@misc{RabensteinNguyenGierschetal., author = {Rabenstein, Jonas and Nguyen, Dustin and Giersch, Oliver and Eichler, Christian and H{\"o}nig, Timo and Nolte, J{\"o}rg and Schr{\"o}der-Preikschat, Wolfgang}, title = {Back to the core-memory age: running operating systems in NVRAM only}, series = {Proceedings: architecture of computing systems: 36th International Conference, ARCS 2023, June 13 - 15, 2023}, journal = {Proceedings: architecture of computing systems: 36th International Conference, ARCS 2023, June 13 - 15, 2023}, editor = {Goumas, Georgios and Tomforde, Sven and Brehm, J{\"u}rgen and Wildermann, Stefan and Pionteck, Thilo}, publisher = {Springer-Verlag}, isbn = {978-3-031-42784-8}, doi = {10.1007/978-3-031-42785-5_11}, pages = {153 -- 167}, abstract = {The classic core memory was completely non-volatile and thus kept at least part of the operating system persistently in main memory, even over power cycles. Nowadays we can repeat this approach with NVRAM, but with terabytes of main memory on a completely different scale and with parts of the operating-system state stored in volatile CPU caches. In this paper, we discuss our experiences of running large modern operating systems including their applications entirely in NVRAM. We adapted stock Linux and FreeBSD kernels to work exclusively with NVRAM by hiding all DRAM from the kernels at boot time to establish a realistic performance baseline without changing anything else. Following this entirely NVRAM-agnostic approach, we could observe an effective performance penalty of a factor of about four, but only negligible increases in whole-system power draw. For our system with two CPU sockets and 56 cores total, we also observed a reduction in power draw in several scenarios. Due to prolonged execution times, the energy consumption increased as well for these measured workloads. While this might be discouraging at first sight, this result was achieved without any performance tuning as to the specific characteristics of today's NVRAM technology. Therefore, we are also discussing means to mitigate the observed shortcomings by integrating NVRAM appropriately into the memory hierarchy of future robust persistent systems.}, language = {en} }