On Mon, Dec 16, 2024 at 07:04:51PM +0100, Petr Tesarik wrote: > Hi all, > > what is the plan for implementing PREEMPT_LAZY on arm64? > > There used to be RT patch series which enabled lazy preemption on > arm64, but this architecture was "sacrificed" in v6.6-rc6-rt10, as > collateral damage of switching to PREEMPT_AUTO. > > IIUC lazy preemption is currently implemented only for architectures > with CONFIG_GENERIC_ENTRY, but there is no inherent dependency on it. > So, is the plan to convert arm64 to GENERIC_ENTRY (and then get > PREEMPT_LAZY for free), or is somebody working on CONFIG_PREEMPT_LAZY > for arm64 without that conversion? I don't think there's an agreed upon plan either way. Jinjie Ruan has been looking to move arm64 over to GENERIC_ENTRY: https://lore.kernel.org/all/20241206101744.4161990-1-ruanjinjie@xxxxxxxxxx/ AFAICT, the only bits that we get "for free" from GENERIC_ENTRY would be the logic in raw_irqentry_exit_cond_resched() and exit_to_user_mode_loop(), and all we'd need to enable this on arm64 as-is would be as below. ... so how important is this? Mark. ---->8----
