linux-kernel - Re: [PATCH] slub: fix slub segmentation

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Date: Fri, 5 Apr 2024 11:05:26 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: "Christoph Lameter (Ampere)" <cl@...ux.com>,
 Ming Yang <yangming73@...wei.com>
Cc: penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
 akpm@...ux-foundation.org, roman.gushchin@...ux.dev, 42.hyeyoo@...il.com,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, zhangliang5@...wei.com,
 wangzhigang17@...wei.com, liushixin2@...wei.com, alex.chen@...wei.com,
 pengyi.pengyi@...wei.com, xiqi2@...wei.com
Subject: Re: [PATCH] slub: fix slub segmentation

On 4/4/24 9:12 PM, Christoph Lameter (Ampere) wrote:
> On Tue, 2 Apr 2024, Ming Yang wrote:
> 
>> The key point of above allocation flow is: the slab should be alloced
>> from the partial of other node first, instead of the buddy system of
>> other node directly.
> 
> 
> If you use GFP_THISNODE then you will trigger a reclaim pass on the remote 
> node. That could generate a performance regression.

Note the alternative approach I merged doesn't have this issue because it
uses GFP_NOWAIT for that __GFP_THISNODE attempt.

https://lore.kernel.org/all/20240330082335.29710-1-chenjun102@huawei.com/


> We already support this kind of behavior via the node_reclaim / 
> zone_reclaiom setting in procfs. Please use that.
> 
> The remote buildup of the partial pages can be addressed by changing the 
> remote_node_defrag_ratio in the slabs. This will make slub scan remote 
> nodes for partial slabs before going into the page allocator.
> 
>