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Thu, 17 Sep 2026 01:07:59 +0000 X-Mizu-Trace-ID: 18a8981867d871f6 X-Migadu-Flow: FLOW_OUT Date: Thu, 17 Sep 2026 09:07:54 +0800 From: Baoquan He To: Ridong Chen Cc: Steven Rostedt , Masami Hiramatsu , Andrew Morton , Johannes Weiner , Mathieu Desnoyers , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baolin Wang , David Hildenbrand , Michal Hocko , Lorenzo Stoakes , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, "open list:MEMORY MANAGEMENT - MGLRU (MULTI-GEN LRU)" , Ridong Chen Subject: Re: [PATCH v2 2/3] mm/mglru: add tracepoint for scan_folios() Message-ID: References: <20260911102939.2485750-1-ridong.chen@linux.dev> <20260911102939.2485750-3-ridong.chen@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 1D1521C0005 X-Stat-Signature: xpk8k7jq8ts9ouz4ss14ki7pf1cm3nd6 X-Rspamd-Server: rspam01 X-HE-Tag: 1789607290-265235 X-HE-Meta: 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 pbpzTg/O Fnplzz2IApyR3MR05OQUgWFxq6pFd3IrCYD7n/S1cSJ2o+PsOSxaEYIPYr/kkiQjlN9kQa7iGtA61Slsd/RwTDdjwJ64OulJwuMURJjcFRIcf/c+YCxYrngvywD+GD6ifOML8w59ocsXBPjbVbOLacxoanbJG7s1A03hN34B+2ME5WvxLijdMoLg+r8r1E6ipwFOLudHk5JwWCRjxw7sm6wENqMznmeS7ez99/RPJDdQLazmGE+kEwYDQY+2axsZAtzVcsnbXGmCnn6Xd8wd2i7QJs20ExYPbtT9hkqHpKPoldZYuzbYMD6vteV+92o5WUnI6L27pzf+tnOBm5OgxZzzTMQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 09/16/26 at 08:17pm, Ridong Chen wrote: > > > On 9/16/2026 10:14 AM, Baoquan He wrote: > > On 09/15/26 at 08:17pm, Ridong Chen wrote: > > > > > > > > > On 9/15/2026 7:14 PM, Baoquan He wrote: > > > > On 09/11/26 at 06:29pm, Ridong Chen wrote: > > > > > From: Ridong Chen > > > > ...snip... > > > > > --- > > > > > include/trace/events/vmscan.h | 63 +++++++++++++++++++++++++++++++++++ > > > > > mm/vmscan.c | 6 ++++ > > > > > 2 files changed, 69 insertions(+) > > > > > > > > > > diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h > > > > > index 8a872990b4be..5defa8f6719c 100644 > > > > > --- a/include/trace/events/vmscan.h > > > > > +++ b/include/trace/events/vmscan.h > > > > > @@ -392,6 +392,69 @@ TRACE_EVENT(mm_vmscan_lru_isolate, > > > > > __print_symbolic(__entry->lru, LRU_NAMES)) > > > > > ); > > > > > +TRACE_EVENT(mm_mglru_scan_folios, > > > > > + > > > > > + TP_PROTO(struct lruvec *lruvec, > > > > > + int highest_zoneidx, > > > > > + int order, > > > > > + unsigned long nr_requested, > > > > > + unsigned long nr_scanned, > > > > > + unsigned long nr_sorted, > > > > > + unsigned long nr_skipped, > > > > > + unsigned long nr_taken, > > > > > + int lru, > > > > > + unsigned long max_seq, > > > > > + int tier, > > > > > + unsigned long min_seq), > > > > > > > > > > Thank you for your review. > > > > > > > Do we need show nid? Guess phone vendor doesn't care about multi-NUMA > > > > system. > > > > > > > > > > Eh, nid is not an mglru-specific key. Since there are 12 elements here, it > > > can't be added here. > > > > Hmm, we print memcg_id but not nid, it may not be so clear. How do you ^~~~ typo, s/not/no/ > > differentiate several lruvec-s on one memcg? I am not very familiar with > > trace mechanism, do we have a element number limit? > > > > Yes, it will fail to compile if there are more than 12 elements. > > With AI's help, see > > include/trace/bpf_probe.h > ``` > 30 #define __CAST1(a,...) __CAST_TO_U64(a) > 31 #define __CAST2(a,...) __CAST_TO_U64(a), __CAST1(__VA_ARGS__) > 32 #define __CAST3(a,...) __CAST_TO_U64(a), __CAST2(__VA_ARGS__) > 33 #define __CAST4(a,...) __CAST_TO_U64(a), __CAST3(__VA_ARGS__) > 34 #define __CAST5(a,...) __CAST_TO_U64(a), __CAST4(__VA_ARGS__) > 35 #define __CAST6(a,...) __CAST_TO_U64(a), __CAST5(__VA_ARGS__) > 36 #define __CAST7(a,...) __CAST_TO_U64(a), __CAST6(__VA_ARGS__) > 37 #define __CAST8(a,...) __CAST_TO_U64(a), __CAST7(__VA_ARGS__) > 38 #define __CAST9(a,...) __CAST_TO_U64(a), __CAST8(__VA_ARGS__) > 39 #define __CAST10(a,...) __CAST_TO_U64(a), __CAST9(__VA_ARGS__) > 40 #define __CAST11(a,...) __CAST_TO_U64(a), __CAST10(__VA_ARGS__) > 41 #define __CAST12(a,...) __CAST_TO_U64(a), __CAST11(__VA_ARGS__) > /* tracepoints with more than 12 arguments will hit build error */ > ``` > > > Imagine I only want to trace this function, now I can see memcg_id, > > zone_idex, while don't know node/lruvec, that's a little pitty. Just my > > personal opinion, I could miss anything. > > > > Yeah, you are right. In my personal experience, I always enable > trace_mm_vmscan_lru_isolate and trace_mm_vmscan_lru_shrink_inactive, which > contain node_id. So we can see how the lruvec is scanned and shrunk, and we > can get node_id from trace_mm_vmscan_lru_shrink_inactive. I am not arguing > that this is exactly the 'correct' way to use these tracepoints, but I think > it is a common usage. > > I am open to that. If we want to record node_id, we have to remove an > element. Maybe tier? But I would strongly recommend record memcg_id, we > frequently need to check the reclaim behavior of a memcg, and most of our Sorry, that's my typo which could cause misunderstanding. I meant "we print memcg_id but no nid, it may not be so clear". I agree with you that memcg_id is undispensable. > scenarios are non-NUMA. Understood, mobile phone mostly is non-NUMA, while server is different. About adding nid, I cousulted AI too, it says it's doable. It says The 12-argument limit only counts the TP_PROTO arguments (that's the BPF __CAST12/bpf_trace_run12 path), not the __entry fields in TP_STRUCT__entry. And nid doesn't have to be a 13th argument at all. We already pass lruvec, so nid can be derived from it in TP_fast_assign with lruvec_pgdat(lruvec)->node_id. e.g. for mm_mglru_scan_folios: TP_STRUCT__entry( __field(u64, memcg_id) __field(int, nid) __field(int, highest_zoneidx) __field(int, order) __field(unsigned long, nr_requested) __field(unsigned long, nr_scanned) __field(unsigned long, nr_sorted) __field(unsigned long, nr_skipped) __field(unsigned long, nr_taken) __field(int, lru) __field(unsigned long, max_seq) __field(int, tier) __field(unsigned long, min_seq) ), TP_fast_assign( __entry->memcg_id = mem_cgroup_id(lruvec_memcg(lruvec)); __entry->nid = lruvec_pgdat(lruvec)->node_id; __entry->highest_zoneidx = highest_zoneidx; ... ), TP_printk("memcg_id=%llu nid=%d classzone=%d order=%d ...", __entry->memcg_id, __entry->nid, __entry->highest_zoneidx, ...) lruvec_pgdat() comes from include/linux/mmzone.h, which vmscan.h already pulls in via linux/mm.h, so no extra include is needed. The same pattern applies to mm_mglru_inc_max_seq in patch 3 if you want nid there too. I didn't try it though, please feel free to give it a shot. Thanks Baoquan > > > > > > > > > > > And I checked v1 thread, seems Steven suggested to move the two int to > > > > avoid extra padding. > > > > > > > > > > Yeah, I will update it. I updated v2 to fix Sashiko's issue, before Steven > > > had any comment. > > > > > > > > > > > + > > > > > + TP_ARGS(lruvec, highest_zoneidx, order, nr_requested, nr_scanned, > > > > > + nr_sorted, nr_skipped, nr_taken, lru, max_seq, tier, min_seq), > > > > > + > > > > > + TP_STRUCT__entry( > > > > > + __field(u64, memcg_id) > > > > > + __field(int, highest_zoneidx) > > > > > + __field(int, order) > > > > > + __field(unsigned