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

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Message-ID: <dd8d6beb-a24d-afe8-929f-acdfef544a39@amd.com>
Date:   Thu, 7 Sep 2023 09:44:41 -0500
From:   "Moger, Babu" <bmoger@....com>
To:     Fenghua Yu <fenghua.yu@...el.com>, 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 9/6/2023 3:42 PM, Fenghua Yu wrote:
> Hi, Babu,
>
> On 9/6/23 07:56, Moger, Babu wrote:
>>>> @@ -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.
>
> Could you please let me know where printing "pid_str" is discussed?

My bad.  Should have read your comments more carefully.


>
> My understanding is a similar thing is discussed in v3:
> https://lore.kernel.org/all/167778866506.1053859.2329229096484796501.stgit@bmoger-ubuntu/ 
>
>
> Then v4 has this code without printing pid_str. In v4, there is a 
> similar discussion of printing pid, but not pid_str.
>
> But I cannot find a discussion of why "pid_str" is not printed.
>
> If kstritoint(pid_str, 0, &pid) fails, without printing pid_str, how 
> can user know which pid string fails? e.g. user tries to move 100 pids 
> and the 51st pid parsing fails. It's hard for user to know the 51st 
> pid fails without showing pid_str in the error info and then it's hard 
> for the user to decide to re-do moving or aborting moving etc.

That is correct.  Will add following print statement o print the pid_str.

rdt_last_cmd_printf("Task list parsing error pid %s\n", pid_str);

Thanks

Babu