Software-defined far memory in warehouse scale computers

With T set at 120 seconds, 32% of the memory usage in a Google WSC is cold on average. zswap’s default control plane did not meet Googles strict performance slowdown and CPU overhead budgets though, so they built a new one to identify cold pages and proactively migrate them to far memory while treating performance as a first-class constraint. This enabled Google to convert zswap’s cold memory coverage into lower memory provisioning, achieving a 4-5% reduction in DRAM CTO.

Source: blog.acolyer.org