Towards Less CPU-Intensive PMEM File Systems

  • Conference:

    GI Fachgruppe Betriebssysteme Herbsttreffen 2021

  • Place:

    Trondheim

  • Date:

    September 21-22, 2021

  • Author:

    Lukas Werling, Christian Schwarz, Frank Bellosa

  • Persistent memory (PMEM) such as Intel Optane is a new type of storage medium that is attached directly to the memory bus. It is byte-addressable and has very low access latencies. A common way to consume PMEM is via PMEM-aware file systems. Applications can then use the traditional file system interface or memory-map PMEM into their address space (DAX).

    We observe negative performance implications on the whole system caused by processes accessing file systems on PMEM. Once the PMEM write bandwidth is saturated, common wisdom regarding I/O bound and CPU bound processes does not apply anymore. We argue that this is unacceptable for in-kernel file systems and propose a new interface for implementing PMEM file systems based on copy offloading. By monitoring the PMEM write bandwidth, we can detect overload and switch to off-CPU copying.