On Wed, Jan 09, 2019 at 12:36:11PM -0800, Yang Shi wrote: > As I mentioned above, if we know some page caches from some memcgs > are referenced one-off and unlikely shared, why just keep them > around to increase memory pressure? It's just not clear to me that your scenarios are generic enough to justify adding two interfaces that we have to maintain forever, and that they couldn't be solved with existing mechanisms. Please explain: - Unmapped clean page cache isn't expensive to reclaim, certainly cheaper than the IO involved in new application startup. How could recycling clean cache be a prohibitive part of workload warmup? - Why you cannot temporarily raise the kswapd watermarks right before an important application starts up (your answer was sorta handwavy) - Why you cannot use madvise/fadvise when an application whose cache you won't reuse exits - Why you couldn't set memory.high or memory.max to 0 after the application quits and before you call rmdir on the cgroup Adding a permanent kernel interface is a serious measure. I think you need to make a much better case for it, discuss why other options are not practical, and show that this will be a generally useful thing for cgroup users and not just a niche fix for very specific situations.
