linux-kernel - Re: [PATCH 2/5] cgroup/cpuset: Add new cpus.partition type with no load balancing

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Date:   Wed, 16 Jun 2021 22:57:18 -0400
From:   Waiman Long <llong@...hat.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <shuah@...nel.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Phil Auld <pauld@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>
Subject: Re: [PATCH 2/5] cgroup/cpuset: Add new cpus.partition type with no
 load balancing

On 6/16/21 4:47 PM, Tejun Heo wrote:
> Hello,
>
> Generally looks fine to me.
>
> On Thu, Jun 03, 2021 at 05:24:13PM -0400, Waiman Long wrote:
>> @@ -1984,12 +1987,31 @@ static int update_prstate(struct cpuset *cs, int val)
>>   			goto out;
>>   
>>   		err = update_parent_subparts_cpumask(cs, partcmd_enable,
>> -						     NULL, &tmp);
>> +						     NULL, &tmpmask);
>> +
>>   		if (err) {
>>   			update_flag(CS_CPU_EXCLUSIVE, cs, 0);
>>   			goto out;
>> +		} else if (new_prs == PRS_ENABLED_NOLB) {
>> +			/*
>> +			 * Disable the load balance flag should not return an
>                                   ^ing
>
> and "else if" after "if (err) goto out" block is weird. The two conditions
> don't need to be tied together.

Yes, the else part is redundant in this case. Will remove it.


>
>> @@ -2518,6 +2547,9 @@ static int sched_partition_show(struct seq_file *seq, void *v)
>>   	case PRS_ENABLED:
>>   		seq_puts(seq, "root\n");
>>   		break;
>> +	case PRS_ENABLED_NOLB:
>> +		seq_puts(seq, "root-nolb\n");
>> +		break;
>>   	case PRS_DISABLED:
>>   		seq_puts(seq, "member\n");
>>   		break;
>> @@ -2544,6 +2576,8 @@ static ssize_t sched_partition_write(struct kernfs_open_file *of, char *buf,
>>   		val = PRS_ENABLED;
>>   	else if (!strcmp(buf, "member"))
>>   		val = PRS_DISABLED;
>> +	else if (!strcmp(buf, "root-nolb"))
>> +		val = PRS_ENABLED_NOLB;
>>   	else
>>   		return -EINVAL;
> I wonder whether there's a better name than "root-nolb" because nolb isn't
> the most readable and we are using space as the delimiter for other names.
> Would something like "isolated" work?

Right. "isolated" is a better name and it corresponds better with the 
isolcpus kernel command line option. Will change the name.

Thanks,
Longman