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

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Date: Thu, 4 Apr 2024 12:12:11 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...ux.com>
To: Ming Yang <yangming73@...wei.com>
cc: penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com, 
    akpm@...ux-foundation.org, vbabka@...e.cz, 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 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.

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.