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: > [...] > > > > Hi SeongJae, > > > > We set 'access_pattern' and 'stat' action in schemes when apps are on > > foreground, record apps' memory access pattern when they are switched > > to the background with 'update_schemes_tried_regions' state. But it > > catch the snapshot after next aggregation interval. DAMON is still > > sampling during the app switches to the background and the next > > aggregation time, which can cause the value of "age" to change. The > > sampling results during this period cannot accurately reflect the app's > > foreground access pattern. > > > > 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. > > > 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? Thanks. > > > > Do you have any other suggestions? > > As I mentioned above, I'd suggest the DAMOS apply interval of single sampling > interval for now. > > > Thanks, > SJ > > > > > Thanks.
