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b=M8jfexNRiMmn5SqJpBK6o3SBKOT0HgRRk9cgWxXQbDn6pmXiFaiW2OMkxLHbUwS5d AWY3tunpj+e3LTLNE6nOknZGSZu/zBOT4QQRUMfbIxV40WhmGPFoIfks2bG9gJwIco iAgzaVlcT+BSLLgdxPzrtPNJcORV+bgYVOmdu5jY= Date: Sun, 27 Sep 2026 20:38:18 -0700 From: Andrew Morton To: Martin Cracauer Cc: linux-mm@kvack.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, peterx@redhat.com, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH] selftests/mm: uffd-missing-wp: add GC related functionality test Message-Id: <20260927203818.2f4b34b37f4a6e1685c3d142@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: BFAAB40002 X-Stat-Signature: kj89u6n8qs56kt6hfyheuhcntsjewwzb X-HE-Tag: 1790566700-121054 X-HE-Meta: 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 c7AcQtxe fOsqQtyfagMEc9A1O0GeeJNb4fmWoCCa/EUXQijCAPJEgLaiLmjRp+VfNofKYhi83Tc0u1H4iMwTUYmqd5GGEwc2OH88TMH9aFaVIf2kRsikE5qCWtNa3PALBTwF7rQASZRc4/Ij1g/DNGcjD4T2/z/FOSSGXpGQ0VXB4dse61UVSxx+T6QEoK/UrEIPs0kYmE7RWlARuLpAiAf5c36TK6wd/Tmh7d2O0PfnNVTFl3aRgDlAMi1n4BBK6YcOZpJKSa5J6e/pyyux6xYjmc2nUjn2jasx+OQgRa7lGcap7EHdb4lGzf4z8tjwCUEMNTpqup8bt4I9wUf+4peGb4i5EmcipDcXZfHgnfjrVzG9D126phEn1gbohD5aMFF39EdQ9yWvhW1vIEtlcJGE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, 27 Sep 2026 23:26:31 -0400 Martin Cracauer wrote: > Add a test that asserts that functionality needed for generational > garbage collection works. Namely to implement a write barrier using > userfaultfd instead of using segmentation faults. The planned target > is the GC in SBCL. > > The real GC will initially fill heap pages by using on-demand loading > of pages from an image file, either via mmap(2) or using userfaultfd > to decompress a page read from an image file made from individually > compressed blocks. This test doesn't do that so that it needs no disk > I/O and no decompression library. Instead, a fault will be filled by > copying page content from prepared pages in the heap. Thanks. Sashiko asked a couple of things: https://sashiko.dev/#/patchset/arneZ-KkRWUNI0Ho@cons.org