Messages in this thread | | | Date | Thu, 24 Aug 2023 17:57:51 +0100 | Subject | Re: [PATCH v5 21/24] x86/resctrl: Allow overflow/limbo handlers to be scheduled on any-but cpu | From | James Morse <> |
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Hi Reinette,
On 09/08/2023 23:38, Reinette Chatre wrote: > 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.
>> 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
>> @@ -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().
Yup, this was because I was originally going to add them to cpumask.h, but figured it would be easier to leave them here - in a shape that could be moved to cpumask.h if anyone else needs them.
Using one helper for both would simplify things for resctrl, I'll do that.
Thanks,
James
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