Re: [PATCH 4/5] powernv:idle: Move initialization of sibling pacas to pnv_alloc_idle_core_states

Nicholas Piggin [off-list ref] writes:

On Fri, 7 Jul 2017 20:34:16 +0530
Gautham R Shenoy [off-list ref] wrote:

quoted

On Fri, Jul 07, 2017 at 01:16:09AM +1000, Nicholas Piggin wrote:

quoted

Speaking of which... core_idle_state and thread_sibling_pacas are
allocated with kmalloc_node... What happens if we take an SLB miss
in the idle wakeup code on these guys? Nothing good I think. Perhaps
we should put them into the pacas or somewhere in bolted memory.  

Yes, though the SLB miss hasn't yet been encountered in practise so
far!

Considering it's a node-affine allocation, it may actually be possible
to hit in practice on very large memory systems in practice.

You can boot with disable_1tb_segments on the kernel command line to
increase the change of hitting it.

cheers