linux-kernel - Re: [PATCH v2] mm/vmstat: Add order's information for extfrag_index and unusable

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Message-Id: <F38EE8B9-3C29-43DC-A471-3DF6242B9804@163.com>
Date: Fri, 1 Mar 2024 07:13:51 +0800
From: Hao Ge <gehao618@....com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Hao Ge <gehao@...inos.cn>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/vmstat: Add order's information for extfrag_index and unusable_index


> On Mar 1, 2024, at 02:40, Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> On Thu, 29 Feb 2024 22:14:43 +0800 Hao Ge <gehao@...inos.cn> wrote:
> 
>> Current cat /sys/kernel/debug/extfrag/extfrag_index and
>> /sys/kernel/debug/extfrag/unusable_index is not friendly to userspace.
>> 
>> We should add order's information so that users can clearly understand
>> the situation of each order at a glance like pagetypeinfo.
>> 
>> before:
>> cat /sys/kernel/debug/extfrag/extfrag_index:
>> Node 0, zone    DMA32  ...... ...... ...... ......
>> Node 0, zone   Normal  ...... ...... ...... ......
>> 
>> cat /sys/kernel/debug/extfrag/unusable_index:
>> Node 0, zone    DMA32 ..... ..... ..... .....
>> Node 0, zone   Normal ..... ..... ..... .....
>> 
>> after:
>> cat /sys/kernel/debug/extfrag/extfrag_index:
>> Extfrag index at order:       0      1      2      3
>> Node 0, zone        DMA  ...... ...... ...... ......
>> Node 0, zone     Normal  ...... ...... ...... ......
>> 
>> cat /sys/kernel/debug/extfrag/unusable_index:
>> Unusable index at order:     0     1     2     3
>> Node 0, zone         DMA ..... ..... ..... .....
>> Node 0, zone      Normal ..... ..... ..... .....
>> 
> 
> This may break existing parsers of this file.
> 
> And that would be allowed if these files were under debugfs.  But
> they're under sysfs/debug, where the rules are less clear.
> 
> Still, it's unclear to me that the benefit is worth this risk.  What do
> others think?

Thank you for your reply. This is something I didn't expect. I think it's better to keep it in its original condition to avoid compatibility issues with some tools.