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Wed, 18 Oct 2023 19:40:05 -0700 (PDT) MIME-Version: 1.0 References: <20231018082104.3918770-1-link@vivo.com> <20231018082104.3918770-3-link@vivo.com> In-Reply-To: From: Yu Zhao Date: Wed, 18 Oct 2023 20:39:28 -0600 Message-ID: Subject: Re: [PATCH 2/2] mm: multi-gen lru: fix stat count To: Huan Yang Cc: Steven Rostedt , Masami Hiramatsu , Andrew Morton , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, opensource.kernel@vivo.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C1102A0022 X-Rspam-User: X-Stat-Signature: wq5jaxq3ctz7utx1qzubg388y39xy1qm X-Rspamd-Server: rspam03 X-HE-Tag: 1697683206-43771 X-HE-Meta: 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 IO4Xd/4e K6eJCj1g+77esh4DdevOKOFMxt8Ei1sILkRRZ3QTwU8WC3vNkKIveOmZc1wydh3My0yy/YzzehRBm69dYZ1mmZVdfDoJ2/MNJhmpPZkkfsqCE3hWHkpERYNdMRNlXO8qdP1zTU5CA+mM0VGNcLaPN8tUs+wvXG7rmA/6iIhJ2cRZEjNgmT1bSL2UML4/QoS47MgjiiMhNZHDwBufhHknqp4eP0Wyp7BW+YCep0vX0RzPZ0yFa2bR5y3eGADaOuhOHvd6PaeObLReQG679RB+T4FspY0wnCXCcl123 X-Bogosity: Ham, tests=bogofilter, spamicity=0.005272, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 18, 2023 at 8:17=E2=80=AFPM Huan Yang wrote: > > Hi Yu Zhao, > > Thanks for your reply. > > =E5=9C=A8 2023/10/19 0:21, Yu Zhao =E5=86=99=E9=81=93: > > On Wed, Oct 18, 2023 at 2:22=E2=80=AFAM Huan Yang wrote= : > >> For multi-gen lru reclaim in evict_folios, like shrink_inactive_list, > >> gather folios which isolate to reclaim, and invoke shirnk_folio_list. > >> > >> But, when complete shrink, it not gather shrink reclaim stat into sc, > >> we can't get info like nr_dirty\congested in reclaim, and then > >> control writeback, dirty number and mark as LRUVEC_CONGESTED, or > >> just bpf trace shrink and get correct sc stat. > >> > >> This patch fix this by simple copy code from shrink_inactive_list when > >> end of shrink list. > > MGLRU doesn't try to write back dirt file pages in the reclaim path -- > > it filters them out in sort_folio() and leaves them to the page > Nice to know this, sort_folio() filters some folio indeed. > But, I want to know, if we touch some folio in shrink_folio_list(), may s= ome > folio become dirty or writeback even if sort_folio() filter then? Good question: in that case MGLRU still doesn't try to write those folios back because isolate_folio() cleared PG_reclaim and shrink_folio_list() checks PG_reclaim: if (folio_test_dirty(folio)) { /* * Only kswapd can writeback filesystem folios * to avoid risk of stack overflow. But avoid * injecting inefficient single-folio I/O into * flusher writeback as much as possible: only * write folios when we've encountered many * dirty folios, and when we've already scanned * the rest of the LRU for clean folios and see * the same dirty folios again (with the reclaim * flag set). */ if (folio_is_file_lru(folio) && (!current_is_kswapd() || !folio_test_reclaim(folio) || !test_bit(PGDAT_DIRTY, &pgdat->flags))) {