linux-kernel - Re: [PATCHv2 3/8] mm: Accept memory in __alloc_pages

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Message-ID: <5aqorjb62kozvqehdw5ei6ov4gol6kcu72mteqso7v72jvnrgn@gdgpyjhhz65q>
Date: Mon, 12 Aug 2024 09:24:53 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	"Borislav Petkov (AMD)" <bp@...en8.de>, Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>, 
	Mike Rapoport <rppt@...nel.org>, "Matthew Wilcox (Oracle)" <willy@...radead.org>, 
	David Hildenbrand <david@...hat.com>, Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 3/8] mm: Accept memory in __alloc_pages_bulk().

On Fri, Aug 09, 2024 at 10:31:03AM -0500, Tom Lendacky wrote:
> On 8/9/24 06:48, Kirill A. Shutemov wrote:
> > Currently, the kernel only accepts memory in get_page_from_freelist(),
> > but there is another path that directly takes pages from free lists -
> > __alloc_page_bulk(). This function can consume all accepted memory and
> > will resort to __alloc_pages_noprof() if necessary.
> > 
> > Conditionally accepted in __alloc_pages_bulk().
> > 
> > The same issue may arise due to deferred page initialization. Kick the
> > deferred initialization machinery before abandoning the zone, as the
> > kernel does in get_page_from_freelist().
> 
> Is the deferred page init issue an existing problem? In other words,
> should it be a separate patch with a Fixes: tag so it can go back to
> stable kernels?

Yes, it is existing problem, but the problem is transient (deferred thread
will add more pages) and there's fallback to __alloc_pages_noprof() which
knowns how to handle deferred pages. I don't think it is worth
backporting.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov