On Thu, Nov 03, 2022 at 12:05:06PM +0900, Sergey Senozhatsky wrote: < snip > > > Just open question(I might be too paranoid?) > > > > I am thinking someone want to add third comp algorithm in future > > to balance decompression and memory efficiency. > > > > If it's not too crazy idea, let's think about the interface. > > Maybe, could we make the recomp knobs works like list? > > > > # A primary comp > > echo "A" > /zram/comp_algo > > > > # Multiple secondary comps > > echo "B threshold" > /zram/add_recomp_algo > > echo "C threshold" > /zram/add_recomp_algo > > echo "D threshold" > /zram/add_recomp_algo > > What is the threshold here? My design approach is that ZRAM doesn't do As your term, watermark but yeah, priority you suggested would be good for me. > recompression on its own, so no magic is happening automatically. It's > the user-space that triggers recompression for selected pages when > user-space thinks it's time to. This allows us to have various flexible > policies and consider things that ZRAM is not even aware of: battery level, > free memory, CPU load average, etc. E.g. no recompression when all CPUs > are busy rendering video game, or when we are draining battery too fast, > etc. > > > "cat /zram/recomp_algo" shows the list > > > > echo "C" > /zram/remove_recomp_algo > > will remove the C algorithm in stack. > > What is the use case for removal of a secondary algorithm? Without the interface, How can we modify the selection if admin want to change the order of second algorithms? > > > My point is that we don't need to implement it atm but makes the > > interface to open the possibility for future extension. > > > > What do you think? > > So, as far as I understand, we don't have reason to add remove_recomp_algo > right now. And existing recomp_algo does not enforce any particular format, > it can be extended. Right now we accept "$name" but can do something like > "$name:$priority". The only thing that we probably need to do is rename > recomp_algo to either add_recomp_algo or register_recomp_algo? Yeah, I like the name and priority format. Only question is how we could support algorithm selection change under considering multiple secondary algorithms.
