linux-kernel - Re: [RFC PATCH] mm: net: disable kswapd for high-order network buffer allocation

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Message-ID: <aO36oKRR3UliRFR5@tiehlicka>
Date: Tue, 14 Oct 2025 09:24:16 +0200
From: Michal Hocko <mhocko@...e.com>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Vlastimil Babka <vbabka@...e.cz>, Barry Song <21cnbao@...il.com>,
	netdev@...r.kernel.org, linux-mm@...ck.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Barry Song <v-songbaohua@...o.com>,
	Jonathan Corbet <corbet@....net>,
	Eric Dumazet <edumazet@...gle.com>,
	Kuniyuki Iwashima <kuniyu@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Willem de Bruijn <willemb@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Simon Horman <horms@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Brendan Jackman <jackmanb@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>, Zi Yan <ziy@...dia.com>,
	Yunsheng Lin <linyunsheng@...wei.com>,
	Huacai Zhou <zhouhuacai@...o.com>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Harry Yoo <harry.yoo@...cle.com>,
	David Hildenbrand <david@...hat.com>,
	Matthew Wilcox <willy@...radead.org>
Subject: Re: [RFC PATCH] mm: net: disable kswapd for high-order network
 buffer allocation

On Mon 13-10-25 15:46:54, Roman Gushchin wrote:
> Vlastimil Babka <vbabka@...e.cz> writes:
> 
> > On 10/13/25 12:16, Barry Song wrote:
[...]
> >> An alternative approach is to disable kswapd for these frequent
> >> allocations and provide best-effort order-3 service for both TX and RX paths,
> >> while removing the sysctl entirely.
> 
> I'm not sure this is the right path long-term. There are significant
> benefits associated with using larger pages, so making the kernel fall
> back to order-0 pages easier and sooner feels wrong, tbh. Without kswapd
> trying to defragment memory, the only other option is to force tasks
> into the direct compaction and it's known to be problematic.
> 
> I wonder if instead we should look into optimizing kswapd to be less
> power-hungry?

Exactly. If your specific needs prefer low power consumption to higher
order pages availability then we should have more flixible way to say
that than a hardcoded allocation mode. We should be able to tell
kswapd/kcompactd how much to try for those allocations.
-- 
Michal Hocko
SUSE Labs