Re: [RFC] recursive pagetables for x86 PAE

William Lee Irwin III
2003-06-14T13:49:27Z

Am Freitag, 13. Juni 2003 23:47 schrieb Dave Hansen:
>> When you have lots of tasks, the pagetables start taking up lots of
>> lowmem. We have the ability to push the PTE pages into highmem, but
>> that exacts a penalty from the atomic kmaps which, depending on
>> workload, can be a 10-15% performance hit.
>> The following patches implement something which we like to call UKVA.
>> It's a Kernel Virtual Area which is private to a process, just like
>> Userspace. You can put any process-local data that you want in the
>> area. But, for now, I just put PTE pages in there.

On Sat, Jun 14, 2003 at 01:27:48PM +0200, Oliver Neukum wrote:
> If you put only such pages there, do you really want that memory to
> be per task? IMHO it should be per memory context to aid threading
> performance.

Per-process is essentially per-mm.

On Sat, Jun 14, 2003 at 01:27:48PM +0200, Oliver Neukum wrote:
> Secondly, doesn't this scream for using large pages?

No, 2MB/4MB pages are not useful here.

-- wli