On Fri, Aug 2, 2013 at 12:17 AM, Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> wrote: > Hillf Danton <dhillf@xxxxxxxxx> writes: > >> On Wed, Jul 31, 2013 at 2:37 PM, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote: >>> On Wed, Jul 31, 2013 at 02:21:38PM +0800, Hillf Danton wrote: >>>> On Wed, Jul 31, 2013 at 12:41 PM, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote: >>>> > On Wed, Jul 31, 2013 at 10:49:24AM +0800, Hillf Danton wrote: >>>> >> On Wed, Jul 31, 2013 at 10:27 AM, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote: >>>> >> > On Mon, Jul 29, 2013 at 03:24:46PM +0800, Hillf Danton wrote: >>>> >> >> On Mon, Jul 29, 2013 at 1:31 PM, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote: >>>> >> >> > alloc_huge_page_node() use dequeue_huge_page_node() without >>>> >> >> > any validation check, so it can steal reserved page unconditionally. >>>> >> >> >>>> >> >> Well, why is it illegal to use reserved page here? >>>> >> > >>>> >> > If we use reserved page here, other processes which are promised to use >>>> >> > enough hugepages cannot get enough hugepages and can die. This is >>>> >> > unexpected result to them. >>>> >> > >>>> >> But, how do you determine that a huge page is requested by a process >>>> >> that is not allowed to use reserved pages? >>>> > >>>> > Reserved page is just one for each address or file offset. If we need to >>>> > move this page, this means that it already use it's own reserved page, this >>>> > page is it. So we should not use other reserved page for moving this page. >>>> > >>>> Hm, how do you determine "this page" is not buddy? >>> >>> If this page comes from the buddy, it doesn't matter. It imply that >>> this mapping cannot use reserved page pool, because we always allocate >>> a page from reserved page pool first. >>> >> A buddy page also implies, if the mapping can use reserved pages, that no >> reserved page was available when requested. Now we can try reserved >> page again. > > I didn't quiet get that. My understanding is, the new page we are Neither did I ;) > allocating here for soft offline should not be allocated from the > reserve pool. If we do that we may possibly have allocation failure > later for a request that had done page reservation. Now to > avoid that we make sure we have enough free pages outside reserve pool > so that we can dequeue the huge page. If not we use buddy to allocate > the hugepage. > What if it is a mapping with HPAGE_RESV_OWNER set? Or can we block owner from using any page available here? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>