linux-kernel - Re: [PATCH 1/2 v4] kdump: add the vmcoreinfo documentation

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Date:   Fri, 4 Jan 2019 10:28:20 +0800
From:   lijiang <lijiang@...hat.com>
To:     Kazuhito Hagio <k-hagio@...jp.nec.com>
Cc:     "bhe@...hat.com" <bhe@...hat.com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "dyoung@...hat.com" <dyoung@...hat.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2 v4] kdump: add the vmcoreinfo documentation

在 2019年01月04日 03:28, Kazuhito Hagio 写道:
> Hi Lianbo,
> 
> -----Original Message-----
>> +=======================
>> +What is the VMCOREINFO?
>> +=======================
>> +
>> +VMCOREINFO is a special ELF note section. It contains various
>> +information from the kernel like structure size, page size, symbol
>> +values, field offsets, etc. These data are packed into an ELF note
>> +section and used by user-space tools like crash and makedumpfile to
>> +analyze a kernel's memory layout.
>> +
>> +To dump the VMCOREINFO contents, one can do:
>> +
>> +# makedumpfile -g VMCOREINFO -x vmlinux
> 
> again, this command does not dump the VMCOREINFO in ELF note section.
> It converts the vmlinux's debug infomation into a VMCOREINFO-like data.
> So I don't think this command is suitable to introduce here.
> 

Thank you, Kazu.

As you mentioned, makedumpfile in 'devel' branch can print VMCOREINFO in /proc/kcore,
can i add the following command to this document?

#makedumpfile --mem-usage /proc/kcore -D

>> +PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|
>> +PG_hwpoision|PG_head_mask
>> +-----------------------------------------------------
>> +
>> +Page attributes. These flags are used to filter free pages.
> 
> Some of these are not used to filter *free* pages, so
> 
> ... used to filter various unnecessary pages.
> 

Great. I will modify it in next post.

And also merge the 'PG_buddy' and 'PG_offline'  into the PG_* flag here.

Many thanks.

Lianbo

>> +PAGE_BUDDY_MAPCOUNT_VALUE or ~PG_buddy
>> +--------------------------------------
> 
> then, this can be merged into the one above?
> 
>> +======
>> +x86_64
>> +======
> ...
>> +PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)
>> +----------------------------------------
> 
> This looks not only for x86_64, and also can be merged into
> the PG_* flags?
> 
> Thank you for your effort!
> Kazu
> 
>