Hi Babu,
On 5/5/2023 10:09 AM, Moger, Babu wrote:
> [AMD Official Use Only - General]
>
> Hi Reinette,
>
>> -----Original Message-----
>> From: Reinette Chatre <reinette.chatre@xxxxxxxxx>
>> Sent: Thursday, May 4, 2023 1:58 PM
>> To: Moger, Babu <Babu.Moger@xxxxxxx>; corbet@xxxxxxx;
>> tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; bp@xxxxxxxxx
>> Cc: fenghua.yu@xxxxxxxxx; dave.hansen@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx;
>> hpa@xxxxxxxxx; paulmck@xxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx;
>> quic_neeraju@xxxxxxxxxxx; rdunlap@xxxxxxxxxxxxx;
>> damien.lemoal@xxxxxxxxxxxxxxxxxx; songmuchun@xxxxxxxxxxxxx;
>> peterz@xxxxxxxxxxxxx; jpoimboe@xxxxxxxxxx; pbonzini@xxxxxxxxxx;
>> chang.seok.bae@xxxxxxxxx; pawan.kumar.gupta@xxxxxxxxxxxxxxx;
>> jmattson@xxxxxxxxxx; daniel.sneddon@xxxxxxxxxxxxxxx; Das1, Sandipan
>> <Sandipan.Das@xxxxxxx>; tony.luck@xxxxxxxxx; james.morse@xxxxxxx;
>> linux-doc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
>> bagasdotme@xxxxxxxxx; eranian@xxxxxxxxxx; christophe.leroy@xxxxxxxxxx;
>> jarkko@xxxxxxxxxx; adrian.hunter@xxxxxxxxx; quic_jiles@xxxxxxxxxxx;
>> peternewman@xxxxxxxxxx
>> Subject: Re: [PATCH v4 1/7] x86/resctrl: Add multiple tasks to the resctrl group
>> at once
>>
>> Hi Babu,
>>
>> On 4/17/2023 4:34 PM, Babu Moger wrote:
>>> The resctrl task assignment for MONITOR or CONTROL group needs to be
>>> done one at a time. For example:
>>
>> Why all caps for monitor and control? If the intention is to use the terms for
>> these groups then it may be easier to use the same terms as in the
>> documentation, or you could just not use all caps like you do in later patches.
>
> Sure.
>>
>>>
>>> $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:
>>
>> Please use imperative mood (see Documentation/process/maintainer-tip.rst).
>>
>> Something like:
>> "Improve multiple task id assignment ...."
>
> How about:
> "Improve the assignment by supporting multiple task id assignment in
> one command with the tasks separated by commas."
The double use of 'assignment' can be confusing. This is also a
changelog where a clear context->problem->solution format can help.
If your changelog is clear regarding the context and problem then it
can end with brief solution description like:
"Support multiple task assignment in one command with tasks ids separated
by commas. For example: " (and also please use a non-x86 term for the group
name in your example)
>>> $echo 123,456,789 > /sys/fs/resctrl/clos1/tasks
>>>
...
>>> + pid will be logged in /sys/fs/resctrl/info/last_cmd_status file.
>>
>> Would it not always print the failing pid (if error was encountered while
>
> Not always. In this case it does not print the pid,
> rdt_last_cmd_puts("Can't move task to different control group\n");
> return -EINVAL;
>
What you quote above adds the relevant text to the last_cmd_status buffer ...
and later (see below) more text is added to the buffer that contains the
pid, no?
...
>>> 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';
>>> +
>>
>> This seems like another remnant of the schemata write code that expects that
>> the buffer ends with a '\n'. Since this code does not have this requirement the
>> above may have unintended consequences if a tool provides a buffer that does
>> not end with '\n'.
>> I think you just want to ensure that the buffer is properly terminated and from
>> what I understand when looking at kernfs_fop_write_iter() this is already taken
>> care of.
>
> Sure. Will check. Then I will have to change the check below to if (!buf).
Please check what kernfs_fop_write_iter() does. From what I can tell it does
exactly what you are trying to do above, but without overwriting
part of the string that user space provides.
I thus do not think that the later check needs to change. From what I understand
it is used to handle the scenario if user space provides a string like "pid,"
(last character is the separator). Please do confirm that the code can handle
any variations that user space may throw at it.
>>> @@ -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);
Note here the pid is added to the buffer that is printed when user space
views last_cmd_status. I think this is the first time two lines of error may
be added to the buffer so you could double check all works as expected.
Reinette
