Performance of SheevaPlug on 8-stable

[Olivier Houchard]

On Mon, Mar 22, 2010 at 09:55:04AM -0500, Mark Tinguely wrote:
> On Mon, 08 Mar 2010 16:50:58, Grzegorz Bernacki said:
> 
> >  This is probably caused by mechanism which turns of cache for shared pages.
> >  When I add applied following path:
> >
> >  diff --git a/sys/arm/arm/pmap.c b/sys/arm/arm/pmap.c
> >  index 390dc3c..d17c0cc 100644
> >  --- a/sys/arm/arm/pmap.c
> >  +++ b/sys/arm/arm/pmap.c
> >  @@ -1401,6 +1401,8 @@ pmap_fix_cache(struct vm_page *pg, pmap_t pm, vm_offset_t va)
> >            */
> >
> >           TAILQ_FOREACH(pv, &pg->md.pv_list, pv_list) {
> >  +               if (pv->pv_flags & PVF_EXEC)
> >  +                       return;
> >                           /* generate a count of the pv_entry uses */
> >                   if (pv->pv_flags & PVF_WRITE) {
> >                           if (pv->pv_pmap == pmap_kernel())
> >
> >  execution time of 'test' program is:
> >  mv78100-4# time ./test
> >  5.000u 0.000s 0:05.40 99.8%     40+1324k 0+0io 0pf+0w
> >
> >  and without this path is:
> >  mv78100-4# time ./test
> >  295.000u 0.000s 4:56.01 99.7%   40+1322k 0+0io 0pf+0w
> >
> >
> >  I think we need to handle executable pages in different way.
> >
> >  grzesiek
> 
> Good going Oliver and thank-you on the pmap_enter_pv kernel map patch Revision
> 205425.
> 
> Last week, before this patch, Maks Verver was so kind to put some statements
> in the VM (vm_page_free_toq()) for the SheevaPlug because I could not cause
> these paths with the Gumstix emulator. Maks, could you add to
> vm_phys_free_pages():
> 
> 	if (m->md.pv_kva)
> +	{
> +		printf("vm_phys_free_pages: md.pv_kva 0x%08x\n", m->md.pv_kva);
> 		m->md.pv_kva = 0;
> +	}
> 
> Even on the Gumstix emulator with the current patch, pmap_fix_cache() still
> has many executable pages that have both a kernel and user pv_entry. Looks
> like something like the above patch is still needed.
> 

I added a few printf and saw the same thing, however isn't assuming we 
shouldn't modify the cache settings if the page is executable a bit dangerous ?
Or did I misread your patch ?

Olivier