From: "David Hildenbrand (Arm)" <david@kernel.org>
To: "Kiryl Shutsemau (Meta)" <kas@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Matthew Wilcox <willy@infradead.org>,
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Hugh Dickins <hughd@google.com>,
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Alexander Viro <viro@zeniv.linux.org.uk>,
Harry Yoo <harry@kernel.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
Miaohe Lin <linmiaohe@huawei.com>,
Naoya Horiguchi <nao.horiguchi@gmail.com>,
Oscar Salvador <osalvador@suse.de>,
"Liam R. Howlett" <liam@infradead.org>,
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Luis Chamberlain <mcgrof@kernel.org>,
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kernel-team@meta.com
Subject: Re: [RFC PATCH v2 04/18] mm: count the pages waiting for a grace period
Date: Mon, 9 Nov 2026 15:48:20 +0100 [thread overview]
Message-ID: <01605605-d6a9-44c6-a5b9-024f33d8c488@kernel.org> (raw)
In-Reply-To: <20261104130118.2507513-5-kas@kernel.org>
On 11/4/26 14:01, Kiryl Shutsemau (Meta) wrote:
> Deferred folios have refcount 0 and are not on the free lists, so no
> counter shows them. Memory that waits for a grace period is missing
> from the free count and from every LRU count.
>
> Count it per zone in NR_FREE_RCU_PAGES: nr_free_rcu in /proc/vmstat,
> free_rcu in show_free_areas(). Preparation for freeing the waiting
> pages sooner when they hold back memory that is needed.
Even if we switch to having this folio-specific internally, I think it will be
the right approach to expose this as NR_FREE_RCU_PAGES. (not NR_*FOLIOS, for
example, because we want the actual # pages)
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
--
Cheers,
David
next prev parent reply other threads:[~2026-11-09 14:48 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-04 13:00 [RFC PATCH v2 00/18] mm: read the page cache without folio references Kiryl Shutsemau (Meta)
2026-11-04 13:00 ` [RFC PATCH v2 01/18] mm: free PG_rcu_free folios only after an RCU grace period Kiryl Shutsemau (Meta)
2026-11-05 20:37 ` David Hildenbrand (Arm)
2026-11-06 10:23 ` Kiryl Shutsemau
2026-11-09 14:42 ` David Hildenbrand (Arm)
2026-11-04 13:00 ` [RFC PATCH v2 02/18] splice: don't steal page cache folios Kiryl Shutsemau (Meta)
2026-11-04 16:05 ` David Hildenbrand (Arm)
2026-11-05 14:55 ` Kiryl Shutsemau
2026-11-04 13:00 ` [RFC PATCH v2 03/18] fuse: don't move a folio with PG_rcu_free into a fuse file Kiryl Shutsemau (Meta)
2026-11-09 14:46 ` David Hildenbrand (Arm)
2026-11-04 13:01 ` [RFC PATCH v2 04/18] mm: count the pages waiting for a grace period Kiryl Shutsemau (Meta)
2026-11-09 14:48 ` David Hildenbrand (Arm) [this message]
2026-11-04 13:01 ` [RFC PATCH v2 05/18] mm: expedite the grace period when a CPU has many deferred frees Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 06/18] mm: free the pages waiting for a grace period before OOM Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 07/18] mm: free the pages waiting for a grace period before isolation fails Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 08/18] mm/compaction: free the migrated folios that wait for a grace period Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 09/18] mm/memory-failure: handle folios with PG_rcu_free Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 10/18] mm: have folio_mark_accessed() return whether the folio is hot Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 11/18] mm/filemap: mark a folio accessed in one place in filemap_read() Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 12/18] mm/filemap: set PG_rcu_free on the folios that reads keep coming back to Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 13/18] mm/filemap: read from the page cache without folio references Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 14/18] mm/filemap: read large folios " Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 15/18] mm/filemap: don't store f_ra.prev_pos for FMODE_RANDOM files Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 16/18] mm/shmem: count accesses to a folio the way filemap_read() does Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 17/18] mm/shmem: read without folio references Kiryl Shutsemau (Meta)
2026-11-04 13:01 ` [RFC PATCH v2 18/18] mm/filemap: add a debugfs switch for lockless page cache reads Kiryl Shutsemau (Meta)
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