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Thu, 17 Sep 2026 03:12:29 +0000 X-Mizu-Trace-ID: 03f180ae3d787af5 X-Migadu-Flow: FLOW_OUT Message-ID: <34ffedaf-8f98-48eb-b3a9-d42f273a261d@linux.dev> Date: Thu, 17 Sep 2026 11:12:20 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] mm/mglru: add tracepoint for scan_folios() To: Baoquan He 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 References: <20260911102939.2485750-1-ridong.chen@linux.dev> <20260911102939.2485750-3-ridong.chen@linux.dev> From: Ridong Chen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: hj1txu8gd59jnet87osuimw39q1kqfcp X-Rspamd-Queue-Id: F330A20008 X-HE-Tag: 1789614750-690292 X-HE-Meta: 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 4v/iqhUk Ws/JYEPUrXXPVrkjP4dA71A6Ej58YQ6nFaS9JsDV49mzu9J1c5gywt2az0ngftQAb7rFCqXmKsoPHJ/M7f7sdpUAixdPYozEKvlQcH2iUvv4SPR36f0wNI08R3akCGsUN7dNkLeUiXdHJ3zNlX01nb7Acq3DqAcshjaawS6qfnHu/W7A5Vrc7CAAglqsN8ok7KXqzqjtZZPoNyBtCkI1Eu/AfNDE0/yC+3eeTKZ6B4y0R3evUjx1YksTbaSN3LonfLNzJVe6XqXFKCdq8Mv1MXKHNHiwuiaNidkMlKkoS+qNI+onhtdrROycFllVMt7ctV0E+SXZfqsu9vAlK+ukN6sNUjsLTui8LEUNU Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/17/2026 9:07 AM, Baoquan He wrote: > 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. > Good. It works, I just tested it. Will add nid. > >> > >>>> >>>> >>>>> 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 >> -- Best regards Ridong