Messages in this thread | | | Date | Tue, 18 Apr 2006 09:42:12 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 5/5] Swapless V2: Revise main migration logic |
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On Mon, 17 Apr 2006 17:27:48 -0700 (PDT) Christoph Lameter <clameter@sgi.com> wrote:
> On Tue, 18 Apr 2006, KAMEZAWA Hiroyuki wrote: > > > Then, > > > > if (is_migration_entry(entry)) { > > change_to_read_migration_entry(entry); > > copy_entry(entry); > > } > > > > is sane. > > Hmmm... Looks like I need to do the patch. Is the following okay? This > will also only work on cow mappings. > I think okay.
BTW, when copying mm, mm->mmap_sem is held. Is mm->mmap_sem is not held while page migraion now ? I'm sorry I can't catch up all changes. or Is this needed for lazy migration (migration-on-fault) ?
-Kame
> > > Read/Write migration entries: Implement correct behavior in copy_one_pte > > Migration entries with write permission must become SWP_MIGRATION_READ > entries if a COW mapping is processed. The migration entries from which > the copy is being made must also become SWP_MIGRATION_READ. This mimicks > the copying of pte for an anonymous page. > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > Signed-off-by: Christoph Lameter <clameter@sgi.com> > > Index: linux-2.6.17-rc1-mm2/mm/memory.c > =================================================================== > --- linux-2.6.17-rc1-mm2.orig/mm/memory.c 2006-04-17 16:23:50.000000000 -0700 > +++ linux-2.6.17-rc1-mm2/mm/memory.c 2006-04-17 17:25:50.000000000 -0700 > @@ -434,7 +434,9 @@ copy_one_pte(struct mm_struct *dst_mm, s > /* pte contains position in swap or file, so copy. */ > if (unlikely(!pte_present(pte))) { > if (!pte_file(pte)) { > - swap_duplicate(pte_to_swp_entry(pte)); > + swp_entry_t entry = pte_to_swp_entry(pte); > + > + swap_duplicate(entry); > /* make sure dst_mm is on swapoff's mmlist. */ > if (unlikely(list_empty(&dst_mm->mmlist))) { > spin_lock(&mmlist_lock); > @@ -443,6 +445,19 @@ copy_one_pte(struct mm_struct *dst_mm, s > &src_mm->mmlist); > spin_unlock(&mmlist_lock); > } > + if (is_migration_entry(entry) && > + is_cow_mapping(vm_flags)) { > + page = migration_entry_to_page(entry); > + > + /* > + * COW mappings require pages in both parent > + * and child to be set to read. > + */ > + entry = make_migration_entry(page, > + ` SWP_MIGRATION_READ); > + pte = swp_entry_to_pte(entry); > + set_pte_at(src_mm, addr, src_pte, pte); > + } > } > goto out_set_pte; > } >
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