On Tue, 29 Apr 2008 10:10:58 -0400 Tony Battersby <tonyb@cybernetics.com> wrote:Hmm, my idea is below. Nick's remove ZERO_PAGE patch includes following change == @@ -2252,39 +2158,24 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, spinlock_t *ptl; { <snip> - page_add_new_anon_rmap(page, vma, address); - } else { - /* Map the ZERO_PAGE - vm_page_prot is readonly */ - page = ZERO_PAGE(address); - page_cache_get(page); - entry = mk_pte(page, vma->vm_page_prot); + if (unlikely(anon_vma_prepare(vma))) + goto oom; + page = alloc_zeroed_user_highpage_movable(vma, address); == above change is for avoiding to use ZERO_PAGE at read-page-fault to anonymous vma. This is reasonable I think. But at coredump, tons of read-but-never-written pages can be allocated. == coredump -> get_user_pages() -> follow_page() returns NULL -> handle mm fault -> do_anonymous page. == follow_page() returns ZERO_PAGE only when page table is not avaiable. So, making follow_page() return ZERO_PAGE can be a fix of extra memory consumpstion at core dump. (Maybe someone can think of other fix.) how about this patch ? Could you try ? (I'm sorry but I'll not be active for a week because my servers are powered off.) -Kame == follow_page() returns ZERO_PAGE if page table is not available. but returns NULL pte is not presentl. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Index: linux-2.6.25/mm/memory.c =================================================================== --- linux-2.6.25.orig/mm/memory.c +++ linux-2.6.25/mm/memory.c @@ -926,15 +926,15 @@ struct page *follow_page(struct vm_area_ page = NULL; pgd = pgd_offset(mm, address); if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd))) - goto no_page_table; + goto null_or_zeropage; pud = pud_offset(pgd, address); if (pud_none(*pud) || unlikely(pud_bad(*pud))) - goto no_page_table; + goto null_or_zeropage; pmd = pmd_offset(pud, address); if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd))) - goto no_page_table; + goto null_or_zeropage; if (pmd_huge(*pmd)) { BUG_ON(flags & FOLL_GET); @@ -947,8 +947,10 @@ struct page *follow_page(struct vm_area_ goto out; pte = *ptep; - if (!pte_present(pte)) - goto unlock; + if (!(flags & FOLL_WRITE) && !pte_present(pte)) { + pte_unmap_unlock(ptep, ptl); + goto null_or_zeropage; + } if ((flags & FOLL_WRITE) && !pte_write(pte)) goto unlock; page = vm_normal_page(vma, address, pte); @@ -968,7 +970,7 @@ unlock: out: return page; -no_page_table: +null_or_zeropage: /* * When core dumping an enormous anonymous area that nobody * has touched so far, we don't want to allocate page tables. --
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| Gerrit Renker | [PATCH 27/37] dccp: Integration of dynamic feature activation - part 2 (server side) |
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