Hello Matthias,
For GCC, you need 7.3.0 or later. For Microsoft you need VS2017 and I
think some minimal update version (the option is called -Qspectre), we
use 15.5.5.
I was not involved in the benchmarking so I don't know any details
there, only the conclusion.
/Erik
On 2018-06-05 01:30, Baesken, Matthias wrote:
Hi Erik , is there some info available about the performance impact
when disabling disabling speculative execution ?
And which compiler versions are needed for this ?
Best regards, Matthias
>We need to add compilation flags for disabling speculative execution to
>our native libraries and executables. In order to allow for users not
>affected by problems with speculative execution to run a JVM at full
>speed, we need to be able to ship two JVM libraries - one that is
>compiled with speculative execution enabled, and one that is compiled
>without. Note that this applies to the build time C++ flags, not the
>compiler in the JVM itself. Luckily adding these flags to the rest of
>the native libraries did not have a significant performance impact so
>there is no need for making it optional there.
>
>This patch defines flags for disabling speculative execution for GCC and
>Visual Studio and applies them to all binaries except libjvm when
>available in the compiler. It defines a new jvm feature
>no-speculative-cti, which is used to control whether to use the flags
>for libjvm. It also defines a new jvm variant "altserver" which is the
>same as server, but with this new feature added.
>
>For Oracle builds, we are changing the default for linux-x64 and
>windows-x64 to build both server and altserver, giving the choice to the
>user which JVM they want to use. If others would prefer this default, we
>could make it default in configure as well.
>
>The change in GensrcJFR.gmk fixes a newly introduced race that appears
>when building multiple jvm variants.
>
>Bug: https://bugs.openjdk.java.net/browse/JDK-8202384
>
>Webrev: http://cr.openjdk.java.net/~erikj/8202384/webrev.01
<http://cr.openjdk.java.net/%7Eerikj/8202384/webrev.01>
