On 10/25/16 at 08:42pm, Pratyush Anand wrote:
> > > With -d 1:
> > > Trial 1: 2768.424565806 S
> > > Trial 2: 2749.622115455 S
> > > Trail 3: 2537.770359073 S
> >
> > Could you increase the number of trials ?
>
> OK, I can do that. Might take some time, as I will have to arrange that high
> memory machine again.
>
> > If the average time is close to the results of Trial 1 (2768s) and 2 (2749s),
> > the regression rate is 8% and it sounds neither large nor small.
> > If the average is a level of 2500s like Trial 3, it's ideal.
> >
> > > Signed-off-by: Pratyush Anand <panand at redhat.com>
> > > ---
> > > arch/x86_64.c | 42 ++++++++----------------------------------
> > > makedumpfile.h | 4 ++--
> > > 2 files changed, 10 insertions(+), 36 deletions(-)
> > >
> > > diff --git a/arch/x86_64.c b/arch/x86_64.c
> > > index a96fd8ae00a1..fe2764a8bec2 100644
> > > --- a/arch/x86_64.c
> > > +++ b/arch/x86_64.c
> > > @@ -203,6 +203,12 @@ vtop4_x86_64(unsigned long vaddr)
> > > {
> > > unsigned long page_dir, pml4, pgd_paddr, pgd_pte, pmd_paddr, pmd_pte;
> > > unsigned long pte_paddr, pte;
> > > + unsigned long phys_base;
> > > +
> > > + if (SYMBOL(phys_base) != NOT_FOUND_SYMBOL)
> > > + phys_base = info->phys_base;
> > > + else
> > > + phys_base = 0;
> > >
> > > if (SYMBOL(init_level4_pgt) == NOT_FOUND_SYMBOL) {
> > > ERRMSG("Can't get the symbol of init_level4_pgt.\n");
> > > @@ -212,9 +218,9 @@ vtop4_x86_64(unsigned long vaddr)
> > > /*
> > > * Get PGD.
> > > */
> > > - page_dir = SYMBOL(init_level4_pgt);
> > > + page_dir = SYMBOL(init_level4_pgt) - __START_KERNEL_map + phys_base;
> >
> > I want to confirm that this VA to PA translation is always safe,
> > otherwise we should do the condition check which was done in
> > vaddr_to_paddr_x86_64(), isn't it ?
> >
>
> I think this should be safe, however x86 expert can comment better. Baoquan
> any comment here?
Yes, I think this is safe. Below is the physical to virtual address
translation function in x86 64. And init_level4_pgt is a global variable
located in kernel text region.
arch/x86/include/asm/page_64.h
static inline unsigned long __phys_addr_nodebug(unsigned long x)
{
unsigned long y = x - __START_KERNEL_map;
/* use the carry flag to determine if x was < __START_KERNEL_map */
x = y + ((x > y) ? phys_base : (__START_KERNEL_map - PAGE_OFFSET));
return x;
}
