Messages in this thread | | | Date | Thu, 3 Feb 2011 13:46:26 -0800 (PST) | From | David Rientjes <> | Subject | Re: [RFC][PATCH 2/6] pagewalk: only split huge pages when necessary |
| |
On Thu, 3 Feb 2011, Dave Hansen wrote:
> > > diff -puN mm/pagewalk.c~pagewalk-dont-always-split-thp mm/pagewalk.c > > > --- linux-2.6.git/mm/pagewalk.c~pagewalk-dont-always-split-thp 2011-01-27 10:57:02.309914973 -0800 > > > +++ linux-2.6.git-dave/mm/pagewalk.c 2011-01-27 10:57:02.317914965 -0800 > > > @@ -33,19 +33,35 @@ static int walk_pmd_range(pud_t *pud, un > > > > > > pmd = pmd_offset(pud, addr); > > > do { > > > + again: > > > > checkpatch will warn about the indent. > > > > > next = pmd_addr_end(addr, end); > > > - split_huge_page_pmd(walk->mm, pmd); > > > - if (pmd_none_or_clear_bad(pmd)) { > > > + if (pmd_none(*pmd)) { > > > > Not sure why this has been changed from pmd_none_or_clear_bad(), that's > > been done even prior to THP. > > The bad check will trigger on huge pmds. We can not use it here. We > can, however, use pmd_none(). The bad check was moved below to where we > actually dereference the pmd. >
Ah, right, thanks.
> > > if (walk->pte_hole) > > > err = walk->pte_hole(addr, next, walk); > > > if (err) > > > break; > > > continue; > > > } > > > + /* > > > + * This implies that each ->pmd_entry() handler > > > + * needs to know about pmd_trans_huge() pmds > > > + */ > > > > Probably needs to be documented somewhere for users of pagewalk? > > Probably, but we don't currently have any central documentation for it. > Guess we could make some, or just ensure that all the users got updated. > Any ideas where to put it other than the mm_walk struct? >
I think noting it where struct mm_walk is declared would be best (just a "/* must handle pmd_trans_huge() */" would be sufficient) although eventually it might be cleaner to add a ->pmd_huge_entry().
| |