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To fix this, modify it to print nr_to_scan as isolate_lru_folios >>>> does. >>>> >>>> Fixes: 8c2214fc9a47 ("mm: multi-gen LRU: reuse some legacy trace events") >>>> Signed-off-by: Chen Ridong >>>> --- >>>>    mm/vmscan.c | 2 +- >>>>    1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>>> index fddd168a9737..8cfafd50a7a8 100644 >>>> --- a/mm/vmscan.c >>>> +++ b/mm/vmscan.c >>>> @@ -4601,7 +4601,7 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, >>>>        count_memcg_events(memcg, item, isolated); >>>>        count_memcg_events(memcg, PGREFILL, sorted); >>>>        __count_vm_events(PGSCAN_ANON + type, isolated); >>>> -    trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, MAX_LRU_BATCH, >>>> +    trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, >>>>                    scanned, skipped, isolated, >>> >>> We do that in isolate_lru_folios(). >>> >>> Given that we do >>> >>>      int remaining = min(nr_to_scan, MAX_LRU_BATCH); >>> >>> and effectively cap it, I wonder if we would want to trace that capped valued instead of >>> MAX_LRU_BATCH. >>> >> >> I prefer tracing nr_to_scan, as it reflects the original target number of pages we intended to scan. > > But it's misleading, because we're also tracing "scanned, skipped, isolated", and one might wonder > how it relates to nr_to_scan? > >> Even if nr_to_scan exceeds MAX_LRU_BATCH, we can still deduce that it was effectively capped by >> examining the actual scanned, skipped, or isolated counts. However, if we trace min(nr_to_scan, >> MAX_LRU_BATCH) instead, we would lose visibility into what the original nr_to_scan value was. > > Is that really required for the purpose we are tracing here? > Thank you David, I've seen Lance's response and agree with your point. Using min(nr_to_scan, MAX_LRU_BATCH) would indeed be more appropriate for the trace, as it reflects the actual capped value used during scanning. I'll update the patch accordingly. -- Best regards, Ridong