From: Matthew Wilcox <willy@infradead.org>
To: Zi Yan <ziy@nvidia.com>
Cc: "David Hildenbrand (Arm)" <david@kernel.org>,
Song Liu <songliubraving@fb.com>, Chris Mason <clm@fb.com>,
David Sterba <dsterba@suse.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Lorenzo Stoakes <ljs@kernel.org>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Nico Pache <npache@redhat.com>,
Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
Barry Song <baohua@kernel.org>, Lance Yang <lance.yang@linux.dev>,
Vlastimil Babka <vbabka@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>, Shuah Khan <shuah@kernel.org>,
linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kselftest@vger.kernel.org
Subject: Re: [RFC PATCH 02/11] mm/khugepaged: remove READ_ONLY_THP_FOR_FS code in collapse_file()
Date: Mon, 23 Mar 2026 21:02:37 +0000 [thread overview]
Message-ID: <acGqbeSjktT4biku@casper.infradead.org> (raw)
In-Reply-To: <FDC4C393-FB38-4422-9217-DAE95131C696@nvidia.com>
On Mon, Mar 23, 2026 at 04:24:26PM -0400, Zi Yan wrote:
> On 23 Mar 2026, at 16:13, David Hildenbrand (Arm) wrote:
> > I assume so, because for executables you would have to be lucky to get a
> > PMD THP? So I don't see the non-khugepaged large folio support on par
> > with khugepaged support.
Not necessarily that lucky; if you set VM_HUGEPAGE,
do_sync_mmap_readahead() will allocate PMD-sized folios automatically.
On busy database servers (and is there any other kind?), khugepaged
takes too long to run and find opportunities to collapse text pages.
Like, days.
> It is more like turning on READ_ONLY_THP_FOR_FS by default for
> FS with large folio support instead of removing it.
>
> OK, I will give it another try.
I think the test needs to be:
if (mapping_max_folio_order(mapping) >= PMD_ORDER)
as there can be cases of filesystems which support up to, say, 64KiB,
but not all the way up to 2MiB. I disapprove of this situation, but
this is where we are right now.
next prev parent reply other threads:[~2026-03-23 21:02 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-23 19:06 [RFC PATCH 00/11] Remove READ_ONLY_THP_FOR_FS Zi Yan
2026-03-23 19:06 ` [RFC PATCH 01/11] mm: remove READ_ONLY_THP_FOR_FS Kconfig option Zi Yan
2026-03-23 19:06 ` [RFC PATCH 02/11] mm/khugepaged: remove READ_ONLY_THP_FOR_FS code in collapse_file() Zi Yan
2026-03-23 19:41 ` David Hildenbrand (Arm)
2026-03-23 19:47 ` Zi Yan
2026-03-23 19:53 ` David Hildenbrand (Arm)
2026-03-23 19:59 ` Zi Yan
2026-03-23 20:13 ` David Hildenbrand (Arm)
2026-03-23 20:24 ` Zi Yan
2026-03-23 21:02 ` Matthew Wilcox [this message]
2026-03-23 21:05 ` David Hildenbrand (Arm)
2026-03-23 21:11 ` Zi Yan
2026-03-23 21:21 ` David Hildenbrand (Arm)
2026-03-24 0:12 ` Zi Yan
2026-03-24 13:15 ` Baolin Wang
2026-03-23 19:06 ` [RFC PATCH 03/11] mm: remove filemap_nr_thps*() functions Zi Yan
2026-03-23 19:06 ` [RFC PATCH 04/11] mm/huge_memory: remove file_thp_enabled() and its caller Zi Yan
2026-03-23 19:06 ` [RFC PATCH 05/11] mm/huge_memory: remove folio split check for READ_ONLY_THP_FOR_FS Zi Yan
2026-03-23 19:06 ` [RFC PATCH 06/11] mm/truncate: use folio_split() in truncate_inode_partial_folio() Zi Yan
2026-03-23 19:06 ` [RFC PATCH 07/11] fs: remove nr_thp from struct address_space Zi Yan
2026-03-23 19:06 ` [RFC PATCH 08/11] fs: remove READ_ONLY_THP_FOR_FS code Zi Yan
2026-03-23 19:06 ` [RFC PATCH 09/11] fs/btrfs: remove a comment referring to READ_ONLY_THP_FOR_FS Zi Yan
2026-03-23 19:47 ` David Sterba
2026-03-23 19:06 ` [RFC PATCH 10/11] selftests/mm: remove READ_ONLY_THP_FOR_FS test in khugepaged Zi Yan
2026-03-23 21:07 ` Matthew Wilcox
2026-03-24 9:04 ` David Hildenbrand (Arm)
2026-03-24 11:14 ` Zi Yan
2026-03-23 19:06 ` [RFC PATCH 11/11] selftests/mm: remove READ_ONLY_THP_FOR_FS test in guard-regions Zi Yan
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