On 3/6/25 16:45, Bharata B Rao wrote: > Hi, > > This is an attempt towards having a single subsystem that accumulates > hot page information from lower memory tiers and does hot page > promotion. > > At the heart of this subsystem is a kernel daemon named kpromoted that > does the following: > > 1. Exposes an API that other subsystems which detect/generate memory > access information can use to inform the daemon about memory > accesses from lower memory tiers. > 2. Maintains the list of hot pages and attempts to promote them to > toptiers. > > Currently I have added AMD IBS driver as one source that provides > page access information as an example. This driver feeds info to > kpromoted in this RFC patchset. More sources were discussed in a > similar context here at [1]. > Is hot page promotion mandated or good to have? Memory tiers today are a function of latency and bandwidth, specifically in mt_aperf_to_distance() adist ~ k * R(B)/R(L) where R(x) is relatively performance of the memory w.r.t DRAM. Do we want hot pages in the top tier all the time? Are we optimizing for bandwidth or latency? > This is just an early attempt to check what it takes to maintain > a single source of page hotness info and also separate hot page > detection mechanisms from the promotion mechanism. There are too > many open ends right now and I have listed a few of them below. > <snip> > This is just an early RFC posted now to ignite some discussion > in the context of LSFMM [2]. > I look forward to any summary of the discussions Balbir Singh
