From: Matthew Wilcox <willy@infradead.org>
To: Ackerley Tng <ackerleytng@google.com>
Cc: akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
david@redhat.com, michael.roth@amd.com, vannapurve@google.com
Subject: Re: [RFC PATCH 0/4] Extend xas_split* to support splitting arbitrarily large entries
Date: Mon, 17 Nov 2025 23:22:44 +0000 [thread overview]
Message-ID: <aRuuRGxw2vuXcVv6@casper.infradead.org> (raw)
In-Reply-To: <20251117224701.1279139-1-ackerleytng@google.com>
On Mon, Nov 17, 2025 at 02:46:57PM -0800, Ackerley Tng wrote:
> guest_memfd is planning to store huge pages in the filemap, and
> guest_memfd's use of huge pages involves splitting of huge pages into
> individual pages. Splitting of huge pages also involves splitting of
> the filemap entries for the pages being split.
Hm, I'm not most concerned about the number of nodes you're allocating.
I'm most concerned that, once we have memdescs, splitting a 1GB page
into 512 * 512 4kB pages is going to involve allocating about 20MB
of memory (80 bytes * 512 * 512). Is this necessary to do all at once?
next prev parent reply other threads:[~2025-11-17 23:22 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-17 22:46 Ackerley Tng
2025-11-17 22:46 ` [RFC PATCH 1/4] XArray: Initialize nodes while splitting instead of while allocating Ackerley Tng
2025-11-17 22:46 ` [RFC PATCH 2/4] XArray: Update xas_split_alloc() to allocate enough nodes to split large entries Ackerley Tng
2025-11-17 22:47 ` [RFC PATCH 3/4] XArray: Support splitting for arbitrarily " Ackerley Tng
2025-11-17 22:47 ` [RFC PATCH 4/4] XArray: test: Increase split order test range in check_split() Ackerley Tng
2025-11-17 23:22 ` Matthew Wilcox [this message]
2025-11-17 23:43 ` [RFC PATCH 0/4] Extend xas_split* to support splitting arbitrarily large entries Ackerley Tng
2025-11-18 8:51 ` David Hildenbrand (Red Hat)
2025-12-05 0:38 ` Ackerley Tng
2025-11-18 8:46 ` [syzbot ci] " syzbot ci
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