RE: Prefetch mmap_sem in ia64_do_page_fault()

["Chen, Kenneth W" <kenneth.w.chen@intel.com>]

Chen, Kenneth W wrote on Tuesday, March 28, 2006 11:32 PM
> Christoph Lameter wrote on Tuesday, March 28, 2006 11:16 PM
> > 
> > I saw David Mosberger's patch from last year
> > 
> > and it seems that he implemented fast handling of these NULL cases?
> 
> I know about that patch and I'm referring in the context of that commit:
> 
> ld8.s r1=[r0]      - immediate nat generation, no fault
> lfetch.fault [r0]  - generate nat page consumption because lfetch is not
>                      considered as a speculative access.
> 
> The nat page consumption fault handler should be rather quick, though cpu
> still have to fault into the handler, muck around with ipsr.ed bit and
> then rfi.  What I'm saying is there is an even *faster* way of doing
> prefetch.

One other caveat with this is that if you have a tlb miss on mm->mmap_sem,
it won't prefetch anything because alt_dtlb_miss handler will nuke the
ld8.s or lfetch instruction :-(

- Ken