Messages in this thread | | | Subject | Re: [patch 2/3] vmscan: drop page_mapping_inuse() | From | Minchan Kim <> | Date | Tue, 23 Feb 2010 23:03:20 +0900 |
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On Mon, 2010-02-22 at 20:49 +0100, Johannes Weiner wrote: > page_mapping_inuse() is a historic predicate function for pages that > are about to be reclaimed or deactivated. > > According to it, a page is in use when it is mapped into page tables > OR part of swap cache OR backing an mmapped file. > > This function is used in combination with page_referenced(), which > checks for young bits in ptes and the page descriptor itself for the > PG_referenced bit. Thus, checking for unmapped swap cache pages is > meaningless as PG_referenced is not set for anonymous pages and > unmapped pages do not have young ptes. The test makes no difference.
Nice catch!
> > Protecting file pages that are not by themselves mapped but are part > of a mapped file is also a historic leftover for short-lived things
I have been a question in the part. You seem to solve my long question. :) But I want to make sure it by any log. Could you tell me where I find the discussion mail thread or git log at that time?
Just out of curiosity.
> like the exec() code in libc. However, the VM now does reference > accounting and activation of pages at unmap time and thus the special > treatment on reclaim is obsolete.
It does make sense.
> > This patch drops page_mapping_inuse() and switches the two callsites > to use page_mapped() directly. > > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> > --- > mm/vmscan.c | 25 ++----------------------- > 1 files changed, 2 insertions(+), 23 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index c2db55b..a8e4cbe 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -262,27 +262,6 @@ unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, > return ret; > } > > -/* Called without lock on whether page is mapped, so answer is unstable */ > -static inline int page_mapping_inuse(struct page *page) > -{ > - struct address_space *mapping; > - > - /* Page is in somebody's page tables. */ > - if (page_mapped(page)) > - return 1; > - > - /* Be more reluctant to reclaim swapcache than pagecache */ > - if (PageSwapCache(page)) > - return 1; > - > - mapping = page_mapping(page); > - if (!mapping) > - return 0; > - > - /* File is mmap'd by somebody? */ > - return mapping_mapped(mapping); > -} > - > static inline int is_page_cache_freeable(struct page *page) > { > /* > @@ -603,7 +582,7 @@ static enum page_references page_check_references(struct page *page, > if (vm_flags & VM_LOCKED) > return PAGEREF_RECLAIM; > > - if (page_mapping_inuse(page)) > + if (page_mapped(page)) > return PAGEREF_ACTIVATE; > > /* Reclaim if clean, defer dirty pages to writeback */ > @@ -1378,7 +1357,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone, > } > > /* page_referenced clears PageReferenced */ > - if (page_mapping_inuse(page) && > + if (page_mapped(page) && > page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { > nr_rotated++; > /*
It's good to me. But page_referenced already have been checked page_mapped. How about folding alone page_mapped check into page_referenced's inner?
-- Kind regards, Minchan Kim
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