On Fri, Apr 1, 2022 at 3:26 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > On Thu, Mar 31, 2022 at 4:35 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > On Thu 31-03-22 19:18:58, Zhaoyang Huang wrote: > > > On Thu, Mar 31, 2022 at 5:01 PM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > > > > > On Thu 31-03-22 16:00:56, zhaoyang.huang wrote: > > > > > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > > > > > > > > > > For some kind of memcg, the usage is varies greatly from scenarios. Such as > > > > > multimedia app could have the usage range from 50MB to 500MB, which generated > > > > > by loading an special algorithm into its virtual address space and make it hard > > > > > to protect the expanded usage without userspace's interaction. > > > > > > > > Do I get it correctly that the concern you have is that you do not know > > > > how much memory your workload will need because that depends on some > > > > parameters? > > > right. such as a camera APP will expand the usage from 50MB to 500MB > > > because of launching a special function(face beauty etc need special > > > algorithm) > > > > > > > > > Furthermore, fixed > > > > > memory.low is a little bit against its role of soft protection as it will response > > > > > any system's memory pressure in same way. > > > > > > > > Could you be more specific about this as well? > > > As the camera case above, if we set memory.low as 200MB to keep the > > > APP run smoothly, the system will experience high memory pressure when > > > another high load APP launched simultaneously. I would like to have > > > camera be reclaimed under this scenario. > > > > OK, so you effectivelly want to keep the memory protection when there is > > a "normal" memory pressure but want to relax the protection on other > > high memory utilization situations? > > > > How do you exactly tell a difference between a steady memory pressure > > (say stream IO on the page cache) from "high load APP launched"? Should > > you reduce the protection on the stram IO situation as well? > > IIUC what you are implementing here is a "memory allowance boost" > feature and it seems you are implementing it entirely inside the > kernel, while only userspace knows when to apply this boost (say at > app launch time). This does not make sense to me. I am wondering if it could be more helpful to apply this patch on the background services(system_server etc) than APP, while the latter ones are persistent to the system. > > > > > [...] > > > > One very important thing that I am missing here is the overall objective of this > > > > tuning. From the above it seems that you want to (ab)use memory->low to > > > > protect some portion of the charged memory and that the protection > > > > shrinks over time depending on the the global PSI metrict and time. > > > > But why this is a good thing? > > > 'Good' means it meets my original goal of keeping the usage during a > > > period of time and responding to the system's memory pressure. For an > > > android like system, memory is almost forever being in a tight status > > > no matter how many RAM it has. What we need from memcg is more than > > > control and grouping, we need it to be more responsive to the system's > > > load and could sacrifice its usage under certain criteria. > > > > Why existing tools/APIs are insufficient for that? You can watch for > > both global and memcg memory pressure including PSI metrics and update > > limits dynamically. Why is it necessary to put such a logic into the > > kernel? > > I had exactly the same thought while reading through this. > In Android you would probably need to implement a userspace service > which would temporarily relax the memcg limits when required, monitor > PSI levels and adjust the limits accordingly. As my response to Michal's comment. Userspace monitors introduce latency. Take LMKD as an example, it is actually driven by the PSI_POLL_PERIOD_XXX_MS after first wakeup, which means PSI_WINDOW_SIZE_MS could be too big to rely on. IMHO, with regards to the responding time, LMKD is less efficient than lmk driver but more strong in strategy things. I would like to test this patch in real android's work load and feedback in next version. > > > > > -- > > Michal Hocko > > SUSE Labs
