Back in 2020, Resizable BAR was all the rage with AMD and NVIDIA enabling support for the feature on their graphics cards, but now Intel has also confirmed adding support for the technology on their upcoming Arc Alchemist GPUs.
Intel Arc Alchemist GPUs will get resizable bar support on Linux
In a report by Phoronix, the latest Linux graphics kernel mentioned support for ‘Resizable BAR’ or ReBAR in patches. The latest fixes include small BAR recovery support for Intel’s Kernel graphics driver on the Linuxx platform. Here is what the patch says:
Starting with DG2 we will have resizable BAR support for device local memory, but in some cases the final BAR size may still be less than the total local memory size. In such cases, only part of the local memory will be accessible to the CPU, while the rest is only accessible through the GPU. This series adds the basic enablers necessary to ensure that the entire local memory range is usable.
Since the patch was sent for Linux 5.17, it’s likely that we could see Resizable BAR support added as early as Linux 5.18. So, if users don’t want to use ReBAR with Intel’s GPUs within the Linux ecosystem, they will need to upgrade to the latest Linux and MESA release. Intel already offers Resizable BAR support on its desktop platforms starting with the 300-series lineup and since other GPU manufacturers are offering the technology on desktops and laptops, it Intel is also likely to follow the same path with its Arc Alchemist line of GPUs.
ReBAR essentially defines the amount of discrete GPU memory space that can be mapped, and PCs today are typically limited to 256MB of mapped memory. With BAR, the system can access all GPU memory, removing any bottlenecks to enable faster performance. So far, BAR has shown mixed performance with gains in some titles and no performance advantage in others. There are also a few instances where the system produces lower performance with BAR enabled, but that’s only a small part, so enabling it isn’t a bad idea and it’s great to see Intel also working on making these open source features.