OpenRISC Sees Sane TLB Flushing With Linux 5.9
Written by Michael Larabel in Hardware on 15 August 2020 at 12:02 AM EDT. Add A Comment
HARDWARE --
While RISC-V is flourishing when it comes to this open-source CPU architecture, the related OpenRISC architecture is still advancing but not seeing as much hardware efforts around it. In any case, the Linux kernel support continues improving for OpenRISC and with Linux 5.9 are more improvements.

OpenRISC still lacks any open-source ASIC with predominantly being used on FPGAs and a few commercial efforts based on the OpenRISC 1000 architecture. OpenRISC on the Linux software side has continued seeing improvements since its introduction back in 3.1.

For the OpenRISC updates coming now in Linux 5.9 there are various fixes in its architecture code while the closest addition to a feature is an improvement around TLB flushing. Currently when flushing pages from the translation lookaside buffer on SMP OpenRISC, the entire TLB was being flushed for all CPUs. With Linux 5.9, there is support for flushing specific ranges and pages of the TLB to no longer resort to flushing the entire thing. This more selective flushing for the TLB is beneficial for performance.

This and the other OpenRISC work included for Linux 5.9 can be found via this pull request.

On the RISC-V front, sent out on Friday was a new patch series worth noting. These patches (not for Linux 5.9) unify the NUMA implementation between ARM64 and RISC-V. The RISC-V developers are looking to leverage the existing 64-bit ARM NUMA code to avoid rewriting a similar implementation.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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