[LSF/MM TOPIC] Proactive Memory Reclaim

[Shakeel Butt <shakeelb@google.com>]

Though this is quite late, I still want to propose a topic for
discussion during LSFMM'19 which I think will be beneficial for Linux
users in general but particularly the data center users running a
range of different workloads and want to reduce the memory cost.

Topic: Proactive Memory Reclaim

Motivation/Problem: Memory overcommit is most commonly used technique
to reduce the cost of memory by large infrastructure owners. However
memory overcommit can adversely impact the performance of latency
sensitive applications by triggering direct memory reclaim. Direct
reclaim is unpredictable and disastrous for latency sensitive
applications.

Solution: Proactively reclaim memory from the system to drastically
reduce the occurrences of direct reclaim. Target cold memory to keep
the refault rate of the applications acceptable (i.e. no impact on the
performance).

Challenges:
1. Tracking cold memory efficiently.
2. Lack of infrastructure to reclaim specific memory.

Details: Existing "Idle Page Tracking" allows tracking cold memory on
a system but it becomes prohibitively expensive as the machine size
grows. Also there is no way from the user space to reclaim a specific
'cold' page. I want to present our implementation of cold memory
tracking and reclaim. The aim is to make it more generally beneficial
to lot more users and upstream it.

More details:
"Software-driven far-memory in warehouse-scale computers", ASPLOS'19.
https://youtu.be/aKddds6jn1s