On Wed, 10 Nov 2021 20:13:14 +0800 Xin Hao <xhao@xxxxxxxxxxxxxxxxx> 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?
Thanks,
SJ
>
> Signed-off-by: Xin Hao <xhao@xxxxxxxxxxxxxxxxx>
> ---
> 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
