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Mon, 19 Oct 2026 04:24:17 +0000 X-Mizu-Trace-ID: a7533987bd4880b4 X-Migadu-Flow: FLOW_OUT From: Ridong Chen To: Steven Rostedt , Masami Hiramatsu , Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Dave Chinner Cc: Mathieu Desnoyers , Muchun Song , Qi Zheng , David Hildenbrand , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, bpf@vger.kernel.org, Ridong Chen , Ridong Chen Subject: [PATCH v4 9/9] mm/mglru: add tracepoint for inc_max_seq() Date: Mon, 19 Oct 2026 12:23:08 +0800 Message-Id: <20261019042308.2372396-4-ridong.chen@linux.dev> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20261019034426.2354049-1-ridong.chen@linux.dev> References: <20261019034426.2354049-1-ridong.chen@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 41B678000A X-Stat-Signature: s66w9yef3soud7h1nnx7yqph1g6kzhse X-Rspam-User: X-HE-Tag: 1792383859-56356 X-HE-Meta: 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 /fJYwU3V Cp9cRBhq0FCJbbLCWQ4K8qWSUp0lg1JeqAzB3FWLhP2UpAeiVfVNfaVuygtGbp8OFXUJnLzGxovyfAAmejhVpoUgdrgotQIcSJs5VSY9a6NcZ4/B7kRaJsO9zAjCIaF1kJ1R2/1KxHHkbYE1GUQ7zLJTrt0vb4WAn7XaV+hb2HCSHI6OivzR9TWTMsionuVvMbtVPLjz58oJd2hPNVWUjJRMkGsdgApY/JM5s5r8Kvrt2oO13YWOYnBYWvvbiG1eR0MkLLwAz3xR0hI15NLTbPCQ9ucYBD12Eg7NGLzynFdfDWTusDBI5A/oc7IIfqFNROxnoeS7HxQZspcYxfbgcEWijKg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Ridong Chen Aging in MGLRU advances max_seq via inc_max_seq(), creating a new youngest generation. There is currently no tracepoint on this path, so the moment a new generation is created, and how the min_seq of each type trails behind it, cannot be observed as it happens. Add mm_mglru_inc_max_seq, emitted right after max_seq is bumped while the lruvec lock is still held, with the node id, memcg id, the new max_seq, the anon and file min_seq, and the number of pages in each generation for both types, summed over zones and clamped to >= 0 the same way the debugfs lru_gen file reports them. The nr_anon/nr_file arrays are indexed by generation slot, so the emitted max_seq/min_seq say which slot holds which seq. They are printed with __print_array(), so the output is hex and its length follows MAX_NR_GENS automatically. Only the lruvec is passed in; all of the above is collected in TP_fast_assign(), so inc_max_seq() does no extra work when the event is disabled. Paired with mm_mglru_scan_folios it makes the full aging-to-eviction window observable per memcg. Assisted-by: LLM Signed-off-by: Ridong Chen --- mm/trace_vmscan.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++ mm/vmscan.c | 2 ++ 2 files changed, 49 insertions(+) diff --git a/mm/trace_vmscan.h b/mm/trace_vmscan.h index 8148b8224422..cddf42b5849a 100644 --- a/mm/trace_vmscan.h +++ b/mm/trace_vmscan.h @@ -456,6 +456,53 @@ TRACE_EVENT(mm_mglru_scan_folios, __entry->min_seq) ); +TRACE_EVENT(mm_mglru_inc_max_seq, + + TP_PROTO(struct lruvec *lruvec), + + TP_ARGS(lruvec), + + TP_STRUCT__entry( + __field(u64, memcg_id) + __field(unsigned long, max_seq) + __field(unsigned long, anon_min_seq) + __field(unsigned long, file_min_seq) + __array(unsigned long, nr_anon, MAX_NR_GENS) + __array(unsigned long, nr_file, MAX_NR_GENS) + __field(int, nid) + ), + + TP_fast_assign( + struct lru_gen_folio *lrugen = &lruvec->lrugen; + int gen, zone; + + __entry->memcg_id = mem_cgroup_id(lruvec_memcg(lruvec)); + __entry->max_seq = lrugen->max_seq; + __entry->anon_min_seq = lrugen->min_seq[LRU_GEN_ANON]; + __entry->file_min_seq = lrugen->min_seq[LRU_GEN_FILE]; + /* summed over zones and clamped to >= 0, as debugfs lru_gen does */ + for (gen = 0; gen < MAX_NR_GENS; gen++) { + __entry->nr_anon[gen] = 0; + __entry->nr_file[gen] = 0; + for (zone = 0; zone < MAX_NR_ZONES; zone++) { + __entry->nr_anon[gen] += + max(lrugen->nr_pages[gen][LRU_GEN_ANON][zone], 0L); + __entry->nr_file[gen] += + max(lrugen->nr_pages[gen][LRU_GEN_FILE][zone], 0L); + } + } + __entry->nid = lruvec_pgdat(lruvec)->node_id; + ), + + TP_printk("nid=%d memcg_id=%llu max_seq=%lu anon_min_seq=%lu file_min_seq=%lu nr_anon=%s nr_file=%s", + __entry->nid, + __entry->memcg_id, + __entry->max_seq, + __entry->anon_min_seq, + __entry->file_min_seq, + __print_array(__entry->nr_anon, MAX_NR_GENS, sizeof(unsigned long)), + __print_array(__entry->nr_file, MAX_NR_GENS, sizeof(unsigned long))) +); #endif /* CONFIG_LRU_GEN */ TRACE_EVENT(mm_vmscan_write_folio, diff --git a/mm/vmscan.c b/mm/vmscan.c index d459678c5ee5..7b9b1aca5c88 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4129,6 +4129,8 @@ static bool inc_max_seq(struct lruvec *lruvec, unsigned long seq, int swappiness WRITE_ONCE(lrugen->timestamps[next], jiffies); /* make sure preceding modifications appear */ smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1); + + trace_mm_mglru_inc_max_seq(lruvec); unlock: lruvec_unlock_irq(lruvec); -- 2.34.1