linux-kernel - Re: [PATCH v8 1/8] x86/resctrl: Add multiple tasks to the resctrl group at once

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Message-ID: <fda1fea1-5e39-8a54-ab97-78d182c54801@amd.com>
Date:   Wed, 6 Sep 2023 09:56:55 -0500
From:   "Moger, Babu" <bmoger@....com>
To:     Fenghua Yu <fenghua.yu@...el.com>, Babu Moger <babu.moger@....com>,
        corbet@....net, reinette.chatre@...el.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de
Cc:     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, 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 v8 1/8] x86/resctrl: Add multiple tasks to the resctrl
 group at once

Hi Fenghua,

On 9/1/2023 5:13 PM, Fenghua Yu wrote:
> Hi, Babu,
>
> On 8/21/23 16:30, 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/ctrl_grp1
>>    $echo 123 > /sys/fs/resctrl/ctrl_grp1/tasks
>>    $echo 456 > /sys/fs/resctrl/ctrl_grp1/tasks
>>    $echo 789 > /sys/fs/resctrl/ctrl_grp1/tasks
>>
>> This is not user-friendly when dealing with hundreds of tasks.
>>
>> Support multiple task assignment in one command with tasks ids separated
>> by commas. For example:
>>    $echo 123,456,789 > /sys/fs/resctrl/ctrl_grp1/tasks
>>
>> Reviewed-by: Tan Shaopeng <tan.shaopeng@...fujitsu.com>
>> Tested-by: Tan Shaopeng <tan.shaopeng@...fujitsu.com>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
>> ---
>>   Documentation/arch/x86/resctrl.rst     |  8 +++++++-
>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 25 ++++++++++++++++++++++---
>>   2 files changed, 29 insertions(+), 4 deletions(-)
>>
>> diff --git a/Documentation/arch/x86/resctrl.rst 
>> b/Documentation/arch/x86/resctrl.rst
>> index cb05d90111b4..af234681756e 100644
>> --- a/Documentation/arch/x86/resctrl.rst
>> +++ b/Documentation/arch/x86/resctrl.rst
>> @@ -299,7 +299,13 @@ 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. Multiple
>> +    failures are not supported. A single failure encountered while
>> +    attempting to assign a task will cause the operation to abort.
>
> What happens to the already moved tasks when "abort"?
>
> Could you please add add more details on "abort"?
>
> "A single failure encountered while attempting to assign a task will 
> cause the operation to abort and already added tasks before the 
> failure will remain in the group."
Sure.
>
>> +    Failures will be logged to /sys/fs/resctrl/info/last_cmd_status.
>> +
>> +    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 725344048f85..8c91c333f9b3 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -696,11 +696,10 @@ 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)
>> -        return -EINVAL;
>>       rdtgrp = rdtgroup_kn_lock_live(of->kn);
>>       if (!rdtgrp) {
>>           rdtgroup_kn_unlock(of->kn);
>> @@ -715,7 +714,27 @@ static ssize_t rdtgroup_tasks_write(struct 
>> kernfs_open_file *of,
>>           goto unlock;
>>       }
>>   -    ret = rdtgroup_move_task(pid, rdtgrp, of);
>> +    while (buf && buf[0] != '\0' && buf[0] != '\n') {
>> +        pid_str = strim(strsep(&buf, ","));
>> +
>> +        if (kstrtoint(pid_str, 0, &pid)) {
>> +            rdt_last_cmd_puts("Task list parsing error\n");
>
> It would be better to show the failed pid string in the failure report:
> +            rdt_last_cmd_puts("Task list parsing error pid %s\n", 
> pid_str);
>
> So user will know which pid string causes the failure?

It was already discussed. Printing the characters during parsing error 
may not be much useful.

Thanks

Babu