On Thu, Jun 22, 2023 at 09:47:22AM -0300, Marcelo Tosatti wrote:

quoted

there's patches that cure the thp abuse of this.

The other case where the IPI can happen is:

CPU-0                                   CPU-1

tlb_remove_table
tlb_remove_table_sync_one
IPI
                                        local_irq_disable
                                        gup_fast
                                        local_irq_enable


So its not only the THP case.

(your CPU-1 thing is wholly irrelevant)

Well, I know, but this case *should* be exceedingly rare. Last time
around I asked why you all were tripping this, you pointed at the THP
case.

The THP case should be fixed along the lines of Jann's original patches.

If you can trip this at any significant rate, then we should probably
look at a better allocation scheme. It means you're really low on
memory.