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.
Reviewed-by: Shaopeng Tan <[email protected]>
Tested-by: Shaopeng Tan <[email protected]>
Tested-By: Peter Newman <[email protected]>
Signed-off-by: James Morse <[email protected]>
---
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.
---
arch/x86/kernel/cpu/resctrl/core.c | 8 +++--
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 2 +-
arch/x86/kernel/cpu/resctrl/internal.h | 19 +++++++++---
arch/x86/kernel/cpu/resctrl/monitor.c | 38 +++++++++++++++++------
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 6 ++--
include/linux/resctrl.h | 2 ++
6 files changed, 56 insertions(+), 19 deletions(-)
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 5b4c719ac129..37aa124f1e4c 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/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index ce4821ea111b..b4ed4e1b4938 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 c54fa86e4ef9..bd7f60bf49fe 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -60,11 +60,15 @@
* 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.
+ * 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;
@@ -73,6 +77,9 @@ static inline unsigned int cpumask_any_housekeeping(const struct cpumask *mask)
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;
@@ -565,11 +572,13 @@ 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 9c6d4b0970e2..208e46ba7368 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -480,7 +480,8 @@ 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++;
}
@@ -807,22 +808,31 @@ void cqm_handle_limbo(struct work_struct *work)
__check_limbo(d, false);
if (has_busy_rmid(d)) {
- cpu = cpumask_any_housekeeping(&d->cpu_mask);
+ cpu = cpumask_any_housekeeping(&d->cpu_mask, RESCTRL_PICK_ANY_CPU);
schedule_delayed_work_on(cpu, &d->cqm_limbo, delay);
}
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);
+ 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)
@@ -861,14 +871,22 @@ 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.
*/
- cpu = cpumask_any_housekeeping(&d->cpu_mask);
+ cpu = cpumask_any_housekeeping(&d->cpu_mask, RESCTRL_PICK_ANY_CPU);
schedule_delayed_work_on(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.
+ * @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;
@@ -879,9 +897,11 @@ 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 0c609cdfe7e5..49f100c73838 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2552,7 +2552,8 @@ 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;
@@ -3850,7 +3851,8 @@ 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 9d5f75a4e192..0888d1975161 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,
--
2.39.2
Hi James,
On 9/14/2023 10:21 AM, James Morse wrote:
...
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index c54fa86e4ef9..bd7f60bf49fe 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -60,11 +60,15 @@
> * 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.
> + * Returns >= nr_cpu_ids if no CPUs are available.
It may be helpful to add that the function can only fail if exclude_cpu is
*not* RESCTRL_PICK_ANY_CPU. That helps to understand the sparse error checking.
> */
> -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;
>
> @@ -73,6 +77,9 @@ static inline unsigned int cpumask_any_housekeeping(const struct cpumask *mask)
> return cpu;
>
It is not obvious from this hunk but I cannot see how this would work
on a system without any nohz_full CPUs.
At this point the function looks like:
cpu = cpumask_any(mask);
if (!tick_nohz_full_cpu(cpu))
return cpu;
I expected exclude_cpu to be taken into account. If I understand correctly
exclude_cpu can be picked by cpumask_any() and as long as it is not
a nohz_full CPU it would be returned.
> 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;
>
> @@ -565,11 +572,13 @@ 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 9c6d4b0970e2..208e46ba7368 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -480,7 +480,8 @@ 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++;
> }
> @@ -807,22 +808,31 @@ void cqm_handle_limbo(struct work_struct *work)
> __check_limbo(d, false);
>
> if (has_busy_rmid(d)) {
> - cpu = cpumask_any_housekeeping(&d->cpu_mask);
> + cpu = cpumask_any_housekeeping(&d->cpu_mask, RESCTRL_PICK_ANY_CPU);
> schedule_delayed_work_on(cpu, &d->cqm_limbo, delay);
> }
>
> 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.
> + */
arch/x86/kernel/cpu/resctrl/monitor.c:824: info: Scanning doc for function cqm_setup_limbo_handler
arch/x86/kernel/cpu/resctrl/monitor.c:832: warning: Function parameter or member 'dom' not described in 'cqm_setup_limbo_handler'
> +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)
> @@ -861,14 +871,22 @@ 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.
> */
> - cpu = cpumask_any_housekeeping(&d->cpu_mask);
> + cpu = cpumask_any_housekeeping(&d->cpu_mask, RESCTRL_PICK_ANY_CPU);
> schedule_delayed_work_on(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.
> + * @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.
