Re: [PATCH] arch, mm: introduce arch_tlb_gather_mmu_lazy (was: Re: [RESEND PATCH] mm, oom_reaper: gather each vma to prevent) leaking TLB entry

Michal Hocko
2017-11-13T09:51:13Z

On Mon 13-11-17 09:28:33, Minchan Kim wrote:
[...]
> Thanks for the patch, Michal.
> However, it would be nice to do it tranparently without asking
> new flags from users.
>
> When I read tlb_gather_mmu's description, fullmm is supposed to
> be used only if there is no users and full address space.
>
> That means we can do it API itself like this?
>
> void arch_tlb_gather_mmu(...)
>
> tlb->fullmm = !(start | (end + 1)) && atomic_read(&mm->mm_users) == 0;

I do not have a strong opinion here. The optimization is quite subtle so
calling it explicitly sounds like a less surprising behavior to me
longterm. Note that I haven't checked all fullmm users.

--
Michal Hocko
SUSE Labs