Messages in this thread | | | Date | Thu, 9 Nov 2023 09:48:31 -0800 | Subject | Re: [PATCH v7 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 10/25/2023 11:03 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.
Note "A subsequent patch". Please do go over your entire series. I may not have noticed all.
> > Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com> > Tested-by: Peter Newman <peternewman@google.com> > Reviewed-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. > > Changes since v5: > * Changes in captialisation, and a typo. > * Merged cpumask helpers. > > Changes since v6: > * Added the missing dom parameter to some kernel doc. > * Re-added use of cpumask_any_but(), > * Expanded comment above cpumask_any_housekeeping(), > * Added some more comments for good measure. > * Added explicit IS_ENABLED() check as gcc-12 doesn't seem to work this out. > --- > arch/x86/kernel/cpu/resctrl/core.c | 8 +++-- > arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 2 +- > arch/x86/kernel/cpu/resctrl/internal.h | 33 ++++++++++++++---- > arch/x86/kernel/cpu/resctrl/monitor.c | 42 ++++++++++++++++++----- > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 6 ++-- > include/linux/resctrl.h | 2 ++ > 6 files changed, 72 insertions(+), 21 deletions(-) > > diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c > index 1a74e9c47416..7e44f2c40897 100644 > --- a/arch/x86/kernel/cpu/resctrl/core.c > +++ b/arch/x86/kernel/cpu/resctrl/core.c > @@ -586,12 +586,16 @@ 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/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c > index a033e8e32108..64db51455df3 100644 > --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c > +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c > @@ -552,7 +552,7 @@ void mon_event_read(struct rmid_read *rr, struct rdt_resource *r, > return; > } > > - cpu = cpumask_any_housekeeping(&d->cpu_mask); > + cpu = cpumask_any_housekeeping(&d->cpu_mask, RESCTRL_PICK_ANY_CPU); > > /* > * cpumask_any_housekeeping() prefers housekeeping CPUs, but > diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h > index c4c1e1909058..f5fff2f0d866 100644 > --- a/arch/x86/kernel/cpu/resctrl/internal.h > +++ b/arch/x86/kernel/cpu/resctrl/internal.h > @@ -61,19 +61,36 @@ > * cpumask_any_housekeeping() - Choose any CPU in @mask, preferring those that > * aren't marked nohz_full > * @mask: The mask to pick a CPU from. > + * @exclude_cpu:The CPU to avoid picking. > * > - * Returns a CPU in @mask. If there are housekeeping CPUs that don't use > - * nohz_full, these are preferred. > + * Returns a CPU from @mask, but not @exclude_cpu. If there are housekeeping > + * CPUs that don't use nohz_full, these are preferred. Pass > + * RESCTRL_PICK_ANY_CPU to avoid excluding any CPUs. > + * > + * When a CPU is excluded, returns >= nr_cpu_ids if no CPUs are available. > */ > -static inline unsigned int cpumask_any_housekeeping(const struct cpumask *mask) > +static inline unsigned int > +cpumask_any_housekeeping(const struct cpumask *mask, int exclude_cpu) > { > unsigned int cpu, hk_cpu; > > - cpu = cpumask_any(mask); > - if (!tick_nohz_full_cpu(cpu)) > + if (exclude_cpu == RESCTRL_PICK_ANY_CPU) > + cpu = cpumask_any(mask); > + else > + cpu = cpumask_any_but(mask, exclude_cpu); > + > + if (!IS_ENABLED(CONFIG_NO_HZ_FULL)) > + return cpu;
It is not clear to me how cpumask_any_but() failure is handled.
cpumask_any_but() returns ">= nr_cpu_ids if no cpus set" ...
> + > + /* If the CPU picked isn't marked nohz_full, we're done */
Please don't impersonate code.
> + if (cpu <= nr_cpu_ids && !tick_nohz_full_cpu(cpu)) > return cpu;
Is this intended to be "cpu < nr_cpu_ids"? But that would have code continue ... so maybe it needs explicit error check of cpumask_any_but() failure with an earlier exit?
> > + /* Try to find a CPU that isn't nohz_full to use in preference */ > 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; >
Reinette
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