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 also investigated the operation schemes you mentioned, but we don't > > > > think it can fit our needs. > > > > > > > > On android, user will open many apps and switch between these apps as > > > > needs. We hope to monitor apps' memory access only when they are on > > > > foreground and record the memory access pattern when they are switched > > > > to the background. > > > > > > > > When avaliable memory reaches a threshold, we will use these access > > > > patterns with some strategies to recognize those memory that will have > > > > little impact on user experience and to reclaim them proactively. > > > > > > > > I'm not sure I have clarified it clearly, if you still have questions > > > > on this, please let us know. > > > > > > So, to my understanding, you expect applications may keep similar access > > > pattern when they are in foreground, but have a different, less aggressive > > > access pattern in background, and therefore reclaim memory based on the > > > foreground-access pattern, right? > > > > > > > Different apps may have different access pattern. On android, the apps will > > join in freeze cgroup and be frozen after switch to the background. So we > > monitor apps' memory access only when they are in foreground. > > Thank you for this enlightening me :) > > > > Very interesting idea, thank you for sharing! > > > > > > Then, yes, I agree current DAMOS might not that helpful for the situation, and > > > this record feature could be useful for your case. > > > > > > That said, do you really need full recording of the monitoring results? If > > > not, DAMOS provides DAMOS tried regions feature[1], which allows users get the > > > monitoring results snapshot that include both frequency and recency of all > > > regions in an efficient way. If single snapshot is not having enough > > > information for you, you could collect multiple snapshots. > > > > > > You mentioned absence of Python on Android as a blocker of DAMOS use on the > > > previous reply[2], but DAMOS tried regions feature is not depend on tracepoints > > > or Python. > > > > > > Of course, I think you might already surveyed it but found some problems. > > > Could you please share that in detail if so? > > > > > DAMOS tried regions feature you mentioned is not fully applicable. It needs to > > apply schemes on regions. There is no available scheme we can use for our use > > case. What we need is to return regions with access frequency and recency to > > userspace for later use. > > > Thank you for the answer, I understand your concern. One of the available > DAMOS action is 'stat'[1], which does nothing but just count the statistic. > Using DAMOS scheme for any access pattern with 'stat' action, you can extract > the access pattern via DAMOS tried regions feature of DAMON sysfs interface, > without making any unnecessary impact to the workload. > > Quote from [2]: > > The expected usage of this directory is investigations of schemes' behaviors, > and query-like efficient data access monitoring results retrievals. For the > latter use case, in particular, users can set the action as stat and set the > access pattern as their interested pattern that they want to query. > > For example, you could > > # cd /sys/kernel/mm/damon/admin > # > # # populate directories > # echo 1 > kdamonds/nr_kdamonds; echo 1 > kdamonds/0/contexts/nr_contexts; > # echo 1 > kdamonds/0/contexts/0/schemes/nr_schemes > # cd kdamonds/0/contexts/0/schemes/0 > # > # # set the access pattern for any case (max as 2**64 - 1), and action as stat > # echo 0 > access_pattern/sz/min > # echo 18446744073709551615 > access_pattern/sz/max > # echo 0 > access_pattern/nr_accesses/min > # echo 18446744073709551615 > access_pattern/nr_accesses/max > # echo 0 > access_pattern/age/min > # echo 18446744073709551615 > access_pattern/age/max > # echo stat > action > > And this is how DAMON user-space tool is getting the snapshot with 'damo show' > command[3]. > > Could this be used for your case? Please ask any question if you have :) > > [1] https://docs.kernel.org/admin-guide/mm/damon/usage.html#schemes-n > [2] https://docs.kernel.org/admin-guide/mm/damon/usage.html#schemes-n-tried-regions, > [3] https://github.com/awslabs/damo/blob/next/USAGE.md#damo-show Thank you for your detailed response, it is very helpful to us. We will look into it and contact you if we have any questions. > > > Thanks, > SJ > > > > [1] https://docs.kernel.org/admin-guide/mm/damon/usage.html#schemes-n-tried-regions > > > [2] https://lore.kernel.org/damon/20231129131315.GB12957@cuiyangpei/ > > > > > > > > > Thanks, > > > SJ > > > > > > > > > > > Thanks.
