Messages in this thread Patch in this message | | | Date | Thu, 23 Jun 2005 17:06:35 +1000 | From | Nick Piggin <> | Subject | [patch][rfc] 2/5: micro optimisation for mm/rmap.c |
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2/5 Microoptimise page_add_anon_rmap. Although these expressions are used only in the taken branch of the if() statement, the compiler can't reorder them inside because atomic_inc_and_test is a barrier.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Index: linux-2.6/mm/rmap.c =================================================================== --- linux-2.6.orig/mm/rmap.c +++ linux-2.6/mm/rmap.c @@ -442,22 +442,23 @@ int page_referenced(struct page *page, i void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address) { - struct anon_vma *anon_vma = vma->anon_vma; - pgoff_t index; - BUG_ON(PageReserved(page)); - BUG_ON(!anon_vma); inc_mm_counter(vma->vm_mm, anon_rss); - anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; - index = (address - vma->vm_start) >> PAGE_SHIFT; - index += vma->vm_pgoff; - index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT; - if (atomic_inc_and_test(&page->_mapcount)) { - page->index = index; + struct anon_vma *anon_vma = vma->anon_vma; + pgoff_t index; + + BUG_ON(!anon_vma); + anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; page->mapping = (struct address_space *) anon_vma; + + index = (address - vma->vm_start) >> PAGE_SHIFT; + index += vma->vm_pgoff; + index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT; + page->index = index; + inc_page_state(nr_mapped); } /* else checking page index and mapping is racy */ | |