long, nr_requested) > > > > > + __field(unsigned long, nr_scanned) > > > > > + __field(unsigned long, nr_sorted) > > > > > + __field(unsigned long, nr_skipped) > > > > > + __field(unsigned long, nr_taken) > > > > > + __field(int, lru) > > > > > + __field(unsigned long, max_seq) > > > > > + __field(int, tier) > > > > > + __field(unsigned long, min_seq) > > > > > + ), > > > > > + > > > > > + TP_fast_assign( > > > > > + __entry->memcg_id = mem_cgroup_id(lruvec_memcg(lruvec)); > > > > > + __entry->highest_zoneidx = highest_zoneidx; > > > > > + __entry->order = order; > > > > > + __entry->nr_requested = nr_requested; > > > > > + __entry->nr_scanned = nr_scanned; > > > > > + __entry->nr_sorted = nr_sorted; > > > > > + __entry->nr_skipped = nr_skipped; > > > > > + __entry->nr_taken = nr_taken; > > > > > + __entry->lru = lru; > > > > > + __entry->max_seq = max_seq; > > > > > + __entry->tier = tier; > > > > > + __entry->min_seq = min_seq; > > > > > + ), > > > > > + > > > > > + TP_printk("memcg_id=%llu classzone=%d order=%d nr_requested=%lu nr_scanned=%lu nr_sorted=%lu nr_skipped=%lu nr_taken=%lu lru=%s max_seq=%lu tier=%d min_seq=%lu", > > > > > + __entry->memcg_id, > > > > > + __entry->highest_zoneidx, > > > > > + __entry->order, > > > > > + __entry->nr_requested, > > > > > + __entry->nr_scanned, > > > > > + __entry->nr_sorted, > > > > > + __entry->nr_skipped, > > > > > + __entry->nr_taken, > > > > > + __print_symbolic(__entry->lru, LRU_NAMES), > > > > > + __entry->max_seq, > > > > > + __entry->tier, > > > > > + __entry->min_seq) > > > > > +); > > > > > + > > > > > TRACE_EVENT(mm_vmscan_write_folio, > > > > > TP_PROTO(struct folio *folio), > > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > > > > index 2554a6513aa8..67f59aa73fb9 100644 > > > > > --- a/mm/vmscan.c > > > > > +++ b/mm/vmscan.c > > > > > @@ -4876,6 +4876,12 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, > > > > > trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, > > > > > scanned, skipped, isolated, > > > > > type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON); > > > > > + trace_mm_mglru_scan_folios(lruvec, > > > > > + sc->reclaim_idx, sc->order, nr_to_scan, > > > > > + scanned, sorted, skipped, isolated, > > > > > + type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON, > > > > > + lrugen->max_seq, tier, > > > > > + lrugen->min_seq[type]); > > > > > > > > And seems Steven also suggested to calculate lru, max_seq, min_seq in > > > > TP_fast_assign() in v1 which could be missed. > > > > > > > > > > Thanks, I will update it following Steven's suggestions. > > > > > > > > > > TP_fast_assign( > > > > __entry->memcg_id = mem_cgroup_id(lruvec_memcg(lruvec)); > > > > __entry->highest_zoneidx = sc->reclaim_idx; > > > > __entry->order = sc->order; > > > > __entry->nr_requested = nr_requested; > > > > __entry->nr_scanned = nr_scanned; > > > > __entry->nr_sorted = nr_sorted; > > > > __entry->nr_skipped = nr_skipped; > > > > __entry->nr_taken = nr_taken; > > > > __entry->lru = type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON; > > > > __entry->max_seq = lrugen->max_seq; > > > > __entry->tier = tier; > > > > __entry->min_seq = lrugen->min_seq; > > > > ), > > > > > > > > > > However, 'sc' is an internal structure, so sc->order cannot be accessed in > > > TP_fast_assign(), and I don't think it is worth making scan_control an > > > external structure just for this. > > > > Agree. > > > > > > > > > > > > > > *isolatedp = isolated; > > > > > return scanned; > > > > > -- > > > > > 2.34.1 > > > > > > > > > > > -- > > > Best regards > > > Ridong > > > > > -- > Best regards > Ridong >