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 15:58:28 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Babu Moger <babu.moger@....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, pawan.kumar.gupta@...ux.intel.com,
        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

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.

> 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??

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


-- 
 i.