linux-kernel - Re: [PATCH RESEND v2 4/6] mm/page_alloc: sort out the alloc_contig

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Message-ID: <Z1AaC5Hj2RV_5FDD@localhost.localdomain>
Date: Wed, 4 Dec 2024 09:59:55 +0100
From: Oscar Salvador <osalvador@...e.de>
To: David Hildenbrand <david@...hat.com>
Cc: Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
	Andrew Morton <akpm@...ux-foundation.org>, Zi Yan <ziy@...dia.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Naveen N Rao <naveen@...nel.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>
Subject: Re: [PATCH RESEND v2 4/6] mm/page_alloc: sort out the
 alloc_contig_range() gfp flags mess

On Tue, Dec 03, 2024 at 08:19:02PM +0100, David Hildenbrand wrote:
> It was always set using "GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL",
> and I removed the same flag combination in #2 from memory offline code, and
> we do have the exact same thing in do_migrate_range() in
> mm/memory_hotplug.c.
> 
> We should investigate if__GFP_HARDWALL is the right thing to use here, and
> if we can get rid of that by switching to GFP_KERNEL in all these places.

Why would not we want __GFP_HARDWALL set?
Without it, we could potentially migrate the page to a node which is not
part of the cpuset of the task that originally allocated it, thus violating the
policy? Is not that a problem?
 

-- 
Oscar Salvador
SUSE Labs