Speaker
Description
On a densely shared host, a routine event breaks tenant isolation: a task holding a shared kernel lock (filesystem metadata, a control-plane mutex/rwsem) allocates inside the critical section, the allocation falls into memory reclaim, and until reclaim finishes every other task waiting on that lock — from any cgroup — pays the stall. Shared kernel locks aren't mediated by cgroups or memcg limits, so this is cross-tenant priority inversion, and overcommit makes it worse.
In this talk we will present the data we have gathered across the Meta fleet on this problem, and share how we think the solution should take shape. Rather than a finished design or patch series, the goal is to lay out the problem space, the constraints any fix must satisfy, our current direction, and the open questions and to get early feedback from the upstream community.