On 2024-11-17 00:53:06 [+0530], Shrikanth Hegde wrote: > 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. > > Not checking for lazy bit here, since it could lead to unnecessary > context switches. > > Suggested-by: Sebastian Andrzej Siewior <bige...@linutronix.de> > Signed-off-by: Shrikanth Hegde <sshe...@linux.ibm.com> > --- > 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);
Now looking at this again there is a comment why preempt_enable() is bad. An interrupt between preempt_enable_no_resched() and set_dec() is fine because irq-exit would preempt properly? Regular preemption works again once copy_to_user() is done? So if you copy 1GiB, you are blocked for that 1GiB? > return 0; > } Sebastian
