linux-kernel - Re: [PATCH v4 1/7] x86/resctrl: Add multiple tasks to the resctrl group at once

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Date:   Wed, 19 Apr 2023 09:52:11 -0500
From:   "Moger, Babu" <babu.moger@....com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     corbet@....net, Reinette Chatre <reinette.chatre@...el.com>,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        fenghua.yu@...el.com, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, paulmck@...nel.org, akpm@...ux-foundation.org,
        quic_neeraju@...cinc.com, rdunlap@...radead.org,
        damien.lemoal@...nsource.wdc.com, songmuchun@...edance.com,
        peterz@...radead.org, jpoimboe@...nel.org, pbonzini@...hat.com,
        chang.seok.bae@...el.com, pawan.kumar.gupta@...ux.intel.com,
        jmattson@...gle.com, daniel.sneddon@...ux.intel.com,
        sandipan.das@....com, tony.luck@...el.com, james.morse@....com,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        bagasdotme@...il.com, eranian@...gle.com,
        christophe.leroy@...roup.eu, jarkko@...nel.org,
        adrian.hunter@...el.com, quic_jiles@...cinc.com,
        peternewman@...gle.com
Subject: Re: [PATCH v4 1/7] x86/resctrl: Add multiple tasks to the resctrl
 group at once

Hi Jarvinen,

On 4/19/23 07:58, Ilpo Järvinen wrote:
> On Mon, 17 Apr 2023, Babu Moger wrote:
> 
>> The resctrl task assignment for MONITOR or CONTROL group needs to be
>> done one at a time. For example:
>>
>>   $mount -t resctrl resctrl /sys/fs/resctrl/
>>   $mkdir /sys/fs/resctrl/clos1
>>   $echo 123 > /sys/fs/resctrl/clos1/tasks
>>   $echo 456 > /sys/fs/resctrl/clos1/tasks
>>   $echo 789 > /sys/fs/resctrl/clos1/tasks
>>
>> This is not user-friendly when dealing with hundreds of tasks.
>>
>> It can be improved by supporting the multiple task id assignment in
>> one command with the tasks separated by commas. For example:
>>
>>   $echo 123,456,789 > /sys/fs/resctrl/clos1/tasks
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>>  Documentation/x86/resctrl.rst          |    9 ++++++++-
>>  arch/x86/kernel/cpu/resctrl/rdtgroup.c |   31 ++++++++++++++++++++++++++++++-
>>  2 files changed, 38 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/x86/resctrl.rst b/Documentation/x86/resctrl.rst
>> index 387ccbcb558f..f28ed1443a6a 100644
>> --- a/Documentation/x86/resctrl.rst
>> +++ b/Documentation/x86/resctrl.rst
>> @@ -292,7 +292,14 @@ All groups contain the following files:
>>  "tasks":
>>  	Reading this file shows the list of all tasks that belong to
>>  	this group. Writing a task id to the file will add a task to the
>> -	group. If the group is a CTRL_MON group the task is removed from
>> +	group. Multiple tasks can be added by separating the task ids
>> +	with commas. Tasks will be assigned sequentially in the order it
>> +	is entered.
> 
> "Tasks ... it is ..." doesn't sound correct.

How about "Tasks will be assigned sequentially in the order they are entered."

> 
>> Failures while assigning the tasks will be aborted
>> +	immediately and tasks next in the sequence will not be assigned.
>> +	Users may need to retry them again. Failure details possibly with
>> +	pid will be logged in /sys/fs/resctrl/info/last_cmd_status file.
>> +
>> +	If the group is a CTRL_MON group the task is removed from
>>  	whichever previous CTRL_MON group owned the task and also from
>>  	any MON group that owned the task. If the group is a MON group,
>>  	then the task must already belong to the CTRL_MON parent of this
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 6ad33f355861..df5bd13440b0 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -696,18 +696,41 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
>>  				    char *buf, size_t nbytes, loff_t off)
>>  {
>>  	struct rdtgroup *rdtgrp;
>> +	char *pid_str;
>>  	int ret = 0;
>>  	pid_t pid;
>>  
>> -	if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
>> +	if (nbytes == 0)
>>  		return -EINVAL;
>> +
>> +	buf[nbytes - 1] = '\0';
>> +
>>  	rdtgrp = rdtgroup_kn_lock_live(of->kn);
>>  	if (!rdtgrp) {
>>  		rdtgroup_kn_unlock(of->kn);
>>  		return -ENOENT;
>>  	}
>> +
>> +next:
>> +	if (!buf || buf[0] == '\0')
>> +		goto unlock;
>> +
>>  	rdt_last_cmd_clear();
>>  
>> +	pid_str = strim(strsep(&buf, ","));
>> +
>> +	if (kstrtoint(pid_str, 0, &pid)) {
>> +		rdt_last_cmd_printf("Task list parsing error\n");
>> +		ret = -EINVAL;
>> +		goto unlock;
>> +	}
>> +
>> +	if (pid < 0) {
>> +		rdt_last_cmd_printf("Invalid pid %d value\n", pid);
>> +		ret = -EINVAL;
>> +		goto unlock;
>> +	}
>> +
>>  	if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED ||
>>  	    rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
>>  		ret = -EINVAL;
>> @@ -716,6 +739,12 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
>>  	}
>>  
>>  	ret = rdtgroup_move_task(pid, rdtgrp, of);
>> +	if (ret) {
>> +		rdt_last_cmd_printf("Error while processing task %d\n", pid);
>> +		goto unlock;
>> +	} else {
>> +		goto next;
>> +	}
> 
> Why is this not changed into a while () loop??

Yes. I can change that. It might look bit more cleaner.

> 
>>  
>>  unlock:
>>  	rdtgroup_kn_unlock(of->kn);
>>
>>
> 
> 

-- 
Thanks
Babu Moger