linux-kernel - [PATCH 0/2] frozen pages for large kmalloc

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Message-Id: <20250529-frozen-pages-for-large-kmalloc-v1-0-b3aa52a8fa17@suse.cz>
Date: Thu, 29 May 2025 10:56:25 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Christoph Lameter <cl@...ux.com>, David Rientjes <rientjes@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
 Roman Gushchin <roman.gushchin@...ux.dev>, Harry Yoo <harry.yoo@...cle.com>, 
 Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org, 
 linux-kernel@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 0/2] frozen pages for large kmalloc

In [1] I have suggested we start warning for get_page() done on large
kmalloc pages as the first step to convert them to frozen pages.
We exposed to -next and indeed got such a warning [2]. But it turns out
the code is using sendpage_ok() and thus would avoid the get_page() if
the page was actually frozen.

So in this version, freeze the large kmalloc pages at the same time as
adding the warnings and refusals to get_page/put_page() on large kmalloc
pages, the same as we do for slab pages - in patch 1.

While doing that I've noticed that large kmalloc doesn't observe numa
policies, while the rest of the allocator does. So I've done that in
patch 2 as I assume Christopher would welcome this change.

Given the timing I would expose this to -next after the current merge
window closes, thus towards 6.17.

[1] https://lore.kernel.org/all/20250417074102.4543-2-vbabka@suse.cz/
[2] https://lore.kernel.org/all/202505221248.595a9117-lkp@intel.com/

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
Vlastimil Babka (2):
      mm, slab: use frozen pages for large kmalloc
      mm, slab: support NUMA policy for large kmalloc

 include/linux/mm.h | 4 +++-
 mm/slub.c          | 9 +++++++--
 2 files changed, 10 insertions(+), 3 deletions(-)
---
base-commit: 9c32cda43eb78f78c73aee4aa344b777714e259b
change-id: 20250529-frozen-pages-for-large-kmalloc-bd4d2522e52b

Best regards,
-- 
Vlastimil Babka <vbabka@...e.cz>