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Message-ID: <5089fd16-bc8c-4231-a89b-2658445e04b7@csgroup.eu> Date: Wed, 27 Nov 2024 07:44:00 +0100 From: Christophe Leroy <christophe.leroy@...roup.eu> To: Shrikanth Hegde <sshegde@...ux.ibm.com>, mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org Cc: npiggin@...il.com, maddy@...ux.ibm.com, bigeasy@...utronix.de, ankur.a.arora@...cle.com, linux-kernel@...r.kernel.org, mark.rutland@....com, vschneid@...hat.com, peterz@...radead.org Subject: Re: [PATCH 2/3] powerpc: support dynamic preemption Le 25/11/2024 à 05:22, Shrikanth Hegde a écrit : > Once the lazy preemption is supported, it would be desirable to change > the preemption models at runtime. So this change adds support for dynamic > preemption using DYNAMIC_KEY. > > In irq-exit to kernel path, use preempt_model_preemptible for decision. > Other way would be using static key based decision. Keeping it > simpler since key based change didn't show performance improvement. What about static_call, wouldn't it improve performance ? > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 6d6bbd93abab..01c58f5258c9 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -270,6 +270,7 @@ config PPC > select HAVE_PERF_EVENTS_NMI if PPC64 > select HAVE_PERF_REGS > select HAVE_PERF_USER_STACK_DUMP > + select HAVE_PREEMPT_DYNAMIC_KEY Can you use HAVE_PREEPT_DYNAMIC_CALL instead ? That should be more performant. I know static calls are not in for PPC64 yet, you can restart from http://patchwork.ozlabs.org/project/linuxppc-dev/cover/20221010002957.128276-1-bgray@linux.ibm.com/ and https://github.com/linuxppc/issues/issues/416 Christophe
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