Date: Mon, 22 Mar 2010 16:06:33 +0100 From: Olivier Houchard <cognet@freebsd.org> To: Mark Tinguely <tinguely@casselton.net> Cc: freebsd-arm@freebsd.org Subject: Re: Performance of SheevaPlug on 8-stable Message-ID: <20100322150633.GA18277@ci0.org> In-Reply-To: <201003221455.o2MEt4V5068925@casselton.net> References: <4B951CE2.6040507@semihalf.com> <201003221455.o2MEt4V5068925@casselton.net>
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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
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