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RADV Vulkan Driver Adds Option To Force Smart Access Memory Behavior

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  • RADV Vulkan Driver Adds Option To Force Smart Access Memory Behavior

    Phoronix: RADV Vulkan Driver Adds Option To Force Smart Access Memory Behavior

    The latest "Smart Access Memory" work by the open-source AMD Radeon graphics driver stack is an option for the RADV Vulkan driver to force the "SAM" behavior even if the system is not advertising all the video RAM as visible or even if using APU graphics...

    http://www.phoronix.com/scan.php?pag...tion-Force-SAM

  • #2
    Is this AMD CPU+GPU or can it be Intel CPU + AMD GPU? It would be a massive feature if it was allowable by both

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    • #3
      I suppose he meant: "So that people with large BAR can try this out."

      I haven't noticed an impact in Company of Heroes 2 though which is the only game I tested it with (via Proton 5.0-10). As my Haswell/Vega 56-system should be capable of large BAR (according to dmesg it shows the full VRAM), it should force the driver to enable SAM, right?
      Last edited by ms178; 02 March 2021, 07:19 AM.

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      • #4
        Oh my, all those options really get confusing and I don't know of a place where that info is collected and kept up to date. Probably that's the reason why so many people want a GUI for managing this stuff.

        So, if I get this correctly: on RADV SAM is always enabled if one got resizable bar support in the bios, even for configurations other than the AMD advertised Zen 5000 series combined with a Radeon RX 6000 series. But this now enables it even if the bios doesn't advertise resizable bar support?
        And on radeonsi we still only get SAM with Zen 5000 / Radeon RX 6000 by default but have to enable it for other combinations with some env var?

        Sheesh, and in a few months it's probably all different again

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        • #5
          Originally posted by ms178 View Post
          I suppose he meant: "So that people with large BAR can try this out."
          No, it's for 'without' as noted in the article it skips the other checks.
          Michael Larabel
          http://www.michaellarabel.com/

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          • #6
            so presumably this won't make any difference to anyone who already has resizable BAR?

            When AMD first introduced "smart memory access" I did some crude tests with it on and off, I never noticed any difference in games with a 256mb BAR and a 16gb BAR. Should this actually offer much in the way of performance for most people?

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            • #7
              Originally posted by mazumoto View Post
              Oh my, all those options really get confusing and I don't know of a place where that info is collected and kept up to date. Probably that's the reason why so many people want a GUI for managing this stuff.

              So, if I get this correctly: on RADV SAM is always enabled if one got resizable bar support in the bios, even for configurations other than the AMD advertised Zen 5000 series combined with a Radeon RX 6000 series. But this now enables it even if the bios doesn't advertise resizable bar support?
              And on radeonsi we still only get SAM with Zen 5000 / Radeon RX 6000 by default but have to enable it for other combinations with some env var?

              Sheesh, and in a few months it's probably all different again
              That's why I'd like a GUI. It can be a motherf*cker keeping up with AMD driver developments; especially if a person isn't an avid Phoronix reader.

              bridgman AMD should hire Michael for all the work he does keeping the open source community informed of all their changes.

              I have all this enabled in my BIOS . Unfortunately, my motherboard is all that's compatible . By the numbers my R5 4650g is 350 shy of 5000 and my RX 580 is clearly off by a factor of 10 plus 200 .

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              • #8
                Originally posted by Michael View Post

                No, it's for 'without' as noted in the article it skips the other checks.
                Actually it is ambiguous. While the RADV option is very broad and lets you run SAM on unsupported systems, why would someone do this if their system doesn't support it? But there are systems like Haswell which are supporting "large BAR" in general, also Vega 56 should support it, too - at least dmesg shows full VRAM for BAR when having "Above 4G decoding" enabled, but such systems are currently missing out on RadeonSI on that feature unless using the "radeonsi_enable_sam=true" variable. I thought this new RADV option talked about here to be an equivalent to this RadeonSI environment variable. But then it would only make sense for people like me to use it to enjoy the benefits on capable but untested / not-officially whitlisted hardware combinations. But not for people who lack such hardware support in the first place. But then I would clear that up in the comment.
                Last edited by ms178; 02 March 2021, 11:30 AM.

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                • #9
                  So what are the requirements for this? Also, how would I combine this with RADV_PERFTEST=aco ?

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                  • #10
                    Originally posted by mazumoto View Post
                    Oh my, all those options really get confusing and I don't know of a place where that info is collected and kept up to date. Probably that's the reason why so many people want a GUI for managing this stuff.
                    Yes, that's one of the main reasons I want a GUI for AMD GPUs!

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