Messages in this thread Patch in this message | | | Date | Thu, 15 Jun 2023 15:25:49 -0700 | Subject | Re: [PATCH v4 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 5/25/2023 11:02 AM, James Morse wrote:
...
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h > index 021a8956518c..9cba8fc405b9 100644 > --- a/arch/x86/kernel/cpu/resctrl/internal.h > +++ b/arch/x86/kernel/cpu/resctrl/internal.h > @@ -79,6 +79,37 @@ static inline unsigned int cpumask_any_housekeeping(const struct cpumask *mask) > return cpu; > } > > +/** > + * cpumask_any_housekeeping_but() - Chose any cpu in @mask, preferring those > + * 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 @but. If there are housekeeping CPUs that
"but not @exclude_cpu"
> + * 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) > +{ > + int cpu, hk_cpu;
Should these be unsigned int?
> + > + cpu = cpumask_any_but(mask, exclude_cpu); > + if (tick_nohz_full_cpu(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); > + } > +
These braces are not necessary. If they are added to help readability then perhaps the indentation can be reduced by using an earlier:
if (!tick_nohz_full_cpu(cpu)) return cpu;
> + 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 +595,13 @@ 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_resource *r, 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 ced933694f60..ae02185f3354 100644 > --- a/arch/x86/kernel/cpu/resctrl/monitor.c > +++ b/arch/x86/kernel/cpu/resctrl/monitor.c > @@ -485,7 +485,7 @@ static void add_rmid_to_limbo(struct rmid_entry *entry) > * setup up the limbo worker. > */ > if (!has_busy_rmid(r, d)) > - cqm_setup_limbo_handler(d, CQM_LIMBOCHECK_INTERVAL); > + cqm_setup_limbo_handler(d, CQM_LIMBOCHECK_INTERVAL, -1);
Should this -1 be RESCTRL_PICK_ANY_CPU?
> set_bit(idx, d->rmid_busy_llc); > entry->busy++; > } > @@ -810,15 +810,28 @@ 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, -1 to pick any CPU.
Should -1 be RESCTRL_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); > - dom->cqm_work_cpu = cpu; > + 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); > > - schedule_delayed_work_on(cpu, &dom->cqm_limbo, delay); > + if (cpu < nr_cpu_ids) { > + dom->cqm_work_cpu = cpu;
Should cqm_work_cpu not perhaps be set to nr_cpu_ids on failure? If it keeps pointing to CPU that ran worker previously there may be unexpected behavior.
Note the different behavior between cqm_setup_limbo_handler() and mbm_setup_overflow_handler() in this regard.
> + schedule_delayed_work_on(cpu, &dom->cqm_limbo, delay); > + } > } > > void mbm_handle_overflow(struct work_struct *work) > @@ -864,7 +877,14 @@ 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, -1 to pick any CPU.
RESCTRL_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; > @@ -875,9 +895,15 @@ 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 == -1)
same
> + 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); > } >
...
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h > index ecd41762d61a..089b91133e5e 100644 > --- a/include/linux/resctrl.h > +++ b/include/linux/resctrl.h > @@ -9,6 +9,9 @@ > /* CLOSID value used by the default control group */ > #define RESCTRL_RESERVED_CLOSID 0 > > +/* Indicates no CPU needs to be excluded */
This comment seems to just be a rewrite of the macro name.
> +#define RESCTRL_PICK_ANY_CPU -1 > + > #ifdef CONFIG_PROC_CPU_RESCTRL > > int proc_resctrl_show(struct seq_file *m,
Reinette
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