Messages in this thread | | | From | Xin Hao <> | Subject | Re: [PATCH V1 2/2] mm/damon: Add 'age' of region tracepoint support | Date | Thu, 11 Nov 2021 16:29:23 +0800 |
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Hi, Park:
On 2021/11/11 下午4:20, SeongJae Park wrote: > On Thu, 11 Nov 2021 10:04:38 +0800 Xin Hao <xhao@linux.alibaba.com> wrote: > >> [-- Attachment #1: Type: text/plain, Size: 8070 bytes --] >> >> Hi Park: >> >> On 2021/11/10 下午9:16, SeongJae Park wrote: >>> On Wed, 10 Nov 2021 20:13:14 +0800 Xin Hao <xhao@linux.alibaba.com> 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. > I understand that you don't want to record all the traces and then process the > huge trace data in user space in order to get the age information, because you > want to save disk space and CPU cycles. Is that correct? If so, I think that > makes sense, and it would be better to put that in the commit message.
Yes, What you said is absolutely correct, that's how I thought about it, I will add this part of the
information to the commit,thanks!
> > > Thanks, > SJ > > [...]
-- Best Regards! Xin Hao
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