Re: [PATCH v2 2/2] powerpc: Large user copy aware of full:rt:lazy preemption
From: Ankur Arora <hidden>
Date: 2024-11-19 21:09:13
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Shrikanth Hegde [off-list ref] writes:
Large user copy_to/from (more than 16 bytes) uses vmx instructions to speed things up. Once the copy is done, it makes sense to try schedule as soon as possible for preemptible kernels. So do this for preempt=full/lazy and rt kernel.
Note that this check will also fire for PREEMPT_DYNAMIC && preempt=none. So when power supports PREEMPT_DYNAMIC this will need to change to preempt_model_*() based checks.
Not checking for lazy bit here, since it could lead to unnecessary context switches.
Maybe: Not checking for lazy bit here, since we only want to schedule when a context switch is imminently required.
quoted hunk ↗ jump to hunk
Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Shrikanth Hegde <redacted> --- arch/powerpc/lib/vmx-helper.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/arch/powerpc/lib/vmx-helper.c b/arch/powerpc/lib/vmx-helper.c index d491da8d1838..58ed6bd613a6 100644 --- a/arch/powerpc/lib/vmx-helper.c +++ b/arch/powerpc/lib/vmx-helper.c@@ -45,7 +45,7 @@ int exit_vmx_usercopy(void) * set and we are preemptible. The hack here is to schedule a * decrementer to fire here and reschedule for us if necessary. */ - if (IS_ENABLED(CONFIG_PREEMPT) && need_resched()) + if (IS_ENABLED(CONFIG_PREEMPTION) && need_resched()) set_dec(1); return 0; }
-- ankur