Re: [RFC, PATCHv1 00/28] 5-level paging

From: Dave Hansen
Date: Fri Dec 09 2016 - 11:49:53 EST

On 12/09/2016 02:37 AM, Kirill A. Shutemov wrote:
> On other hand, large virtual address space would put more pressure on
> cache -- at least one more page table per process, if we make 56-bit VA
> default.

For a process only using a small amount of its address space, the
mid-level paging structure caches will be very effective since the page
walks are all very similar. You may take a cache miss on the extra
level on the *first* walk, but you only do that once per context switch.
I bet the CPU is also pretty aggressive about filling those things when
it sees a new CR3 and they've been forcibly emptied. So, you may never
even _see_ the latency from that extra miss.