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VM Performance Showing Mixed Impact With Linux 4.15 KPTI Patches

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  • VM Performance Showing Mixed Impact With Linux 4.15 KPTI Patches

    Phoronix: VM Performance Showing Mixed Results With Linux 4.15 KPTI Patches

    Continuing on with our Linux Kernel Page Table Isolation (KPTI) performance testing are some benchmark results when running tests within a virtual machine on Xeon class hardware.

    http://www.phoronix.com/vr.php?view=25779

  • #2
    Your testbed has slow SSD.
    Please Intel SSD 900p or Samsung 960PRO instead.

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    • #3
      Since Meltdown effectively affect every Intel's processor since 1995 (except Intel Itanium and Intel Atom before 2013)... then any test of any of all these is gut

      And logo is cool, but where is wallapper



      https://en.wikipedia.org/wiki/Meltdo...lnerability%29
      Last edited by dungeon; 01-04-2018, 12:36 AM.

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      • #4
        Originally posted by dungeon View Post
        Since Meltdown effectively affect every Intel's processor since 1995 (except Intel Itanium and Intel Atom before 2013)... then any test of any of all these is gut

        And logo is cool, but where is wallapper



        https://en.wikipedia.org/wiki/Meltdo...lnerability%29
        Originally posted by dungeon View Post
        Since Meltdown effectively affect every Intel's processor since 1995 (except Intel Itanium and Intel Atom before 2013)... then any test of any of all these is gut

        And logo is cool, but where is wallapper



        https://en.wikipedia.org/wiki/Meltdo...lnerability%29
        @Michael: you are honored @wiki
        Patches[edit]

        Microsoft released an emergency update to Windows 10 to address the vulnerability on January 3rd, 2018,[9]and is expected to release the patches to other supported versions of Windows in an upcoming Patch Tuesday.[10]Linux kernel developers have a set of patches named kernel page-table isolation (KPTI) to be released in kernel 4.15 in early 2018, which has been released as a backport in kernel 4.14.11.[11][12]macOS has been patched since 10.13.2.[10] In some cases, the fixes would make the computers equipped with those CPUs 30% slower.[1]Phoronix reported no effect on Linux gaming performance.[3]

        Good job!

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        • #5
          Exploit is out:

          https://twitter.com/brainsmoke/statu...3A%2F%2Fwww.th eregister.co.uk%2F2018%2F01%2F02%2Fintel_cpu_desig n_flaw%2F

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          • #6
            Originally posted by nuetzel View Post
            Exploit is out:

            https://twitter.com/brainsmoke/statu...3A%2F%2Fwww.th eregister.co.uk%2F2018%2F01%2F02%2Fintel_cpu_desig n_flaw%2F
            DELET this!

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            • #7
              Benchmarks with Ryzen/Threadripper at full speed and intels with the slowdown patch would be interesting for many AMD stock holders.

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              • #8
                Originally posted by caligula View Post
                Benchmarks with Ryzen/Threadripper at full speed and intels with the slowdown patch would be interesting for many AMD stock holders.
                AMD is not affected by Meltdown but it is affected by Spectre, so don't jump on that bandwagon too quickly because AMD is going to ultimately get slowed down similarly to Intel when/if an answer to Spectre is coded.

                It's possible that there is no way to protect against Spectre other than disabling branch prediction / speculative execution in the microcode (by inserting codes which force pipeline flushes), in which case both Intel and AMD's Xeon/Threadripper will be dropping to the speed of Atoms clock for clock. :-(

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                • #9
                  Originally posted by linuxgeex View Post

                  AMD is not affected by Meltdown but it is affected by Spectre, so don't jump on that bandwagon too quickly because AMD is going to ultimately get slowed down similarly to Intel when/if an answer to Spectre is coded.

                  It's possible that there is no way to protect against Spectre other than disabling branch prediction / speculative execution in the microcode (by inserting codes which force pipeline flushes), in which case both Intel and AMD's Xeon/Threadripper will be dropping to the speed of Atoms clock for clock. :-(
                  Dude, nobody is going to disable branch prediction and speculative execution on modern high performance CPUs. The patch I'm talking about mitigates Meltdown so it's 100% relevant to compare unpatched AMD vs patched Intel in the future, starting with kernel 4.15.

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                  • #10
                    One easy way to summarize the benchmark results is that, in contrast to some sources on the internet, the KPTI patches will not result in a general slowdown of your computer. They "only" influence the performance of system calls, so software that are affected are those that make a lot of API calls into the kernel. Good examples are server applications that often send small amounts of data over the network (like redis), or more generically, software that communicate with hardware very often in short intervals to the point of making the app almost CPU-bound. This is why these patches hurt cloud service providers, because they live from network performance and hardware virtualization, and so they happen to be affected the most.

                    On the other hand, many end users or even professionals who think now their video compression or rendering/raytracing app will slow down won't be affected almost at all, since these apps are computationally expensive but do 99% of their work without calling into the kernel, hence will not be slowed down. For daily use like browsing, Word, or music, you won't notice a difference either because these didn't hog down your computer anyway, so you have more than enough reserves.

                    I speculate, among individuals probably only gamers are really affected, not meaning that is unimportant (it is a large user base after all), just saying.

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