Linux 5.4 To Support NVMe-of P2P Support With Compatible Systems
Written by Michael Larabel in Linux Storage on 24 September 2019 at 06:35 AM EDT. 8 Comments
LINUX STORAGE --
Sent in and already landed on Monday were the PCI changes for Linux 5.4 and includes an interesting feature addition.

With the Linux 5.4 PCI code is support for handling peer-to-peer (P2P) DMA between root ports for whitelisted bridges. This work allows for NVMe over Fabrics (NVMe-of) P2P support to transfer data between devices while bypassing any switching on the root complexes.

The peer-to-peer data transfer performance has the potential obviously for performance/efficiency gains, but it doesn't work nicely on all systems. AMD Zen-based systems though are "lucky" in that they do work well while on the Intel side is a more selective whitelist for compatible bridges. The Intel chipsets with 0x3c00, 0x3c01, 0x2f00, and 0x2f01 are whitelisted in Linux 5.4 for knowing to work well with the P2P requests. Additional hardware will be added when it's been tested and confirmed to work well.

More details from the PCI pull request.
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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 10,000 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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