> + */
arch/x86/kernel/cpu/resctrl/monitor.c:887: info: Scanning doc for function mbm_setup_overflow_handler
arch/x86/kernel/cpu/resctrl/monitor.c:895: warning: Function parameter or member 'dom' not described in 'mbm_setup_overflow_handler'
> +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;
> @@ -879,9 +897,11 @@ 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 0c609cdfe7e5..49f100c73838 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -2552,7 +2552,8 @@ 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;
> @@ -3850,7 +3851,8 @@ 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 9d5f75a4e192..0888d1975161 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,
Reinette
Hi Reinette,
On 03/10/2023 22:22, Reinette Chatre wrote:
> On 9/14/2023 10:21 AM, James Morse wrote:
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>> index c54fa86e4ef9..bd7f60bf49fe 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -60,11 +60,15 @@
>> * 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.
>> + * Returns >= nr_cpu_ids if no CPUs are available.
> It may be helpful to add that the function can only fail if exclude_cpu is
> *not* RESCTRL_PICK_ANY_CPU. That helps to understand the sparse error checking.
Assuming you don't give it an empty mask, that should be true ... but I've missed a
difference between the two helpers use of cpumask_any() when combining them....
It now looks like this:
|/**
| * 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 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, int exclude_cpu)
|{
| unsigned int cpu, hk_cpu;
|
| if (exclude_cpu == RESCTRL_PICK_ANY_CPU)
| cpu = cpumask_any(mask);
| else
| cpu = cpumask_any_but(mask, exclude_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;
|
| return cpu;
|}
This also has to check cpu is in range before passing it to tick_nohz_full_cpu().
>> @@ -73,6 +77,9 @@ static inline unsigned int cpumask_any_housekeeping(const struct cpumask *mask)
>> return cpu;
>>
>
> It is not obvious from this hunk but I cannot see how this would work
> on a system without any nohz_full CPUs.
>
> At this point the function looks like:
>
> cpu = cpumask_any(mask);
> if (!tick_nohz_full_cpu(cpu))
> return cpu;
>
> I expected exclude_cpu to be taken into account. If I understand correctly
> exclude_cpu can be picked by cpumask_any() and as long as it is not
> a nohz_full CPU it would be returned.
Yup, I missed this when combining the functions, fixed as above...
>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
>> index 9c6d4b0970e2..208e46ba7368 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -807,22 +808,31 @@ void cqm_handle_limbo(struct work_struct *work)
>> __check_limbo(d, false);
>>
>> if (has_busy_rmid(d)) {
>> - cpu = cpumask_any_housekeeping(&d->cpu_mask);
>> + cpu = cpumask_any_housekeeping(&d->cpu_mask, RESCTRL_PICK_ANY_CPU);
>> schedule_delayed_work_on(cpu, &d->cqm_limbo, delay);
>> }
>>
>> 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.
>> + */
> arch/x86/kernel/cpu/resctrl/monitor.c:824: info: Scanning doc for function cqm_setup_limbo_handler
> arch/x86/kernel/cpu/resctrl/monitor.c:832: warning: Function parameter or member 'dom' not described in 'cqm_setup_limbo_handler'
What tool outputs this? I've run 'make ARCH=x86 htmldocs', which outputs a tonne of stuff,
but I've never found lines about resctrl in there:
| morse@eglon:~/kernel/mpam/build_x86_64$ make ARCH=x86 htmldocs &> tee output.log
| morse@eglon:~/kernel/mpam/build_x86_64$ cat output.log | grep resctrl
| morse@eglon:~/kernel/mpam/build_x86_64$
Thanks,
James
On 10/25/2023 10:57 AM, James Morse wrote:
> On 03/10/2023 22:22, Reinette Chatre wrote:
...
>
>> arch/x86/kernel/cpu/resctrl/monitor.c:824: info: Scanning doc for function cqm_setup_limbo_handler
>> arch/x86/kernel/cpu/resctrl/monitor.c:832: warning: Function parameter or member 'dom' not described in 'cqm_setup_limbo_handler'
>
> What tool outputs this? I've run 'make ARCH=x86 htmldocs', which outputs a tonne of stuff,
> but I've never found lines about resctrl in there:
> | morse@eglon:~/kernel/mpam/build_x86_64$ make ARCH=x86 htmldocs &> tee output.log
> | morse@eglon:~/kernel/mpam/build_x86_64$ cat output.log | grep resctrl
> | morse@eglon:~/kernel/mpam/build_x86_64$
>
(copied from Documentation/doc-guide/kernel-doc.rst:)
scripts/kernel-doc -v -none drivers/foo/bar.c
Reinette