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From:   Kazuhito Hagio <k-hagio@ab.jp.nec.com>
To:     Lianbo Jiang <lijiang@redhat.com>
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Subject: RE: [PATCH 1/2 v4] kdump: add the vmcoreinfo documentation
Thread-Topic: [PATCH 1/2 v4] kdump: add the vmcoreinfo documentation
Thread-Index: AQHUmCarLJirG+8GGUKf+iqFxfsfO6WclVbw
Date:   Thu, 3 Jan 2019 19:28:14 +0000
Message-ID: <4AE2DC15AC0B8543882A74EA0D43DBEC035656E1@BPXM09GP.gisp.nec.co.jp>
References: <20181220054044.30738-1-lijiang@redhat.com>
 <20181220054044.30738-2-lijiang@redhat.com>
In-Reply-To: <20181220054044.30738-2-lijiang@redhat.com>
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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.

> +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.

> +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