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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aO5o548uQAuBcw0P@tiehlicka>
Date: Tue, 14 Oct 2025 17:14:47 +0200
From: Michal Hocko <mhocko@...e.com>
To: Shakeel Butt <shakeel.butt@...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>,
	Roman Gushchin <roman.gushchin@...ux.dev>
Subject: Re: [RFC PATCH] mm: net: disable kswapd for high-order network
 buffer allocation

On Tue 14-10-25 07:27:06, Shakeel Butt wrote:
> On Tue, Oct 14, 2025 at 09:26:49AM +0200, Michal Hocko wrote:
> > On Mon 13-10-25 20:30:13, Vlastimil Babka wrote:
> > > On 10/13/25 12:16, Barry Song wrote:
> > > > From: Barry Song <v-songbaohua@...o.com>
> > [...]
> > > I wonder if we should either:
> > > 
> > > 1) sacrifice a new __GFP flag specifically for "!allow_spin" case to
> > > determine it precisely.
> > 
> > As said in other reply I do not think this is a good fit for this
> > specific case as it is all or nothing approach. Soon enough we discover
> > that "no effort to reclaim/compact" hurts other usecases. So I do not
> > think we need a dedicated flag for this specific case. We need a way to
> > tell kswapd/kcompactd how much to try instead.
> 
> To me this new floag is to decouple two orthogonal requests i.e. no lock
> semantic and don't wakeup kswapd. At the moment the lack of kswapd gfp
> flag convey the semantics of no lock. This can lead to unintended usage
> of no lock semantics by users which for whatever reason don't want to
> wakeup kswapd.

I would argue that callers should have no business into saying whether
the MM should wake up kswapd or not. The flag name currently suggests
that but that is mostly for historic reasons. A random page allocator
user shouldn't really care about this low level detail, really.
-- 
Michal Hocko
SUSE Labs