Re: [PATCH v2 2/3] mm/mglru: add tracepoint for scan_folios()

[Ridong Chen <ridong.chen@linux.dev>]

On 9/15/2026 7:14 PM, Baoquan He wrote:
> On 09/11/26 at 06:29pm, Ridong Chen wrote:
>> From: Ridong Chen <chenridong@xiaomi.com>
> ...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.


> 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.

> 
>>   
>>   	*isolatedp = isolated;
>>   	return scanned;
>> -- 
>> 2.34.1
>>

-- 
Best regards
Ridong