Hello Minchan, On (05/26/16 09:32), Minchan Kim wrote: [..] > Unfortunately, I don't have now. However, I don't feel we need a data for > that because *unbounded work* within VM interaction context is bad. ;-) fair enough, even though the shrinker doesn't put any constraints here. > > hm, probably it makes sense to change it. but if the change will > > replace "1 full pool scan" to "2 scans of 1/2 of pool's classes", > > then I'm less sure. > > Other shrinker is on same page. They have *cache* which is helpful for > performance but if it's not hot, it can lose performance if memory > pressure is severe. For the balance, comprimise approach is shrinker. > > We can see fragement space in zspage as wasted memory which is bad > on the other hand we can see it as cache to store upcoming compressed > page. So, too much freeing can hurt the performance so, let's obey > VM's rule. If memory pressure goes severe, they want to reclaim more > pages with proportional of memory pressure. I agree that the unused memory has a dual nature here. we don't really do the "compact too much" thing, in a sense that we very rarely compact classes to be ZS_FULL. ~2-3% of the cases (if I recall the testing results correctly). but reducing the class ->lock pressure is a nice thing on its own. so yeah, let's do it! btw, I've uploaded zram-fio test script to https://github.com/sergey-senozhatsky/zram-perf-test it's very minimalistic and half baked, but can be used to some degree. open to patches, improvements, etc. -ss -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>