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Message-ID: <6f90a9c6-d474-4173-9f74-a51675b10e6f@amd.com>
Date: Thu, 9 Nov 2023 14:51:57 -0600
From: "Moger, Babu" <babu.moger@....com>
To: James Morse <james.morse@....com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Cc: Fenghua Yu <fenghua.yu@...el.com>,
Reinette Chatre <reinette.chatre@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
H Peter Anvin <hpa@...or.com>,
shameerali.kolothum.thodi@...wei.com,
D Scott Phillips OS <scott@...amperecomputing.com>,
carl@...amperecomputing.com, lcherian@...vell.com,
bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
dfustini@...libre.com, amitsinght@...vell.com
Subject: Re: [PATCH v7 21/24] x86/resctrl: Allow overflow/limbo handlers to be
scheduled on any-but cpu
On 10/25/23 13:03, 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@...itsu.com>
> Tested-by: Peter Newman <peternewman@...gle.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Signed-off-by: James Morse <james.morse@....com>
Reviewed-by: Babu Moger <babu.moger@....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;
> +
> + /* If the CPU picked isn't marked nohz_full, we're done */
> + if (cpu <= nr_cpu_ids && !tick_nohz_full_cpu(cpu))
> return cpu;
>
> + /* 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;
>
> @@ -575,11 +592,13 @@ 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 87379d2a339c..241b3dd8646c 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -481,7 +481,8 @@ 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++;
> }
> @@ -808,7 +809,8 @@ void cqm_handle_limbo(struct work_struct *work)
> __check_limbo(d, false);
>
> if (has_busy_rmid(d)) {
> - d->cqm_work_cpu = cpumask_any_housekeeping(&d->cpu_mask);
> + d->cqm_work_cpu = cpumask_any_housekeeping(&d->cpu_mask,
> + RESCTRL_PICK_ANY_CPU);
> schedule_delayed_work_on(d->cqm_work_cpu, &d->cqm_limbo,
> delay);
> }
> @@ -816,15 +818,25 @@ 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.
> + * @dom: The domain the limbo handler should run for.
> + * @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);
> + cpu = cpumask_any_housekeeping(&dom->cpu_mask, exclude_cpu);
> 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)
> @@ -862,14 +874,24 @@ void mbm_handle_overflow(struct work_struct *work)
> * Re-check for housekeeping CPUs. This allows the overflow handler to
> * move off a nohz_full CPU quickly.
> */
> - d->mbm_work_cpu = cpumask_any_housekeeping(&d->cpu_mask);
> + d->mbm_work_cpu = cpumask_any_housekeeping(&d->cpu_mask,
> + RESCTRL_PICK_ANY_CPU);
> schedule_delayed_work_on(d->mbm_work_cpu, &d->mbm_over, delay);
>
> out_unlock:
> 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.
> + * @dom: The domain the overflow handler should run for.
> + * @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;
> @@ -880,9 +902,11 @@ 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);
> + cpu = cpumask_any_housekeeping(&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);
> }
>
> static int dom_data_init(struct rdt_resource *r)
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index ab9db7ce706f..e22e0f6adeb3 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -2683,7 +2683,8 @@ static int rdt_get_tree(struct fs_context *fc)
> if (is_mbm_enabled()) {
> r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> list_for_each_entry(dom, &r->domains, list)
> - mbm_setup_overflow_handler(dom, MBM_OVERFLOW_INTERVAL);
> + mbm_setup_overflow_handler(dom, MBM_OVERFLOW_INTERVAL,
> + RESCTRL_PICK_ANY_CPU);
> }
>
> goto out;
> @@ -3994,7 +3995,8 @@ int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d)
>
> if (is_mbm_enabled()) {
> INIT_DELAYED_WORK(&d->mbm_over, mbm_handle_overflow);
> - mbm_setup_overflow_handler(d, MBM_OVERFLOW_INTERVAL);
> + mbm_setup_overflow_handler(d, MBM_OVERFLOW_INTERVAL,
> + RESCTRL_PICK_ANY_CPU);
> }
>
> if (is_llc_occupancy_enabled())
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 4c4bad3c34e4..ccbbbe5d18d3 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -10,6 +10,8 @@
> #define RESCTRL_RESERVED_CLOSID 0
> #define RESCTRL_RESERVED_RMID 0
>
> +#define RESCTRL_PICK_ANY_CPU -1
> +
> #ifdef CONFIG_PROC_CPU_RESCTRL
>
> int proc_resctrl_show(struct seq_file *m,
--
Thanks
Babu Moger
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