linux-kernel - Re: [PATCH 2/3] nvme-pci: limit queue count to housekeeping cpus

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Date: Sun, 23 Jun 2024 10:03:47 +0300
From: Sagi Grimberg <sagi@...mberg.me>
To: Christoph Hellwig <hch@....de>, Daniel Wagner <dwagner@...e.de>
Cc: Jens Axboe <axboe@...nel.dk>, Keith Busch <kbusch@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>,
 Frederic Weisbecker <fweisbecker@...e.com>, Mel Gorman <mgorman@...e.de>,
 Hannes Reinecke <hare@...e.de>,
 Sridhar Balaraman <sbalaraman@...allelwireless.com>,
 "brookxu.cn" <brookxu.cn@...il.com>, Ming Lei <ming.lei@...hat.com>,
 linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
 linux-nvme@...ts.infradead.org
Subject: Re: [PATCH 2/3] nvme-pci: limit queue count to housekeeping cpus



On 22/06/2024 8:14, Christoph Hellwig wrote:
>> diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
>> index 9638b25fd521..43c039900ef6 100644
>> --- a/block/blk-mq-cpumap.c
>> +++ b/block/blk-mq-cpumap.c
>> @@ -11,10 +11,23 @@
>>   #include <linux/smp.h>
>>   #include <linux/cpu.h>
>>   #include <linux/group_cpus.h>
>> +#include <linux/sched/isolation.h>
>>   
>>   #include "blk.h"
>>   #include "blk-mq.h"
>>   
>> +unsigned int blk_mq_num_possible_queues(void)
>> +{
>> +	const struct cpumask *io_queue_mask;
>> +
>> +	io_queue_mask = housekeeping_cpumask(HK_TYPE_IO_QUEUE);
>> +	if (!cpumask_empty(io_queue_mask))
>> +		return cpumask_weight(io_queue_mask);
>> +
>> +	return num_possible_cpus();
>> +}
>> +EXPORT_SYMBOL_GPL(blk_mq_num_possible_queues);
> This should be split into a separate patch.  And it could really use
> a kerneldoc comment.

Agree.

Other than that, looks good.