt_resource *r); > -void cqm_setup_limbo_handler(struct rdt_domain *dom, unsigned long delay_ms); > +void cqm_setup_limbo_handler(struct rdt_domain *dom, unsigned long delay_ms, > + int exclude_cpu); > void cqm_handle_limbo(struct work_struct *work); > bool has_busy_rmid(struct rdt_domain *d); > void __check_limbo(struct rdt_domain *d, bool force_free); > diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c > index c0b1ad8d8f6d..471cdc4e4eae 100644 > --- a/arch/x86/kernel/cpu/resctrl/monitor.c > +++ b/arch/x86/kernel/cpu/resctrl/monitor.c > @@ -493,7 +493,8 @@ static void add_rmid_to_limbo(struct rmid_entry *entry) > * setup up the limbo worker. > */ > if (!has_busy_rmid(d)) > - cqm_setup_limbo_handler(d, CQM_LIMBOCHECK_INTERVAL); > + cqm_setup_limbo_handler(d, CQM_LIMBOCHECK_INTERVAL, > + RESCTRL_PICK_ANY_CPU); > set_bit(idx, d->rmid_busy_llc); > entry->busy++; > } > @@ -816,15 +817,28 @@ void cqm_handle_limbo(struct work_struct *work) > mutex_unlock(&rdtgroup_mutex); > } > > -void cqm_setup_limbo_handler(struct rdt_domain *dom, unsigned long delay_ms) > +/** > + * cqm_setup_limbo_handler() - Schedule the limbo handler to run for this > + * domain. > + * @delay_ms: How far in the future the handler should run. > + * @exclude_cpu: Which CPU the handler should not run on, > + * RESCTRL_PICK_ANY_CPU to pick any CPU. > + */ > +void cqm_setup_limbo_handler(struct rdt_domain *dom, unsigned long delay_ms, > + int exclude_cpu) > { > unsigned long delay = msecs_to_jiffies(delay_ms); > int cpu; > > - cpu = cpumask_any_housekeeping(&dom->cpu_mask); > + if (exclude_cpu == RESCTRL_PICK_ANY_CPU) > + cpu = cpumask_any_housekeeping(&dom->cpu_mask); > + else > + cpu = cpumask_any_housekeeping_but(&dom->cpu_mask, > + exclude_cpu);
Having callers need to do this checking seems unnecessary and makes the code complicated. Can cpumask_any_housekeeping_but() instead be made slightly smarter to handle the case where exclude_cpu == RESCTRL_PICK_ANY_CPU ?
Looks like there is a bit of duplication between cpumask_any_housekeeping() and cpumask_any_housekeeping_but().
> dom->cqm_work_cpu = cpu; > > - schedule_delayed_work_on(cpu, &dom->cqm_limbo, delay); > + if (cpu < nr_cpu_ids) > + schedule_delayed_work_on(cpu, &dom->cqm_limbo, delay); > } > > void mbm_handle_overflow(struct work_struct *work) > @@ -870,7 +884,15 @@ void mbm_handle_overflow(struct work_struct *work) > mutex_unlock(&rdtgroup_mutex); > } > > -void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms) > +/** > + * mbm_setup_overflow_handler() - Schedule the overflow handler to run for this > + * domain. > + * @delay_ms: How far in the future the handler should run. > + * @exclude_cpu: Which CPU the handler should not run on, > + * RESCTRL_PICK_ANY_CPU to pick any CPU. > + */ > +void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms, > + int exclude_cpu) > { > unsigned long delay = msecs_to_jiffies(delay_ms); > int cpu; > @@ -881,9 +903,15 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms) > */ > if (!resctrl_mounted || !resctrl_arch_mon_capable()) > return; > - cpu = cpumask_any_housekeeping(&dom->cpu_mask); > + if (exclude_cpu == RESCTRL_PICK_ANY_CPU) > + cpu = cpumask_any_housekeeping(&dom->cpu_mask); > + else > + cpu = cpumask_any_housekeeping_but(&dom->cpu_mask, > + exclude_cpu); > dom->mbm_work_cpu = cpu; > - schedule_delayed_work_on(cpu, &dom->mbm_over, delay); > + > + if (cpu < nr_cpu_ids) > + schedule_delayed_work_on(cpu, &dom->mbm_over, delay); > } >
Reinette
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