Re: [RFC PATCH v1] tools/mm: Add thpmaps script to dump THP usage info

[William Kucharski <william.kucharski@oracle.com>]

Personally I like either of these:

00000206: 0000aaaadbb20000-0000aaaadbb21000 r-xp 00000000 fe:00 00426969
     206: 0000aaaadbb20000-0000aaaadbb21000 r-xp 00000000 fe:00 00426969

With a header that looks something like this; I suspect the formatting will get
mangled in email anyway:

   PID         START             END        PROT   OFF    MJ:MN  INODE      FILE
00000206: 0000aaaadbb20000-0000aaaadbb21000 r-xp 00000000 fe:00 00426969

    -- William Kucharski

> On Jan 5, 2024, at 01:35, Ryan Roberts <ryan.roberts@arm.com> wrote:
> 
> On 04/01/2024 22:48, John Hubbard wrote:
>> On 1/3/24 02:20, Ryan Roberts wrote:
>>> On 03/01/2024 10:09, William Kucharski wrote:
>> ...
>>>>> The reason is that it is also possible to invoke the tool with --cgroup instead
>>>>> of --pid. In this case, the tool will iterate over all the pids in the
>>>>> cgroup so
>>>>> (when --summary is not specified) having the pid associated with each vma is
>>>>> useful.
>>>>> 
>>>>> I could change it to conditionally output the pid only when --cgroup is
>>>>> specified?
>>>> 
>>>> You could, or perhaps emit a colon after the pid to delineate it, e.g.:
>>>> 
>>>>> 000000ce: 0000aaaadbb20000-0000aaaadbb21000 r-xp 00000000 fe:0000426969
>>>>> /root/a.out
>>> 
>>> Yeah that sounds like the least worst option. Let's go with that.
>> 
>> I'm trying this out and had the exact same issue with pid. I'd suggest:
>> 
>> a) pid should always be printed in decimal, because that's what ps(1) uses
>>    and no one expects to see it in other formats such as hex.
> 
> right aligned with 0 or ' ' as the pad? I guess ' ' if you want it to look like
> ps? But given pid is the first column, I think it will look weird right aligned.
> Perhaps left aligned, followed by colon, followed by pad? Here are the 3 options:
> 
> 00000206: 0000aaaadbb20000-0000aaaadbb21000 r-xp 00000000 fe:00 00426969
>     206: 0000aaaadbb20000-0000aaaadbb21000 r-xp 00000000 fe:00 00426969
> 206:      0000aaaadbb20000-0000aaaadbb21000 r-xp 00000000 fe:00 00426969
> 
> My personal preference is the first option; right aligned with 0 pad.
> 
>> 
>> b) In fact, perhaps a header row would help. There could be a --no-header-row
>>    option for cases that want to feed this to other scripts, but the default
>>    would be to include a human-friendly header.
> 
> How about this for a header (with example first data row):
> 
>     PID             START              END PROT      OFF MJ:MN    INODE FILE
> 00000206: 0000aaaadbb20000-0000aaaadbb21000 r-xp 00000000 fe:00 00426969
> 
> Personally I wouldn't bother with a --no-header option; just keep it always on.
> 
>> 
>> c) pid should probably be suppressed if --pid is specified, but that's
>>    less important than the other points.
> 
> If we have the header then I think its clear what it is and I'd prefer to keep
> the data format consistent between --pid and --cgroup. So prefer to leave pid in
> always.
> 
>> 
>> In a day or two I'll get a chance to run this on something that allocates
>> lots of mTHPs, and give a closer look.
> 
> Thanks - it would be great to get some feedback on the usefulness of the actual
> counters! :)
> 
> I'm considering adding an --ignore-folio-boundaries option, which would modify
> the way the cont counters work, to only look for contiguity and alignment and
> ignore any folio boundaries. At the moment, if you have multiple contiguous
> folios, they don't count, because the memory doesn't all belong to the same
> folio. I think this could be useful in some (limited) circumstances.
> 
>> 
>> 
>> thanks,