On Fri, Jan 26, 2024 at 12:04:54AM -0800, SeongJae Park wrote: > On Fri, 26 Jan 2024 14:57:06 +0800 cuiyangpei <cuiyangpei@xxxxxxxxx> wrote: > > > On Mon, Jan 22, 2024 at 09:56:11AM -0800, SeongJae Park wrote: > > > Hi cuiyangpei, > > > > > > On Mon, 22 Jan 2024 13:46:31 +0800 cuiyangpei <cuiyangpei@xxxxxxxxx> wrote: > > > > > > > On Sun, Dec 03, 2023 at 07:37:45PM +0000, SeongJae Park wrote: > > > > > On 2023-12-03T13:43:13+08:00 cuiyangpei <cuiyangpei@xxxxxxxxx> wrote: > > > > > > > > > > > On Fri, Dec 01, 2023 at 05:31:12PM +0000, SeongJae Park wrote: > > > > > > > Hi Cuiyangpei, > > > > > > > > > > > > > > On Fri, 1 Dec 2023 20:25:07 +0800 cuiyangpei <cuiyangpei@xxxxxxxxx> wrote: > > > > > > > > > > > > > > > On Thu, Nov 30, 2023 at 07:44:20PM +0000, SeongJae Park wrote: > > > > > > > > > Hi Cuiyangpei, > > > > > > > > > > > > > > > > > > On Thu, 30 Nov 2023 17:14:26 +0800 cuiyangpei <cuiyangpei@xxxxxxxxx> wrote: > [...] > > > > Is there any way to catch sampling result immediately after setting the > > > > "update_schemes_tried_regions" state? > > > > > > There is no way for exactly doing this. You would need to proactively collect > > > snapshots while the app is foreground, and use the latest one that collected > > > before the app goes background, like recording-based approach would do. > > > > > > I think recent DAMON changes might make an alternative approach available, > > > though. From v6.7, DAMON provides pseudo-moving-average monitoring result in > > > sampling interval granualrity, since patchset "mm/damon: provide pseudo-moving > > > sum based access rate". And a followup patchset, namely "mm/damon: implement > > > DAMOS apply intervals", has made DAMOS works in the sampling interval > > > granualrity. Both patchsets are merged into v6.7-rc1. > > > > > > Hence, I think you could use 'update_schemes_tried_regions' after you noticed > > > the app's state transition, with DAMOS apply interval of one sampling interval. > > > Then you will get the monitoring results after one sampling interval. Of > > > course, the snapshot may contain some of background access pattern, but > > > wouldn't made it changed significantly, unless you set aggregation interval too > > > short. > > > > All other actions will apply at one sampling interval except for the > > `stat` action. > > > > We use 'update_schemes_tried_regions' after switch to the background. The > > before_damos_apply callback function will only be set when the next aggregation > > interval arrives. The `tried_regions` will only be updated after setting the > > callback function. > > > > DAMON is still sampling during setting 'update_schemes_tried_regions' to the next > > aggregation time, which is not what we expected. The pseudo-moving-average > > monitoring result can reduce nr_accesees inaccuracy, but age is still being modified > > during this time, so it can't improve this issue. > > > > Please let me know if my understanding is incorrect. Thank you. > > So, 'update_schemes_tried_regions' command is firstly handled by > 'damon_sysfs_cmd_request_callback()', which is registered as > after_wmarks_check() and after_aggregation() callback. Hence > 'update_schemes_tried_regions' command is still effectively working in > aggregation interval granularity. I think this is what you found, right? > Yes. > If I'm not wrongly understanding your point, I think the concern is valid. I > think we should make it works in sampling interval granularity. I will try to > make so. Would that work for your use case? > It's much better than working in aggregation interval. I have a question. Why does the 'update_schemes_tried_regions' command need to work in the sampling time or aggregation time? 'update_schemes_tried_regions' is a relatively special state that updates the regions that corresponding operation scheme. Can it be separated from other states and controlled by sysfs node to respond immediately after being written? > > > > > > > Alternatively, can it return the "last_nr_accesses" and "last_age" values in > > > > tried_regions/<N> directory? > > > > > > This could also be a good alternative in my think. Nice idea. But, because > > > the previously mentioned alternative is already available while this require a > > > bit small but additional changes, could we check if the previously one make > > > sense and works first? We could revisit this idea if it turns out the previous > > > alternative is not suffice in my opinion. > > > > > Can you consider adding "last_nr_accesses" and "last_age" two files in > > 'tried_regions/<N>' directory? > > Actually we don't have 'last_age' field, right? And in case of > 'last_nr_accesses', it is a hidden private field, since it is intended to be > accessed by only DAMON core code. Making it exposed to user means exposing > implementation details, and the mechanism that coupled with an exposed > interface is hard to be changed, so be unflexible. Hence I'd prefer making > 'update_schemes_tried_regions' works in sampling interval granularity, more > than exposing the two information if it works for your use case. > Ok, I get it. > Thanks, > SJ > > [...]
