linux-kernel - Re: [PATCH v2 3/3] vsprintf: dump full information of page flags in pGp

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Date:   Mon, 1 Feb 2021 14:23:33 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Yafang Shao <laoar.shao@...il.com>,
        andriy.shevchenko@...ux.intel.com, vbabka@...e.cz,
        linmiaohe@...wei.com, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, pmladek@...e.com, rostedt@...dmis.org,
        sergey.senozhatsky@...il.com, linux@...musvillemoes.dk
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Joe Perches <joe@...ches.com>
Subject: Re: [PATCH v2 3/3] vsprintf: dump full information of page flags in
 pGp

On 01.02.21 12:56, Yafang Shao wrote:
> Currently the pGp only shows the names of page flags, rather than
> the full information including section, node, zone, last cpupid and
> kasan tag. While it is not easy to parse these information manually
> because there're so many flavors. Let's interpret them in pGp as well.
> 
> - Before the patch,
> [ 6343.396602] Slab 0x000000004382e02b objects=33 used=3 fp=0x000000009ae06ffc flags=0x17ffffc0010200(slab|head)
> 
> - After the patch,
> [ 6871.296131] Slab 0x00000000c0e19a37 objects=33 used=3 fp=0x00000000c4902159 flags=0x17ffffc0010200(Node 0,Zone 2,Lastcpupid 0x1fffff,slab|head)

For debugging purposes, it might be helpful to have the actual zone name 
(and to know if the value is sane). You could obtain it (without other 
modifications) via

const char zname = "Invalid";

if (zone < MAX_NR_ZONES)
	zname = first_online_pgdat()->node_zones[zone].name;


Similarly, it might also be helpful to indicate if a node is 
online/offline/invalid/.

const char nstate = "Invalid";

if (node_online(nid))
	nstate = "Online";
else if (node_possible(nid))
	nstate = "Offline";


Printing that in addition to the raw value could be helpful. Just some 
thoughts.

-- 
Thanks,

David / dhildenb