Hi Peter, thanks for reviewing this! On Fri, May 08, 2020 at 09:20:00PM +0200, Peter Zijlstra wrote: > The only concern I have is the pgd_lock lock hold times. > > By not doing on-demand faults anymore, and consistently calling > sync_global_*(), we iterate that pgd_list thing much more often than > before if I'm not mistaken. Should not be a problem, from what I have seen this function is not called often on x86-64. The vmalloc area needs to be synchronized at the top-level there, which is by now P4D (with 4-level paging). And the vmalloc area takes 64 entries, when all of them are populated the function will not be called again. On 32bit it might be called more often, because synchronization happens on the PMD level, which is also used for large-page mapped ioremap regions. But these don't happen very often and there are also no VMAP stacks on x86-32 which could cause this function to be called frequently. Joerg
