linux-kernel - Re: [PATCH] mm/code_tag: Skip displaying the code

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Message-ID: <2c97de38-4256-47c4-97e4-7d1cb6c30fc0@quicinc.com>
Date: Fri, 13 Dec 2024 11:51:01 +0800
From: Zhenhua Huang <quic_zhenhuah@...cinc.com>
To: Suren Baghdasaryan <surenb@...gle.com>
CC: <akpm@...ux-foundation.org>, <kent.overstreet@...ux.dev>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH] mm/code_tag: Skip displaying the code_tag if it is not
 called



On 2024/12/13 10:44, Suren Baghdasaryan wrote:
> On Wed, Dec 11, 2024 at 11:50 PM Zhenhua Huang
> <quic_zhenhuah@...cinc.com> wrote:
>>
>> Hi Suren,
>>
>> On 2024/12/12 15:16, Suren Baghdasaryan wrote:
>>> On Wed, Dec 11, 2024 at 12:56 AM Zhenhua Huang
>>> <quic_zhenhuah@...cinc.com> wrote:
>>>>
>>>> /proc/allocinfo is full of callsites which are not called at all.
>>>> Let's only output if the callsite actually been invoked.
>>>
>>> No, I disagree. Allocation that was never invoked is not the same as
>>> no allocation at all. How would we know the difference if we filter
>>
>> But it doesn't affect further display when it is actually called? why we
>> need to know the diff here...
>>
>> The point from me is: up to now, the callsite hasn't been invoked, so it
>> can be ignored in the output.. The original output is really huge..
> 
> My point is that with this change we lose information which can be
> useful. For example if I want to analyze all the places in the kernel
> where memory can be potentially allocated, your change would prevent
> me from doing that.

OK, Thanks, got it.

> 
>>
>>> out the empty ones?
>>> If you don't want to see all the unused sites, you can filter them in
>>> the userspace. I also suspect that for practical purposes you would
>>> want to filter small ones (below some threshold) as well.
>>
>> Yeah, that's the expected way from us as well :)
>>
>>>
>>>>
>>>> Signed-off-by: Zhenhua Huang <quic_zhenhuah@...cinc.com>
>>>> ---
>>>>    lib/alloc_tag.c | 10 ++++++----
>>>>    1 file changed, 6 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
>>>> index 35f7560a309a..06fb7eb5c0bc 100644
>>>> --- a/lib/alloc_tag.c
>>>> +++ b/lib/alloc_tag.c
>>>> @@ -95,10 +95,12 @@ static void alloc_tag_to_text(struct seq_buf *out, struct codetag *ct)
>>>>           struct alloc_tag_counters counter = alloc_tag_read(tag);
>>>>           s64 bytes = counter.bytes;
>>>>
>>>> -       seq_buf_printf(out, "%12lli %8llu ", bytes, counter.calls);
>>>> -       codetag_to_text(out, ct);
>>>> -       seq_buf_putc(out, ' ');
>>>> -       seq_buf_putc(out, '\n');
>>>> +       if (bytes || counter.calls) {
>>>> +               seq_buf_printf(out, "%12lli %8llu ", bytes, counter.calls);
>>>> +               codetag_to_text(out, ct);
>>>> +               seq_buf_putc(out, ' ');
>>>> +               seq_buf_putc(out, '\n');
>>>> +       }
>>>>    }
>>>>
>>>>    static int allocinfo_show(struct seq_file *m, void *arg)
>>>> --
>>>> 2.25.1
>>>>
>>