Messages in this thread | | | Date | Mon, 7 Oct 2019 10:08:47 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 3/3] x86/ftrace: Use text_poke() |
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On Fri, Oct 04, 2019 at 10:10:47AM +0200, Daniel Bristot de Oliveira wrote: > 1) the enabling/disabling ftrace path > 2) the int3 path - if a thread/irq is running a kernel function > 3) the IPI - that affects all CPUs, even those that are not "hitting" trace > code, e.g., user-space. > > The first one is for sure a cold-path. The second one is a hot-path: any task > running kernel functions will hit it. But IMHO, the hottest one is the IPIs, > because it will run on all CPUs, e.g., even isolated CPUs that are running in > user-space.
Well, we can fix that, just like RCU. In fact, I suspect RCU has all the bits required to cure this.
For NOHZ_FULL CPUs you can forgo the IPI and delay it until the next kernel entry, just like RCU.
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