Hi Park: On 2021/11/10 下午9:16, SeongJae Park wrote: > On Wed, 10 Nov 2021 20:13:14 +0800 Xin Hao wrote: > >> In patch "mm/damon: add a tracepoint", it adds a >> tracepoint for DAMON, it can monitor each region >> for each aggregation interval, Now the region add >> a new 'age' variable, some primitive would calculate >> the priority of each region as a weight, there put it >> into tracepoint, so we can easily track the change of >> its value through perf or damon-tools. > DAMON calculates the age using the address range and nr_accesses of the region, > which are already in the tracepoint. In other words, user space can calculate > the age on their own. Therefore I thought putting age in the tracepoint as > adding unnecessary information, at the moment of the implementation. > > Of course, I would missing some use cases that need this information in the > tracepoint. Furthermore, adding just one more value in the tracepoint wouldn't > incur a real issue. But, I'd like to know why this is necessary and how much > benefit it provides. Xin, could you please share that? I think these two variables nr_access &  age have different meanings, the nr_access only reflect the period of  sample_interval,  We may be able to get the change of age through continuous long-term sampling, But I think this is not very convenient. We only need to observe the change of age value a small number of times to replace the continue sampling of the region. For example, age has been increasing to 141, but nr_access shows a value of 0 at a certain time. Through this，we can conclude that the region has a very low nr_access value for a long time. This datas that  i used perf tool to record & script *       kdamond.0  8282 [007]   664.187237: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 305254400-597266432: 0 140** **       kdamond.0  8282 [007]   664.187237: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 597266432-900239360: 0 140** **       kdamond.0  8282 [007]   664.187237: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 900239360-980148224: 0 140*        kdamond.0  8282 [007]   664.187238: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281471544459264-281471789129728: 0 1        kdamond.0  8282 [007]   664.187238: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281471789129728-281472066732032: 0 0        kdamond.0  8282 [007]   664.187238: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472066732032-281472281972736: 0 1        kdamond.0  8282 [007]   664.187239: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472281972736-281472346124288: 1 0        kdamond.0  8282 [007]   664.187239: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472346124288-281472379187200: 0 1        kdamond.0  8282 [007]   664.187239: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472379187200-281472678154240: 1 0        kdamond.0  8282 [007]   664.187239: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472678154240-281472951209984: 1 0        kdamond.0  8282 [007]   664.187240: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472951209984-281473069228032: 2 0        kdamond.0  8282 [007]   664.187240: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281473069228032-281473299972096: 0 1        kdamond.0  8282 [007]   664.187241: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281473299972096-281473603727360: 0 0        kdamond.0  8282 [007]   664.187241: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281473603727360-281473611063296: 0 5        kdamond.0  8282 [007]   664.187242: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281474851557376-281474851692544: 0 140 *       kdamond.0  8282 [007]   664.287642: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 4194304-305254400: 0 141* *       kdamond.0  8282 [007]   664.287643: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 305254400-597266432: 0 141* *       kdamond.0  8282 [007]   664.287643: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 597266432-900239360: 0 141* *       kdamond.0  8282 [007]   664.287650: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 900239360-980148224: 0 141*        kdamond.0  8282 [007]   664.287650: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281471544459264-281471789129728: 0 2        kdamond.0  8282 [007]   664.287651: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281471789129728-281472066732032: 0 1        kdamond.0  8282 [007]   664.287651: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472066732032-281472349429760: 0 0        kdamond.0  8282 [007]   664.287651: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472349429760-281472588464128: 0 0        kdamond.0  8282 [007]   664.287652: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472588464128-281472678154240: 0 0        kdamond.0  8282 [007]   664.287652: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472678154240-281472951209984: 0 0        kdamond.0  8282 [007]   664.287652: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281472951209984-281473092300800: 1 0        kdamond.0  8282 [007]   664.287653: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281473092300800-281473299972096: 0 2        kdamond.0  8282 [007]   664.287654: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281473299972096-281473421471744: 0 1        kdamond.0  8282 [007]   664.287654: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281473421471744-281473603727360: 2 0        kdamond.0  8282 [007]   664.287654: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281473603727360-281473611063296: 0 6        kdamond.0  8282 [007]   664.287655: damon:damon_aggregated: target_id=18446462650354140800 nr_regions=16 281474851557376-281474851692544: 0 141 > > > Thanks, > SJ > >> Signed-off-by: Xin Hao >> --- >> include/trace/events/damon.h | 7 +++++-- >> 1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/include/trace/events/damon.h b/include/trace/events/damon.h >> index 2f422f4f1fb9..99ffa601e351 100644 >> --- a/include/trace/events/damon.h >> +++ b/include/trace/events/damon.h >> @@ -22,6 +22,7 @@ TRACE_EVENT(damon_aggregated, >> __field(unsigned long, start) >> __field(unsigned long, end) >> __field(unsigned int, nr_accesses) >> + __field(unsigned int, age) >> ), >> >> TP_fast_assign( >> @@ -30,11 +31,13 @@ TRACE_EVENT(damon_aggregated, >> __entry->start = r->ar.start; >> __entry->end = r->ar.end; >> __entry->nr_accesses = r->nr_accesses; >> + __entry->age = r->age; >> ), >> >> - TP_printk("target_id=%lu nr_regions=%u %lu-%lu: %u", >> + TP_printk("target_id=%lu nr_regions=%u %lu-%lu: %u %u", >> __entry->target_id, __entry->nr_regions, >> - __entry->start, __entry->end, __entry->nr_accesses) >> + __entry->start, __entry->end, >> + __entry->nr_accesses, __entry->age) >> ); >> >> #endif /* _TRACE_DAMON_H */ >> -- >> 2.31.0 -- Best Regards! Xin Hao