Hi Alison, On Thu, Aug 05, 2021 at 01:16:17PM -0700, Alison Chaiken wrote: > The advice in the RT wiki > > https://rt.wiki.kernel.org/index.php/HOWTO:_Build_an_RT-application#Hyper_threading > > about configuring the kernel and building RT applications was written > in 2014, when we were on the 3.x series. That makes one wonder how > relevant some of it is for the 5.x series, especially since processors > in common use have changed some since then. Some of the advice, > notably about power management, obviously is timeless. > > In particular, Daniel Wagner added: > > https://rt.wiki.kernel.org/index.php/HOWTO:_Build_an_RT-application#Hyper_threading > > "Hyper threading and also out of order execution of CPUs introduces > 'random' latencies. As mentioned in power management, it is > recommended to disable these feature (if possible) or carefully > benchmark the performance." > > Is the advice still current? I don't think the situation has changed. Though, I don't run these test on modern hardware on regular basis. The last time I played with it on a bit more modern hardware it was still measurable by cyclictest with hackbench as workload. > Should we RT-users all still turn hyperthreading off? Obviously, it depends on your use case. If your application can tolerate the added noise by SMT, you don't have to disable it. > Given the security vulnerabilities associated > with hyperthreading, there are clearly some use cases where doing so > is indicated anyway. Again it depends on your use case. Daniel
