Dave Hansen wrote:
> On 05/11/2013 06:23 PM, Kirill A. Shutemov wrote:
> > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> >
> > As with add_to_page_cache_locked() we handle HPAGE_CACHE_NR pages a
> > time.
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > ---
> > mm/filemap.c | 31 +++++++++++++++++++++++++------
> > 1 file changed, 25 insertions(+), 6 deletions(-)
> >
> > diff --git a/mm/filemap.c b/mm/filemap.c
> > index b0c7c8c..657ce82 100644
> > --- a/mm/filemap.c
> > +++ b/mm/filemap.c
> > @@ -115,6 +115,9 @@
> > void __delete_from_page_cache(struct page *page)
> > {
> > struct address_space *mapping = page->mapping;
> > + bool thp = PageTransHuge(page) &&
> > + IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE);
> > + int nr;
>
> Is that check for the config option really necessary? How would we get
> a page with PageTransHuge() set without it being enabled?
I'll drop it and use hpagecache_nr_page() instead.
> I like to rewrite your code. :)
It's nice. Thanks.
> Which reminds me... Why do we handle their reference counts differently? :)
>
> It seems like we could easily put a for loop in delete_from_page_cache()
> that will release their reference counts along with the head page.
> Wouldn't that make the code less special-cased for tail pages?
delete_from_page_cache() is not the only user of
__delete_from_page_cache()...
It seems I did it wrong in add_to_page_cache_locked(). We shouldn't take
references on tail pages there, only one on head. On split it will be
distributed properly.
> > /* Leave page->index set: truncation lookup relies upon it */
> > - mapping->nrpages--;
> > - __dec_zone_page_state(page, NR_FILE_PAGES);
> > + mapping->nrpages -= nr;
> > + __mod_zone_page_state(page_zone(page), NR_FILE_PAGES, -nr);
> > if (PageSwapBacked(page))
> > - __dec_zone_page_state(page, NR_SHMEM);
> > + __mod_zone_page_state(page_zone(page), NR_SHMEM, -nr);
> > BUG_ON(page_mapped(page));
>
> Man, we suck:
>
> __dec_zone_page_state()
> and
> __mod_zone_page_state()
>
> take a differently-typed first argument. <sigh>
>
> Would there be any good to making __dec_zone_page_state() check to see
> if the page we passed in _is_ a compound page, and adjusting its
> behaviour accordingly?
Yeah, it would be better but I think it outside the scope of the patchset.
Probably, later.
--
Kirill A. Shutemov
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