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charset="UTF-8" X-Stat-Signature: hbmbkk3ow1pr8bgd5w9ii8a9d4z9ds8u X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 86F4D4002D Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=fMmkaJuL; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf27.hostedemail.com: domain of 21cnbao@gmail.com designates 209.85.219.175 as permitted sender) smtp.mailfrom=21cnbao@gmail.com X-Rspam-User: X-HE-Tag: 1648021668-475782 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: On Sat, Mar 19, 2022 at 4:11 PM Yu Zhao wrote: > > On Fri, Mar 18, 2022 at 9:01 PM Barry Song <21cnbao@gmail.com> wrote: > > > > > +static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming) > > > +{ > > > + unsigned long old_flags, new_flags; > > > + int type = folio_is_file_lru(folio); > > > + struct lru_gen_struct *lrugen = &lruvec->lrugen; > > > + int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); > > > + > > > + do { > > > + new_flags = old_flags = READ_ONCE(folio->flags); > > > + VM_BUG_ON_FOLIO(!(new_flags & LRU_GEN_MASK), folio); > > > + > > > + new_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; > > > + new_gen = (old_gen + 1) % MAX_NR_GENS; > > > > new_gen is assigned twice, i assume you mean > > old_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; > > new_gen = (old_gen + 1) % MAX_NR_GENS; > > > > or do you always mean new_gen = lru_gen_from_seq(min_seq) + 1? > > Thanks a lot for your attention to details! > > The first line should be in the next patch but I overlooked during the > last refactoring: Thanks for the clarification. So an unmapped file-backed page which is accessed only by system call will always be in either min_seq or min_seq + 1? it has no chance to be in max_seq like a faulted-in mapped file page? > > new_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; > + /* folio_update_gen() has promoted this page? */ > + if (new_gen >= 0 && new_gen != old_gen) > + return new_gen; > + > new_gen = (old_gen + 1) % MAX_NR_GENS; Thanks Barry