linux-kernel - Re: [PATCH v4] tools/mm: Add script to display page state for a given PID and VADDR

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Message-ID: <7867c19d-bd6c-4f8a-a227-1145fa0516d9@linux.dev>
Date: Fri, 30 May 2025 11:18:59 +0800
From: Ye Liu <ye.liu@...ux.dev>
To: SeongJae Park <sj@...nel.org>
Cc: akpm@...ux-foundation.org, linux-debuggers@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 linux-toolchains@...r.kernel.org, osandov@...ndov.com, paulmck@...nel.org,
 sweettea-kernel@...miny.me, liuye@...inos.cn, fweimer@...hat.com
Subject: Re: [PATCH v4] tools/mm: Add script to display page state for a given
 PID and VADDR


在 2025/5/29 07:42, SeongJae Park 写道:
> On Wed, 28 May 2025 17:15:43 +0800 Ye Liu <ye.liu@...ux.dev> wrote:
>
>> From: Ye Liu <liuye@...inos.cn>
>>
>> Introduces a new drgn script, `show_page_info.py`, which allows users
>> to analyze the state of a page given a process ID (PID) and a virtual
>> address (VADDR). This can help kernel developers or debuggers easily
>> inspect page-related information in a live kernel or vmcore.
>>
>> The script extracts information such as the page flags, mapping, and
>> other metadata relevant to diagnosing memory issues.
>>
>> Output example:
>> sudo ./show_page_info.py 1 0x7fb3eb1b2000
>> PID: 1 Comm: systemd mm: 0xffff8d27279f9cc0
>> Raw: 0017ffffc000416c fffff31105a61b08 fffff31105a63608 ffff8d27121326a8
>> Raw: 0000000000000000 ffff8d271b9dcc40 0000002500000007 ffff8d2711f12700
>> User Virtual Address: 0x7fb3eb1b2000
> This is same to what the user passes as the input.  I think this is not really
> needed?

It will be removed in the next version.

>> Page Address:         0xfffff31106356a00
>> Page Flags:           PG_referenced|PG_uptodate|PG_lru|PG_head|PG_active|
>>                       PG_private|PG_reported|PG_has_hwpoisoned
>> Page Size:            4096
>> Page PFN:             0x18d5a8
>> Page Physical:        0x18d5a8000
>> Page Virtual:         0xffff8d274d5a8000
>> Page Refcount:        37
>> Page Mapcount:        7
>> Page Index:           0x0
>> Page Memcg Data:      0xffff8d2711f12700
>> Memcg Name:           init.scope
>> Memcg Path:           /sys/fs/cgroup/memory/init.scope
> On my setup, above two lines look like below:
>
>     Memcg Name:           unknown
>     Memcg Path:           Unexpected error: 'struct kernfs_node' has no member 'parent'
>
> Maybe there are rooms to improve?
The drgn version needs to be updated.
>> Page Mapping:         0xffff8d27121326a8
>> Page Anon/File:       File
>> Page VMA:             0xffff8d26cac47600
>> VMA Start:            0x7fb3eb1b2000
>> VMA End:              0x7fb3eb1b6000
>> This page is part of a compound page.
>> This page is the head page of a compound page.
>> Head Page:            0xfffff31106356a00
>> Compound Order:       2
>> Number of Pages:      4
>>
>> Signed-off-by: Ye Liu <liuye@...inos.cn>
> On my setup, this tool works without obvious or significant errors.
>
> Tested-by: SeongJae Park <sj@...nel.org>
>
Thanks,
Ye

> Thanks,
> SJ
>
> [...]