linux-kernel - Re: [PATCH] mm/slab: Add slabreclaim flag to slabinfo

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Message-ID: <58191e1b-7ebc-16ff-1df0-16ddcaa2e7b9@linux.com>
Date: Mon, 5 Feb 2024 09:54:34 -0800 (PST)
From: "Christoph Lameter (Ampere)" <cl@...ux.com>
To: Vlastimil Babka <vbabka@...e.cz>
cc: Greg KH <gregkh@...uxfoundation.org>, 
    Fangzheng Zhang <fangzheng.zhang@...soc.com>, 
    Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, 
    Joonsoo Kim <iamjoonsoo.kim@....com>, 
    Andrew Morton <akpm@...ux-foundation.org>, 
    Roman Gushchin <roman.gushchin@...ux.dev>, 
    Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org, 
    linux-kernel@...r.kernel.org, 
    Fangzheng Zhang <fangzheng.zhang1003@...il.com>, 
    Yuming Han <yuming.han@...soc.com>, Chunyan Zhang <zhang.lyra@...il.com>
Subject: Re: [PATCH] mm/slab: Add slabreclaim flag to slabinfo

On Mon, 5 Feb 2024, Vlastimil Babka wrote:

> On 2/4/24 14:09, Greg KH wrote:
>> On Wed, Jan 31, 2024 at 05:44:42PM +0800, Fangzheng Zhang wrote:
>>> In order to enhance slab debugging, we add slabreclaim flag to
>>> slabinfo. Slab type is also an important analysis point in slabinfo
>>> for per slab, when various problems such as memory leaks or memory
>>> statistics occur.
>>>
>>> Signed-off-by: Fangzheng Zhang <fangzheng.zhang@...soc.com>
>>> ---
>>>  mm/slab_common.c | 7 ++++---
>>>  1 file changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/mm/slab_common.c b/mm/slab_common.c
>>> index 238293b1dbe1..aeeb2bfe6dda 100644
>>> --- a/mm/slab_common.c
>>> +++ b/mm/slab_common.c
>>> @@ -1038,7 +1038,7 @@ static void print_slabinfo_header(struct seq_file *m)
>>>  	seq_puts(m, "slabinfo - version: 2.1\n");
>>>  	seq_puts(m, "# name            <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab>");
>>>  	seq_puts(m, " : tunables <limit> <batchcount> <sharedfactor>");
>>> -	seq_puts(m, " : slabdata <active_slabs> <num_slabs> <sharedavail>");
>>> +	seq_puts(m, " : slabdata <active_slabs> <num_slabs> <sharedavail> <slabreclaim>");
>>
>> Doesn't this change the slabinfo version number above?  Where is this
>> change documented so that userspace knows about it?

I have never seen such a document. I would suggest incrementing the 
version to 2.2 since there is a minor extension of the format.

I tried to remove /proc/slabinfo in the past and have people use the more 
versatile /sys/kernel/slab interface. But /proc/slabinfo has a long 
legacy.

Could we mark /proc/slabinfo as deprecated and recommend the use of
either sysfs directly or use of the "slabinfo" tool that we have 
been providing in linux/tools/mm for a long time?