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Tue, 14 Oct 2025 05:23:36 -0700 (PDT) Date: Tue, 14 Oct 2025 12:23:35 +0000 From: Wei Yang To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, Andrew Morton , "Matthew Wilcox (Oracle)" , Tejun Heo , Zefan Li , Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , Jonathan Corbet , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Muchun Song , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn Subject: Re: [PATCH v3 20/20] mm: stop maintaining the per-page mapcount of large folios (CONFIG_NO_PAGE_MAPCOUNT) Message-ID: <20251014122335.dpyk5advbkioojnm@master> Reply-To: Wei Yang References: <20250303163014.1128035-1-david@redhat.com> <20250303163014.1128035-21-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250303163014.1128035-21-david@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam05 X-Stat-Signature: gd4ak5b4fpg1zccc39tr5hhecgye1xq3 X-Rspam-User: X-Rspamd-Queue-Id: BEF2520004 X-HE-Tag: 1760444618-46683 X-HE-Meta: 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 2tSJ1H4e 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 03, 2025 at 05:30:13PM +0100, David Hildenbrand wrote: [...] >@@ -1678,6 +1726,22 @@ static __always_inline void __folio_remove_rmap(struct folio *folio, > break; > case RMAP_LEVEL_PMD: > case RMAP_LEVEL_PUD: >+ if (IS_ENABLED(CONFIG_NO_PAGE_MAPCOUNT)) { >+ last = atomic_add_negative(-1, &folio->_entire_mapcount); >+ if (level == RMAP_LEVEL_PMD && last) >+ nr_pmdmapped = folio_large_nr_pages(folio); >+ nr = folio_dec_return_large_mapcount(folio, vma); >+ if (!nr) { >+ /* Now completely unmapped. */ >+ nr = folio_large_nr_pages(folio); >+ } else { >+ partially_mapped = last && >+ nr < folio_large_nr_pages(folio); Hi, David Do you think this is better to be? partially_mapped = last && nr < nr_pmdmapped; As commit 349994cf61e6 mentioned, we don't support partially mapped PUD-sized folio yet. Not sure what I missed here. >+ nr = 0; >+ } >+ break; >+ } >+ > folio_dec_large_mapcount(folio, vma); > last = atomic_add_negative(-1, &folio->_entire_mapcount); > if (last) { >-- >2.48.1 > -- Wei Yang Help you, Help me