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

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Message-ID: <yisxjdnn73ebybkdl4tisji3d7ozmsm4se2whenidjwbn2z5kl@tvigrv54qp7z>
Date: Wed, 15 Oct 2025 11:13:43 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Barry Song <21cnbao@...il.com>
Cc: Eric Dumazet <edumazet@...gle.com>, 
	Matthew Wilcox <willy@...radead.org>, 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>, 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>, Vlastimil Babka <vbabka@...e.cz>, 
	Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.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>
Subject: Re: [RFC PATCH] mm: net: disable kswapd for high-order network
 buffer allocation

On Wed, Oct 15, 2025 at 04:28:17AM +0800, Barry Song wrote:
> On Tue, Oct 14, 2025 at 10:38 PM Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> 
> > >
> > > It might be worth exploring these settings further, but I can’t quite see
> > > their connection to high-order allocations,
> >
> > I don't think there is a connection between them. Is there a reason you
> > are expecting a connection/relation between them?
> 
> Eric replied to my email about frequent high-order allocation requests,
> suggesting that I might be missing some proper configurations for these
> settings[1]. So I’m trying to understand whether these configurations affect
> the frequency of high-order allocations.

If I understand Eric correctly, those configurations do indirectly
affect the number of memory allocations and their lifetime (irrespective
of order). In one scenario, setting tcp_wmem[0] higher, allow the kernel
to allocate more memory even when the system is under memory pressure.
See tcp_wmem_schedule(). In your case it would be up to 0.5MiB per
socket.

Have you tested the configuration values suggested by Eric?