linux-kernel - Re: [PATCH] mm/page_alloc: Fix memory accept before watermarks gets initialized

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Message-ID: <asxbkez3pwoc2p4jb5ftwbvapzvoj3kma2tunprrnp4ptihebb@dxhvj3uicw6c>
Date: Mon, 10 Mar 2025 14:06:20 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Mike Rapoport <rppt@...nel.org>, David Hildenbrand <david@...hat.com>, 
	Mel Gorman <mgorman@...hsingularity.net>, Tom Lendacky <thomas.lendacky@....com>, 
	"Kalra, Ashish" <ashish.kalra@....com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, linux-mm@...ck.org, 
	linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	Farrah Chen <farrah.chen@...el.com>
Subject: Re: [PATCH] mm/page_alloc: Fix memory accept before watermarks gets
 initialized

On Mon, Mar 10, 2025 at 12:37:25PM +0100, Vlastimil Babka wrote:
> On 3/10/25 09:28, Kirill A. Shutemov wrote:
> > Watermarks are initialized during the postcore initcall. Until then, all
> > watermarks are set to zero. This causes cond_accept_memory() to
> > incorrectly skip memory acceptance because a watermark of 0 is always
> > met.
> 
> What are the user-visible consequences of that?

Premature OOM on boot.

It can be triggered with certain combinations of number of vCPUs and
memory size.

> > To ensure progress, accept one MAX_ORDER page if the watermark is zero.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > Reported-and-tested-by: Farrah Chen <farrah.chen@...el.com>
> 
> Fixes:, Cc: stable etc?

Fixes: dcdfdd40fa82 ("mm: Add support for unaccepted memory")
Cc: stable@@vger.kernel.org # v6.5+

-- 
  Kiryl Shutsemau / Kirill A. Shutemov