Re: [PATCH 16/19] thp: update documentation
From: Kirill A. Shutemov
Date: Wed Nov 19 2014 - 08:12:01 EST
On Wed, Nov 19, 2014 at 08:07:59AM +0000, Naoya Horiguchi wrote:
> On Wed, Nov 05, 2014 at 04:49:51PM +0200, Kirill A. Shutemov wrote:
> > The patch updates Documentation/vm/transhuge.txt to reflect changes in
> > THP design.
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > ---
> > Documentation/vm/transhuge.txt | 84 +++++++++++++++++++-----------------------
> > 1 file changed, 38 insertions(+), 46 deletions(-)
> > diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt
> > index df1794a9071f..33465e7b0d9b 100644
> > --- a/Documentation/vm/transhuge.txt
> > +++ b/Documentation/vm/transhuge.txt
> > @@ -200,9 +200,18 @@ thp_collapse_alloc_failed is incremented if khugepaged found a range
> > of pages that should be collapsed into one huge page but failed
> > the allocation.
> > -thp_split is incremented every time a huge page is split into base
> > +thp_split_page is incremented every time a huge page is split into base
> > pages. This can happen for a variety of reasons but a common
> > reason is that a huge page is old and is being reclaimed.
> > + This action implies splitting all PMD the page mapped with.
> > +
> > +thp_split_page_failed is is incremented if kernel fails to split huge
> 'is' appears twice.
> > + page. This can happen if the page was pinned by somebody.
> > +
> > +thp_split_pmd is incremented every time a PMD split into table of PTEs.
> > + This can happen, for instance, when application calls mprotect() or
> > + munmap() on part of huge page. It doesn't split huge page, only
> > + page table entry.
> > thp_zero_page_alloc is incremented every time a huge zero page is
> > successfully allocated. It includes allocations which where
> There is a sentense related to the adjustment on futex code you just
> removed in patch 15/19 in "get_user_pages and follow_page" section.
> split_huge_page() to avoid the head and tail pages to disappear from
> under it, see the futex code to see an example of that, hugetlbfs also
> needed special handling in futex code for similar reasons).
> this seems obsolete, so we need some change on this?
I'll update documentation futher once patchset will be closer to ready
Kirill A. Shutemov
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