Yet another pull request sent in early ahead of the holidays for the Linux 4.21 kernel merge window are the DMA-Mapping updates managed by Christoph Hellwig. Normally the DMA-Mapping changes aren’t really worth noting on Phoronix, but this time around it brings some improvements to help offset the overhead incurred by Retpolines for Spectre V2 mitigation…

Source: Phoronix – Linux DMA Mapping Updates Help Recover Losses Caused By Spectre V2 Retpolines