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Mon, 03 Aug 2026 19:11:35 -0700 (PDT) Date: Tue, 4 Aug 2026 10:11:21 +0800 From: Kairui Song To: Johannes Weiner Cc: kasong@tencent.com, linux-mm@kvack.org, Andrew Morton , Muchun Song , Qi Zheng , Ying Huang , Chris Li , Baoquan He , Nico Pache , Usama Arif , Michal Hocko , Roman Gushchin , Shakeel Butt , David Hildenbrand , Lorenzo Stoakes , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Vlastimil Babka , Suren Baghdasaryan , Kemeng Shi , Nhat Pham , Youngjun Park , Zi Yan , Gregory Price , "Matthew Wilcox (Oracle)" , Baolin Wang , Ryan Roberts , Dev Jain , Lance Yang , Hugh Dickins , SeongJae Park , David Rientjes , Yu Zhao , Vernon Yang , Zicheng Wang , Chen Ridong , Tal Zussman , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: Re: [PATCH RFC 12/15] mm/smap: report workingset folios as referenced Message-ID: References: <20260804-mglru-fg-v1-0-4d8dad39dad6@tencent.com> <20260804-mglru-fg-v1-12-4d8dad39dad6@tencent.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Aug 03, 2026 at 09:21:33PM +0800, Johannes Weiner wrote: > On Tue, Aug 04, 2026 at 03:47:08AM +0800, Kairui Song via B4 Relay wrote: > > @@ -944,6 +944,22 @@ static void smaps_page_accumulate(struct mem_size_stats *mss, > > } > > } > > > > +static bool smap_check_folio_referenced(struct folio *folio) > > +{ > > + if (lru_gen_enabled()) > > + return folio_is_referenced(folio); > > + else > > + return folio_is_referenced_by_bit(folio); > > +} > > + > > +static void smap_clear_folio_referenced(struct folio *folio) > > +{ > > + if (lru_gen_enabled()) > > + folio_set_lru_refs(folio, 0); > > + else > > + folio_clear_referenced_by_bit(folio); > > +} > > I don't really understand this and the preceding 2 patches. > > What is the benefit of a "shared" ref/workingset state implementation > when you then still have separate APIs for querying & modifying? > > Switching some these callers from folio_test_workingset() to > folio_is_workingset()? But both functions continue to exist? > > Why not make versions of folio_test_workingset(), > folio_test_referenced(), folio_clear_referenced() etc. that do the > arbitration (bit ops on classic, refs ops on mglru) and leave callers > that are only interested in boolean states, like here, alone? > > folio_test_anon(), folio_test_lazyfree(), folio_test_swapcache() - > there are many examples where they don't just test a raw bit but > assess more complex, composed state. > Sound good, I just copied the folio_is/mark_workingset helper from my previous combined RFC, where I tried to drop PG_workingset hence used a standalone helper to convert the users one by one for easier audit and tracking. I think I can just replace the default helpers and have zero effect for CLRU. There are actually a few more helpers not used but introduced here, will drop these in V2. Thanks for the review!