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Looking At The Linux Performance Two Years After Spectre / Meltdown Mitigations

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  • #11
    Guys, Intel did not fix these defects by fixing the hardware design. That would have required a major redesign.
    Low-hanging fruits could have been fixed in actual hardware but the rest is just the same broken CPUs shipped with "fixes" (workarounds) in the firmware.

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    • #12
      still no tests with all mitigations enabled (rather than just the default ones)?

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      • #13
        Great testing. Does show how badly ignorant we've been to hw cheating.

        I'd like to see how AMD has faired here, with Zen1-3 and EPYC + TR chips.

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        • #14
          Originally posted by Spam View Post
          Great testing. Does show how badly ignorant we've been to hw cheating.

          I'd like to see how AMD has faired here, with Zen1-3 and EPYC + TR chips.
          No need : it's been done already, on Phoronix, here : https://www.phoronix.com/scan.php?pa...-spectre&num=1

          Zen 1 is almost identical here to Zen+, which included some optimizations in RAM access and cache latency, but absolutely no core redesign. All in all, Ryzen chips weren't impacted much on average.

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          • #15
            Originally posted by slacka View Post
            NoScript + "mitigations=off" for the Win. Don't run untrusted software? No need to lose all your performance.
            1. Too many websites are unusable without JS, even the phoronix forums.
            2. When you don't enable JS, even a PC from 20 years ago is fast enough to browse the web.

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            • #16
              Should have thrown some AMD CPUs in there just to set everyone off.

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              • #17
                Originally posted by johannesburgel View Post
                Honestly, Michael: This kind of content should only be available to paying subscribers for the first week after publication.
                Are you trying to turn this into LWN?

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                • #18
                  And this was tested against 5.4 kernel. Didn't I read that some better mitigation work went into 5.5 (which is what 20.04 will be using) which should lessen the mitigations=on perf hit a bit more? This test re-run once 5.5 lands would give a clearer picture I'd think.

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                  • #19
                    Originally posted by kozman View Post
                    And this was tested against 5.4 kernel. Didn't I read that some better mitigation work went into 5.5 (which is what 20.04 will be using) which should close the mitigations=on per gap a bit more? This test re-run once 5.5 lands would give a clearer picture I'd think.
                    Can't think of any mitigation improvement in 5.5.
                    Michael Larabel
                    http://www.michaellarabel.com/

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                    • #20
                      Originally posted by slacka View Post
                      NoScript + "mitigations=off" for the Win. Don't run untrusted software? No need to lose all your performance.
                      AMD disable the microcode.

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