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Fresh Linux 4.16 Kernel Benchmarks With KPTI & Retpolines

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  • #11
    Originally posted by dungeon View Post

    Yep, only benchmark uses that and no one else, so it represents - nothing
    ...

    It represents the status before spectre and meltdown got discovered. What's wrong with that? What people want to know is how hard the performance impact is and that's how you're going to measure it: 4.16 has all the fixes while 4.14.0 has none.
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    • #12
      Originally posted by darkbasic View Post
      It represents the status before spectre and meltdown got discovered. What's wrong with that?
      Wrong is that people will make wrong conclusion "how 4.14 is better than something else" aka immediately first comment by PLum get this way

      While point should be "how much performice-wise mitigation patches affects same kernel version" and this article does not answering that, so conclusion is nowhere - as article mostly talks about some it seems unrelated regression
      Last edited by dungeon; 03-05-2018, 02:11 PM.

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      • #13
        Linux has some serious regressions since 4.15! Hope they fix it!

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        • #14
          Originally posted by dungeon View Post

          Wrong is that people will make wrong conclusion "how 4.14 is better than something else" aka immediately first comment by PLum get this way

          While point should be "how much performice-wise mitigation patches affects same kernel version" and this article does not answering that, so conclusion is nowhere - as article mostly talks about some it seems unrelated regression
          I think that it is not possible to completely disable mitigation patches for all attack variants, otherwise Michael would have done it.
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          Intel: GMA45, HD3000 (Core i5 2500K)

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          • #15
            Some of the spectre patches seem to be permanent. This will be a problem if they are mitigated in hardware and the expected performance doesn't return.

            It seems odd Gimp performance went down, I wouldn't have expected that.

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            • #16
              Originally posted by toyotabedzrock View Post
              This will be a problem if they are mitigated in hardware
              Not to worry.

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              • #17
                Originally posted by ryszardzonk View Post
                I wonder if kernel 4.14.0 performance equals that of 4.14.24. After all those repotoline/ktpi patches have been backported to the 4.14 branch.
                I have compared an up-to-date 4.14 (4.14.23-1-lts on Arch) to a few versions of 4.15 and 4.14 always comes out ahead, sometimes significantly so. and according to PTS, that is with "KPTI + __user pointer sanitization + Full generic retpoline Protection".

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                • #18
                  how do you disable them?

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                  • #19
                    Originally posted by darkbasic View Post
                    I think that it is not possible to completely disable mitigation patches for all attack variants, otherwise Michael would have done it.
                    Well, we shouldn't promote disabling of anything as in reality most people won't disable anything and just run default . That is why i think most people are interested to see "before & now" default comparison like this:

                    https://www.phoronix.com/forums/foru...28#post1011228

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                    • #20
                      Originally posted by dungeon View Post

                      Well, we shouldn't promote disabling of anything as in reality most people won't disable anything and just run default . That is why i think most people are interested to see "before & now" default comparison like this:

                      https://www.phoronix.com/forums/foru...28#post1011228
                      Backports don't contain ALL mitigation patches yet, so if you want to know the cumulative impact of ALL mitigation patches you still need to disable everything on top of latest development kernel. The alternative is to benchmark 4.14.0 against 4.16-rc like Michael did, but that means you can possibly hit other regressions as well.
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                      AMD: X1950XTX, HD3870, HD5870
                      Intel: GMA45, HD3000 (Core i5 2500K)

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