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Mon, 15 Dec 2025 13:14:01 -0800 (PST) Date: Mon, 15 Dec 2025 16:13:57 -0500 From: Johannes Weiner To: Chen Ridong Cc: akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, zhengqi.arch@bytedance.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, lujialin4@huawei.com, zhongjinji@honor.com Subject: Re: [PATCH -next 3/5] mm/mglru: extend shrink_one for both lrugen and non-lrugen Message-ID: <20251215211357.GF905277@cmpxchg.org> References: <20251209012557.1949239-1-chenridong@huaweicloud.com> <20251209012557.1949239-4-chenridong@huaweicloud.com> Precedence: bulk X-Mailing-List: cgroups@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: <20251209012557.1949239-4-chenridong@huaweicloud.com> On Tue, Dec 09, 2025 at 01:25:55AM +0000, Chen Ridong wrote: > From: Chen Ridong > > Currently, flush_reclaim_state is placed differently between > shrink_node_memcgs and shrink_many. shrink_many (only used for gen-LRU) > calls it after each lruvec is shrunk, while shrink_node_memcgs calls it > only after all lruvecs have been shrunk. > > This patch moves flush_reclaim_state into shrink_node_memcgs and calls it > after each lruvec. This unifies the behavior and is reasonable because: > > 1. flush_reclaim_state adds current->reclaim_state->reclaimed to > sc->nr_reclaimed. > 2. For non-MGLRU root reclaim, this can help stop the iteration earlier > when nr_to_reclaim is reached. > 3. For non-root reclaim, the effect is negligible since flush_reclaim_state > does nothing in that case. > > After moving flush_reclaim_state into shrink_node_memcgs, shrink_one can be > extended to support both lrugen and non-lrugen paths. It will call > try_to_shrink_lruvec for lrugen root reclaim and shrink_lruvec otherwise. > > Signed-off-by: Chen Ridong > --- > mm/vmscan.c | 57 +++++++++++++++++++++-------------------------------- > 1 file changed, 23 insertions(+), 34 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 584f41eb4c14..795f5ebd9341 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -4758,23 +4758,7 @@ static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) > return nr_to_scan < 0; > } > > -static void shrink_one(struct lruvec *lruvec, struct scan_control *sc) > -{ > - unsigned long scanned = sc->nr_scanned; > - unsigned long reclaimed = sc->nr_reclaimed; > - struct pglist_data *pgdat = lruvec_pgdat(lruvec); > - struct mem_cgroup *memcg = lruvec_memcg(lruvec); > - > - try_to_shrink_lruvec(lruvec, sc); > - > - shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, sc->priority); > - > - if (!sc->proactive) > - vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned, > - sc->nr_reclaimed - reclaimed); > - > - flush_reclaim_state(sc); > -} > +static void shrink_one(struct lruvec *lruvec, struct scan_control *sc); > > static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc) > { > @@ -5760,6 +5744,27 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat, > return inactive_lru_pages > pages_for_compaction; > } > > +static void shrink_one(struct lruvec *lruvec, struct scan_control *sc) > +{ > + unsigned long scanned = sc->nr_scanned; > + unsigned long reclaimed = sc->nr_reclaimed; > + struct pglist_data *pgdat = lruvec_pgdat(lruvec); > + struct mem_cgroup *memcg = lruvec_memcg(lruvec); > + > + if (lru_gen_enabled() && root_reclaim(sc)) > + try_to_shrink_lruvec(lruvec, sc); > + else > + shrink_lruvec(lruvec, sc); Yikes. So we end up with: shrink_node_memcgs() shrink_one() if lru_gen_enabled && root_reclaim(sc) try_to_shrink_lruvec(lruvec, sc) else shrink_lruvec() if lru_gen_enabled && !root_reclaim(sc) lru_gen_shrink_lruvec(lruvec, sc) try_to_shrink_lruvec() I think it's doing too much at once. Can you get it into the following shape: shrink_node_memcgs() for each memcg: if lru_gen_enabled: lru_gen_shrink_lruvec() else shrink_lruvec() and handle the differences in those two functions? Then look for overlap one level down, and so forth.