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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776151231; bh=ROcL0Ax/9HIDfTXMPTJFEEgwD3u2oJr3p1yQIodv5TI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=LwMpWIBHOtgSKW/PkenJ2SX4pvgOIrGM68t435fiq5y/qZVDMpXR/c8VDxPVrGUhD cKHEACGz8/et2gFcRHGL25ix3FB9tb7L9h31YzYWnEAnfRL4xyubkLPQTddceYOdgC Q+K3xDBzY1sgw4NUe1QpxOvViColPDQUNjVQV2yWHHEomDI5mIs/WA3os9/hesdstL 0ydiJ/jgTXnFpsw6rLawcHulTEwF3RN7NqOOlpMOttcJkGlf7sRKLleiBEKIngRWPm yUjEVgs/3ix8jOSs2KgCMDXMdff4Z1R23JoqHTaK3sAo3WzUG1ZhjREKuay7gGSBuN BGvAIDWnaYKYA== Message-ID: <0c22f74a-ff3d-405b-8d9e-a7222f5b9dfe@kernel.org> Date: Tue, 14 Apr 2026 09:20:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 2/3] mm: process_mrelease: skip LRU movement for exclusive file folios To: Minchan Kim , akpm@linux-foundation.org Cc: mhocko@suse.com, brauner@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, surenb@google.com, timmurray@google.com References: <20260413223948.556351-1-minchan@kernel.org> <20260413223948.556351-3-minchan@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: F107340004 X-Stat-Signature: 69zhcbt5gq6dcwhwr5j48imxybapdex8 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1776151232-545364 X-HE-Meta: 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 MzjXqrPH YkLAfpkSpcO9klWJP7UGWvclu5hyb+rBNFIE3xCuUs+EuKwMfoDDd61rBFCbSx2GDrgNS6h6tt6Tm2/Jll1XSeV5Fu3JqnSoJt4zLu2zflPz6ndBvNfHpWlFyeyNfq9LZhS5Vl3ztaJ9EOK9kQEH4ek71GiHyRunHymk6FiUacq1t/bsrXv7DvGQ8iYOLjCXo6pZBu7TzwB+rfzYDh4tyJ7GZV0jgw8InQiGq0WLKWuYyRIHATfkzf5MgLGJ4atzWGqQOnfFEI0bErEIPA2ZUDtvN5YDLwi0A1aOcnoflMA6AAMaQCIyBG8JN4JQzSeXS8OPwA2P3t3Qu6d8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/14/26 00:39, Minchan Kim wrote: > For the process_mrelease reclaim, skip LRU handling for exclusive > file-backed folios since they will be freed soon so pointless > to move around in the LRU. > > This avoids costly LRU movement which accounts for a significant portion > of the time during unmap_page_range. > > - 91.31% 0.00% mmap_exit_test [kernel.kallsyms] [.] exit_mm > exit_mm > __mmput > exit_mmap > unmap_vmas > - unmap_page_range > - 55.75% folio_mark_accessed > + 48.79% __folio_batch_add_and_move > 4.23% workingset_activation > + 12.94% folio_remove_rmap_ptes > + 9.86% page_table_check_clear > + 3.34% tlb_flush_mmu > 1.06% __page_table_check_pte_clear > > Signed-off-by: Minchan Kim > --- > mm/memory.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 2f815a34d924..25e17893c919 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1640,6 +1640,8 @@ static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb, > bool delay_rmap = false; > > if (!folio_test_anon(folio)) { > + bool skip_mark_accessed; > + > ptent = get_and_clear_full_ptes(mm, addr, pte, nr, tlb->fullmm); > if (pte_dirty(ptent)) { > folio_mark_dirty(folio); > @@ -1648,7 +1650,16 @@ static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb, > *force_flush = true; > } > } > - if (pte_young(ptent) && likely(vma_has_recency(vma))) > + > + /* > + * For the process_mrelease reclaim, skip LRU handling for exclusive > + * file-backed folios since they will be freed soon so pointless > + * to move around in the LRU. > + */ > + skip_mark_accessed = mm_flags_test(MMF_UNSTABLE, mm) && > + folio_mapcount(folio) < 2; folio_mapcount() is most certainly the wrong thing to use if you want to handle large folios properly. Maybe !folio_likely_mapped_shared() is what you are looking for. Maybe. -- Cheers, David