linux-kernel - Re: [PATCH] sched/isolation: Make use of more than one housekeeping cpu

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Message-ID: <ffd19f47-dbbb-4b04-82f7-d858b2d0ed64@redhat.com>
Date: Tue, 11 Feb 2025 09:24:25 -0500
From: Waiman Long <llong@...hat.com>
To: Phil Auld <pauld@...hat.com>, linux-kernel@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>, Juri Lelli
 <juri.lelli@...hat.com>, Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH] sched/isolation: Make use of more than one housekeeping
 cpu

On 2/11/25 9:14 AM, Phil Auld wrote:
> Oops, sorry... meant "[PATCH]"
>
> On Tue, Feb 11, 2025 at 02:01:04PM +0000 Phil Auld wrote:
>> The exising code uses housekeeping_any_cpu() to select a cpu for
>> a given housekeeping task. However, this often ends up calling
>> cpumask_any_and() which is defined as cpumask_first_and() which has
>> the effect of alyways using the first cpu among those available.
>>
>> The same applies when multiple NUMA nodes are involved. In that
>> case the first cpu in the local node is chosen which does provide
>> a bit of spreading but with multiple HK cpus per node the same
>> issues arise.
>>
>> Spread the HK work out by having housekeeping_any_cpu() and
>> sched_numa_find_closest() use cpumask_any_and_distribute()
>> instead of cpumask_any_and().
>>
>> Signed-off-by: Phil Auld <pauld@...hat.com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Juri Lelli <juri.lelli@...hat.com>
>> Cc: Frederic Weisbecker <frederic@...nel.org>
>> Cc: Waiman Long <longman@...hat.com>
>> Cc: linux-kernel@...r.kernel.org
>> ---
>>   kernel/sched/isolation.c | 2 +-
>>   kernel/sched/topology.c  | 2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
>> index 81bc8b329ef1..93b038d48900 100644
>> --- a/kernel/sched/isolation.c
>> +++ b/kernel/sched/isolation.c
>> @@ -40,7 +40,7 @@ int housekeeping_any_cpu(enum hk_type type)
>>   			if (cpu < nr_cpu_ids)
>>   				return cpu;
>>   
>> -			cpu = cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask);
>> +			cpu = cpumask_any_and_distribute(housekeeping.cpumasks[type], cpu_online_mask);
>>   			if (likely(cpu < nr_cpu_ids))
>>   				return cpu;
>>   			/*
>> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
>> index c49aea8c1025..94133f843485 100644
>> --- a/kernel/sched/topology.c
>> +++ b/kernel/sched/topology.c
>> @@ -2101,7 +2101,7 @@ int sched_numa_find_closest(const struct cpumask *cpus, int cpu)
>>   	for (i = 0; i < sched_domains_numa_levels; i++) {
>>   		if (!masks[i][j])
>>   			break;
>> -		cpu = cpumask_any_and(cpus, masks[i][j]);
>> +		cpu = cpumask_any_and_distribute(cpus, masks[i][j]);
>>   		if (cpu < nr_cpu_ids) {
>>   			found = cpu;
>>   			break;
>> -- 
>> 2.47.1
>>
>>
LGTM

Reviewed-by: Waiman Long <longman@...hat.com>