Interest: P2P DMA doesn't sound like much, but it is...

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catweazel
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Interest: P2P DMA doesn't sound like much, but it is...

Post by catweazel » Fri May 24, 2019 1:45 am

P2P DMA, peer to peer direct memory access - Windwoes has had this highly performance enhancing capability for many years. Those coming to Linux from Windwoes may have noticed that copying files in Windwoes has no discernible impact on CPU or RAM utilisation, whereas on linux, large file copies can often result in excessive CPU and RAM usage. Well, not any more. P2P DMA was implemented for Intel CPUs in kernel 4.20, and now for AMD Zen CPUs in kernel 5.2.

https://www.phoronix.com/scan.php?page= ... en-P2P-DMA
https://www.phoronix.com/scan.php?page= ... ry-Support

P2P DMA allows devices sitting on the PCI bus to communicate directly with each other, without chewing and spewing CPU cycles.

More about P2P DMA: https://lwn.net/Articles/767281/
"There is, ultimately, only one truth -- cogito, ergo sum -- everything else is an assumption." - Me, my swansong.

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nakednorman
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Re: Interest: P2P DMA doesn't sound like much, but it is...

Post by nakednorman » Fri May 24, 2019 6:13 am

Your rig must reach hyper-drive speeds with this :-)
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catweazel
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Re: Interest: P2P DMA doesn't sound like much, but it is...

Post by catweazel » Fri May 24, 2019 6:17 am

nakednorman wrote:
Fri May 24, 2019 6:13 am
Your rig must reach hyper-drive speeds with this :-)
I have to weight it down with concrete blocks because when I turn it on, it levitates. So, yes, I suspect that when I get to adding the new kernel, it might disappear into another dimension :)

That aside, I think this is an exciting development for the kernel.
"There is, ultimately, only one truth -- cogito, ergo sum -- everything else is an assumption." - Me, my swansong.

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