VFIO Gets Batched Page Pinning For An Easy Performance Improvement With Linux 5.12

Written by Michael Larabel in Virtualization on 25 February 2021 at 01:00 PM EST. 1 Comment
The VFIO changes to the Linux 5.12 kernel include an optimization worth mentioning.

The VFIO driver work for Linux 5.12 isn't too significant but the batched page pinning will be of interest to some. Up to now the VFIO kernel code has relied on pinning one 4K page at a time. That major efficiency bottleneck has been addressed with the batched page pinning to handle batches of 512 at a time.

With this optimization pursued by Oracle's Daniel Jordan, he found that QEMU pins pages for guests around 8% faster than on prior kernels.

So with this next version of the Linux kernel the VFIO Type-1 driver should be pinning multiple pages concurrently and in turn should yield faster start times for QEMU guests with 2G+ of memory. That optimization seems to be the main enhancement of the VFIO code for Linux 5.12 besides some fixes and other low-level work.
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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, LinkedIn, or contacted via MichaelLarabel.com.

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