linux-kernel - [PATCH v2 0/1] mm/gup: avoid an unnecessary allocation call for FOLL

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Message-ID: <20241105032944.141488-1-jhubbard@nvidia.com>
Date: Mon,  4 Nov 2024 19:29:43 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org,
	John Hubbard <jhubbard@...dia.com>,
	David Hildenbrand <david@...hat.com>,
	Vivek Kasireddy <vivek.kasireddy@...el.com>,
	Dave Airlie <airlied@...hat.com>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Matthew Wilcox <willy@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Jason Gunthorpe <jgg@...dia.com>,
	Peter Xu <peterx@...hat.com>,
	Arnd Bergmann <arnd@...db.de>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Dongwon Kim <dongwon.kim@...el.com>,
	Hugh Dickins <hughd@...gle.com>,
	Junxiao Chang <junxiao.chang@...el.com>,
	Mike Kravetz <mike.kravetz@...cle.com>,
	Oscar Salvador <osalvador@...e.de>,
	linux-stable@...r.kernel.org
Subject: [PATCH v2 0/1] mm/gup: avoid an unnecessary allocation call for FOLL_LONGTERM cases

This applies to today's mm-hotfixes-unstable (only). In order to test
this, my earlier patch is a prequisite: commit 255231c75dcd ("mm/gup:
stop leaking pinned pages in low memory conditions").

Changes since v1 [1]:

1) Completely different implementation: instead of changing the
allocator from kmalloc() to kvmalloc(), just avoid allocations entirely.

Note that David's original suggestion [2] included something that I've
left out for now, mostly because it's a pre-existing question and
deserves its own patch. But also, I don't understand it yet, either.


[1] https://lore.kernel.org/20241030030116.670307-1-jhubbard@nvidia.com

[2] https://lore.kernel.org/8d9dc103-47c5-4719-971a-31efb091432a@redhat.com


thanks,
John Hubbard

Cc: David Hildenbrand <david@...hat.com>
Cc: Vivek Kasireddy <vivek.kasireddy@...el.com>
Cc: Dave Airlie <airlied@...hat.com>
Cc: Gerd Hoffmann <kraxel@...hat.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Jason Gunthorpe <jgg@...dia.com>
Cc: Peter Xu <peterx@...hat.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Dongwon Kim <dongwon.kim@...el.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Junxiao Chang <junxiao.chang@...el.com>
Cc: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: linux-stable@...r.kernel.org

John Hubbard (1):
  mm/gup: avoid an unnecessary allocation call for FOLL_LONGTERM cases

 mm/gup.c | 116 ++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 77 insertions(+), 39 deletions(-)


base-commit: 0012ab094cad019afcd07bdfc28e2946537e715c
-- 
2.47.0